Guide to the Odonata of central Ñeembucú, Paraguay: indicator species of wetland habitats

The department of Ñeembucú, in south-western Paraguay, is home to the virtually unexplored Ñeembucú Wetlands, the second largest wetland system in the country, representing a major gap in biodiversity knowledge. As organisms ubiquitous with wetlands, the Odonata, or dragonflies (Anisoptera) and damselflies (Zygoptera), have the potential to be effective indicators of wetland habitats in the face of increasing anthropogenic impacts in the region. We therefore comprehensively surveyed the Odonata in central Ñeembucú over a period of two years using a listing method. Here, we present an annotated checklist and identification key to the species present in central Ñeembucú with details on their habitat preferences, phenology and behaviour. We found 60 species but estimate a total of between 62 and 90 species. Eleven (18%) are new records for Paraguay. Species composition is similar to the Argentine Humid Chaco, with four bioregional endemics, whilst representatives from the Andean-Patagonian subregion are present in open areas. Such partitioning of species from different bioregions into different habitats is typical of ecotonal regions. Two further species are endemic to the Paraná-Paraguay basin and three are highly localised, indicating the high conservation value of the Ñeembucú Wetlands. Eleven species have the potential to be effective indicators of the Paraguay River, large permanent wetlands, grassy temporary wetlands and wooded temporary wetlands, providing an effective tool to identify critical wetland ecosystems in the face of the growing threats from human activities. We also provide recommendations for the protection and management of wetlands in the region.


Introduction
Shortfalls in the knowledge of species taxonomy, distribution, abundance and tolerances present major setbacks to our understanding of patterns in biodiversity, hindering conservation planning and ecological and evolutionary studies (Hortal et al., 2015), particularly in understudied regions. Lying between some of the most biodiverse countries on earth, the small, landlocked country of Paraguay is one such overlooked region. Although it was home to some of the earliest expeditions to document natural history in South America, very little progress has since been made. Nevertheless, it has an exceptionally high level of biodiversity relative to its small size and shallow relief due to its position at the meeting point of five of the continent's terrestrial biomes (Olson et al., 2001) and four freshwater ecoregions (Hales & Petry, 2015). Within this context, the department of Ñeembucú, sandwiched between the Paraná and Paraguay rivers in the south-west corner of the country, is one of the least explored regions of Paraguay (Mereles et al., 2005). The landscape is dominated by wetlands and flood-prone habitats, covering up to 90% of *Corresponding author. Email: jerdickens@gmail.com the area (Contreras Roqué, Contreras Chialchia, & Delpino Aguayo, 2007), including the second largest wetland complex in the country after the Pantanal, known as the Ñeembucú Wetlands or Esteros del Ñeembucú (Neiff, 2001). Much of the department is also in a near-pristine state with low human population density, making it a haven for aquatic species such as the Odonata, or dragonflies (Anisoptera) and damselflies (Zygoptera).
The Odonata are an ancient order of insects dating back to the Permian (Suhling et al., 2015). Adults are supreme aerial predators among invertebrates, flying with unrivalled speed and agility, but larvae are aquatic, a characteristic that closely ties most species to aquatic habitats. They are among the best-studied groups of insects (Suhling et al., 2015) with 5700 known species, although the actual total is estimated to be closer to 7000. The Neotropical region is the most species-rich, with over 1727 species, followed closely by the Oriental region, with 1703 species (Kalkman et al., 2008;Von Ellenrieder, 2009a). However, the Neotropics also suffer the greatest deficit in knowledge (Kalkman et al., 2008), with the rate of species discovery outstripping the rate at which new species are described (Paulson, 2004). Between 1984 and, an average of just 16 new species were described annually (Paulson, 2004;Von Ellenrieder 2009a). Additionally, the vast majority of species are known from only a handful of localities, and surveys are still required for most regions, with several large areas remaining completely unsampled (Von Ellenrieder, 2009a). One of the largest of these is the Chaco biome, shared between Paraguay, Bolivia and Argentina (Paulson, 2004). Although  and Rodríguez & Molineri (2013) recently conducted surveys in the Argentine portion, the Paraguayan and Bolivian portions remain unexplored (Kalkman et al., 2008;Von Ellenrieder, 2009a). In Paraguay, 133 Odonata species are known, almost all of which are from the eastern portion of the country, eight of which are endemic (Paulson, 2004). This is about half the number occurring in neighbouring Brazilian states and Argentina (Bedê, Machado, Piper, & Souza, 2015), so is likely greatly underestimated given the lack of recent surveys and the majority of the country remaining completely unexplored, thus representing a major deficit in the knowledge of the species present.
In addition to this lack of knowledge, the natural ecosystems of the region are now facing unprecedented threats as a result of wetland drainage, changes in the flood regime caused by improper road design and construction, uncontrolled agrochemical use, deteriorating water quality, chronic overgrazing and proliferation of feral animals (Aveiro-Talavera, n.d.; Contreras Roqué et al., 2007). This is especially alarming given the important role wetlands play in ecosystem function through water provision, floodwater attenuation, water quality amelioration, groundwater recharge, increased productivity and biodiversity maintenance (Acreman & Mountford, 2009;Maltby, 2009). At a regional scale, the Ñeembucú Wetlands also play a vital role in maintaining connectivity between a chain of wetlands running along the main channel of the Paraguay-Parana river system (Neiff, 2001), including the Pantanal Wetlands, Western Chaco Wetlands, Humid Chaco Wetlands, Ibera Wetlands, and Parana River Delta (Figure 1). In addition to their ecological importance, they underlie the socio-economic stability of the region, which relies almost entirely on aquatic resources for energy generation, trade (via shipping), food security (through fisheries and replenishment of fertile soils) and water provision (Quirós, 2003). Given their central role in maintaining ecological and socio-economic stability in the region, their conservation is critical.
In light of this, the Odonata are highly suitable for use as indicator species to monitor changes in wetland habitats by providing a measure of ecosystem health based on the species present (Clark & Samways, 1996;Golfieri et al. 2016;Samways, 2008). This is because they are widespread and relatively diverse in wetland habitats, vary in their level of sensitivity to disturbances (including changes in water quality, substrate and vegetation structure) and are able to respond rapidly to disturbances due to their short life-cycle and high mobility as adults (Clark & Samways, 1996;Golfieri, Hardersen, Maiolini, & Surian, 2016;Samways, 2008). They are also conspicuous and more easily sampled and identified than most other groups of aquatic insects (Brown, 1991;Clark & Samways, 1996;Kutcher & Bried, 2014). Furthermore, Valente-Neto, De Oliveira Roque, Rodrigues, Juen, and Swan (2016) found that monitoring of adults alone sufficed in capturing effects on both adults and larvae. However, in order for changes in the environment to be interpreted from changes in species assemblage structure, the natural assemblages and species preferences must be known (Clark & Samways, 1996). Therefore, to improve the state of knowledge about the region, we undertook a comprehensive survey of the Odonata. This is the first such survey of Odonata in Paraguay and the first for the Humid Chaco outside of Argentina. As such, we present our findings in the form of a practical field guide with a comprehensive annotated checklist and key to all species recorded in central Ñeembucú, along with information on their distribution, habitat preferences, phenology and behaviour. We also provide suitable indicator species for the major wetland types in the region.

Study site
The department of Ñeembucú lies in the south-west corner of Paraguay, separated from Argentina by the Paraguay River to the west and Paraná River to the south. It is extremely flat and consists almost entirely of a large sedimentary plain known as the Yabebyry formation (Duarte, 2000), which is characterised by poorly drained soils that support hydrophilic grasslands and savannahs of the Humid Chaco, including wooded thickets and palm savannah (Dinerstein et al., 1995;Olson et al., 2001). These areas are interspersed by the loessic sediments of the Ñeembucú formation that support a mosaic of grassland and gallery forest habitats and the iconic permanent wetlands of the Ñeembucú Wetlands, covering an area of 4000-8000 km 2 . Their extent varies according to annual rainfall, which cycles between wet and dry phases, corresponding to the El Niño-Southern Oscillation (ENSO), with a 2. 5-3.7 year oscillation and [8][9][10][11] year periodicity (Contreras, 2003). We carried out this study during a wet phase marked by extensive flooding. The climate is warm temperate, fully humid with hot summers (Köppen-Geiger classification Cfa; Kottek et al. 2006) and cold winters, sometimes experiencing frost. The mean annual temperature is 22.1°C but varies from a mean of 27.6°C in January to 17.6°C in July (climate-data.org). Mean annual rainfall is high at 1346 mm (climate-data.org) and peaks during April (175 mm) but is high even during the dry season (June to September) with August receiving the least (46 mm). The major aquatic habitats in the region include the Paraguay River (including the river's edge and rooted emergent meadows), large permanent wetlands or esteros (including shallow lakes and tropical peatlands), temporary grassy wetlands (including temporary pools, waterlogged short grasslands and flooded palm savannah) and temporary wooded wetlands (including temporary pools and flooded Chaco thicket) (Neiff, 2001). For the shallow lakes, extensive floating peatlands dominated by Cyperus giganteus typically border the shoreline. The departmental capital, Pilar, is situated on the left bank of the Paraguay at the confluence of the Arroyo Ñeembucú, which drains the Ñeembucú Wetlands. All field sites are located in central Ñeembucú, in the region adjacent the national highway (Ruta 4), as northern and southern areas of the department were inaccessible during much of the study period due to flooding. Sampling sites included the city of Pilar, the Regimiento de Caballeria N°2 Coronel Felipe Toledo (henceforth referred to as the 'Military Base'), which is a patch of natural habitat in Pilar and Estancia Santa Ana in the municipality of Guazu Cuá, well within the Ñeembucú Wetlands (see Figure 1). We used Quantum GIS 3.4.8 (QGIS Development Team, 2019) to create site maps.

Sampling design
We set up fifteen 100 × 10 m transects in or adjacent to all major habitats (see Table 1). We sampled each transect at least once per season between 26 April 2017 and 15 March 2019 during active flight periods (10:00-16:00, > 20°C and low wind speed). On each occasion we recorded the transect number, date, start and end times along with any changes in habitat noted since the We also noted behaviour as flying, resting, copulating or laying eggs. To maximise the number of species recorded, we further recorded all identifiable species that had evaded capture after each sampling event. Whenever we found interesting specimens outside of the sampling design, we opportunistically collected them, recording locality, time and habitat whenever possible. We identified all specimens to the lowest possible taxonomic level using identification keys, especially Louton (2006, 2010), Heckman (2006Heckman ( , 2008, Von Ellenrieder and Garrison (2007) and the literature relevant to each group. When necessary, we examined specimens under an AmScope SZMT2 stereomicroscope with AmScope MU1003 microscope camera. Wing venation terminology follows Riek and Kukalová-Peck (1984). Jeremy K Dickens made original drawings of morphological features important for species diagnosis, unless otherwise stated. For drawing adapted from other sources, we obtained permission from the copyright holder(s), as indicated in the figure legends.

Data analyses
We created a matrix of species incidence-frequencies per transect. From this, we estimated overall species richness with 95% lower and upper confidence limits determined by the bootstrap standard error method (100 repeats) and sample coverage using rarefaction-extrapolation in the iNEXT package (Hsieh, Ma, & Chao, 2016) run in R software (R Development Core Team, 2015). Relative abundance was defined categorically as Abundant, Common, Frequent, Occasional or Rare, according to the limits determined by dividing the linear species abundance curve (i.e. log of frequencies) into five equal parts and then back-transforming these to actual frequencies.
For each species, we tested for differences in occurrence frequencies by ecosystem (Ñeembucú Wetlands vs. Paraguay River), aquatic habitat, terrestrial habitat, season and behaviour (resting vs. flying) using chi-squared tests of independence. We used nonmetric multidimensional scaling (NMDS), based on Bray-Curtis dissimilarity indices between habitats calculated from species presence/absence per transect using the package vegan (Oksanen et al., 2013) to graphically depict the associations between species and habitats during spring-autumnsummer (henceforth SSA) and winter, separately, after removing uniques (species recorded only once) to reduce sampling bias.
We determined potential indicator species per wetland habitat type in SSA versus winter by calculating the association index between each species and habitat, for SSA or winter, using the R package indicspecies (De Cáceres & Jansen, 2016). The association index is the product of the specificity value, the probability of a surveyed site belonging to a certain habitat when the species is found in it, and the fidelity value, the probability of finding the species in sites belonging to each habitat (De Cáceres & Legendre, 2009;Dufrêne & Legendre, 1997). We used permutational tests to test the associations between species and habitat during SSA and winter.

Results
We recorded 60 species in Ñeembucú and estimated the actual total number of species in the sampling area to be between 62 and 90 species (Figure 2). Sample coverage was high (0.96), indicating near complete sampling. Abundance curves followed a logarithmic distribution [R 2 = 0.96 (SSA), 0.97 (winter)], demonstrating a lack of bias towards species abundance. The most frequently recorded species were Erythrodiplax paraguayensis (Förster, 1905), Ischnura fluviatilis Selys, 1876 and Miathyria marcella (Selys in Sagra, 1857) ( Figure 3a), with the addition of Erythemis peruviana (Rambur, 1842) and Erythrodiplax umbrata (Linnaeus, 1758) in SSA ( Figure 3b). A mix of species typical of different biogeographical regions were present and partitioned by habitat. Species endemic to the Chaco (and hence the Rio Paraguay basin) include Gynacantha convergens Förster, 1908, Orthemis philipi Von Ellenrieder, 2009, Oligoclada rubribasalis Von Ellenrieder & Garrison, 2008 and Aeolagrion philipi Tennessen, 2009. Most of these species were associated with wooded habitats, besides O. rubribasalis, which was exclusive to the river's edge. On the other hand, Erythrodiplax nigricans (Rambur, 1842), Tauriphila xiphea Ris, 1913 andLestes spatula Fraser, 1946 are typical of the Andes-Patagonia-Pampas subregion and found in more open grassland areas. Other species endemic to the Paraná-Paraguay basin include Aphylla distinguenda (Campion, 1920), which was associated with wooded thickets, including along the Paraguay River, and Edonis helena Needham, 1905, which was found exclusively in grassland. Species with localised distributions included Edonis helena, Erythemis carmelita Williamson, 1923 and Acanthagrion ascendens Calvert, 1909.  During SSA, we found eight potential indicator species per wetland type ( Table 2), five of which were associated with a single wetland type and three with two wetland types. Of these, the strongest associations were between Telebasis obsoleta (Selys, 1876) with large permanent and wooded temporary wetlands, Micrathyria tibialis Kirby, 1897 with wooded temporary wetlands and Micrathyria spuria (Selys, 1900) with large permanent and grassy temporary wetlands. Oligoclada rubribasalis and Perithemis mooma Kirby, 1889 are also strongly associated with the river, Acanthagrion ascendens and Micrathyria hypodidyma Calvert, 1906 to wooded temporary wetlands, and Orthemis nodiplaga Karsch, 1891 to large permanent and grassy temporary wetlands. We also recorded 14 species exclusive to a single wetland type: five to wooded temporary wetlands and three to each of the Paraguay River, large permanent wetlands, and grassy temporary wetlands (Table 3).
For winter, we found four potential indicator species (Table 2): Rhionaeschna bonariensis (Rambur, 1842) is associated with the Paraguay River, Micrathyria spuria and Tramea cophysa Hagen, 1867 with large permanent wetlands, and Telebasis willinki Fraser, 1948 with large permanent and wooded temporary wetlands. We also found six species exclusive to a single wetland Table 2. Potential indicator species (p < 0.1) per wetland type in central Ñeembucú based on occurrence frequency per site in spring-summer-autumn (SSA) vs. winter. The specificity value is the probability of a surveyed site belonging to a certain habitat when the species is found in it, and the fidelity value is the probability of finding the species in sites belonging to each habitat. The association index is the average between these values, as a measure of both fidelity and specificity. The p-value represents the results of permutational tests (999 permutations) of the association between species and wetland type.

Season
Specificity Fidelity type: two each to the large permanent wetlands and wooded temporary wetlands and one each to the Paraguay River and grassy temporary wetlands ( Table 3). The associations between species and habitats during SSA and winter are depicted in Figure 4, whilst a complete list of species associated with each wetland type, based on the indicator species analysis, is given in Table 3.

Checklist to the Odonata of central Ñeembucú
For the purposes of practicality of identification in the field, we provide descriptions of the most easily observed traits (i.e. colouration, size) for each species. However, colour is extremely variable and should be used with caution, so we have also included diagnostic morphological features for more accurate identification. Unless stated otherwise, we obtained information on species distributions and diagnostic traits from Garrison et al. (2006Garrison et al. ( , 2010, Heckman (2006Heckman ( , 2008 and Von Ellenrieder & Garrison (2007). An * indicates new records for Paraguay. Relative abundance reflects occurrence frequency, for SSA: Abundant ( > 28), Common (14 < x ≤ 28), Frequent (7.0 < x ≤ 14.0), Occasional (3.5 < x ≤ 7.0) and Rare ( ≤ 3.5), for winter: Abundant ( > 40), Common (25 < x ≤ 40), Frequent (15 < x ≤ 25), Occasional (10 < x ≤ 15) and Rare ( ≤ 10). For each species, environmental variables measured for all recorded specimens are given in Supplemental Information Appendix I, and occurrence frequencies per ecosystem, aquatic and terrestrial habitats, season and behaviour in Supplemental Information Appendix II, Table 4. A complete list of voucher specimens is provided in Supplemental Information Appendix III.
Lengths given for total length (TL), forewing (FW), hind wing (HW), pterostigma (PS) and abdomen (AB) in millimetres. VL = vulvar lamina of female and S1-S10 represent abdominal segments one to ten.   Figure 5a Rare Largest species in the region. General body colouration green with various dark brown or black markings. Face greenish yellow with black or brown triangle bordered by yellow on frons and often a small blue or brownish triangle on each side. In FW, upper sector of arculus shorter than lower sector and vein RP 2 with a marked convex bend at distal end of PS ( Figure 15g). HW of male lacks anal triangle and anal angle. HW: 45-52. AB: 47-55. Widely distributed in the Americas, typically found around lentic habitats. We only recorded a single individual flying above a flooded short-grassland near the Paraguay River in May.
Coryphaeschna adnexa (Hagen, 1861) Figure 5b-e Frequent (SSA), Occasional (winter) Face blue in male; mostly green, sometimes with blue, in female. Black T-spot on frons extends onto anterior surface and fills transverse groove on dorsal side. Thorax predominantly green with narrow brown lines along sutures, AB dark brown to black with green rings (narrow in male) (Tennessen, 2001;. Male epiproct less than half as long as cerci ( Figure 15i). Male -HW: 39-42. AD: 48-53. Female -HW: 41-45. AD: 52-57. Widespread in the Americas. In Ñeembucú, found in a variety of habitats. Generally recorded flying around 1-1.5 m above ground far from water in areas with relatively low mean vegetation height or along edge of wooded areas. Present year-round but more common in SSA, prefers high temperatures and sunny conditions.   Gynacantha convergens Förster, 1908 Figure 5l Rare Generally brown, brown-tinged wings to or slightly beyond first antenodal crossvein. In female, distance between lateral and ventral carinae on S3 at level of transverse carina narrowed to about half its width posterior to this point. S3 of male constricted at base. Female sternum of S10 with a sclerotised posterior process bearing two long apical spines ( Figure 15c). Anterior process of anterior hamule upturned and separated from base by a deep groove (Figure 15d Paraguay River ecosystem, occurring in a variety of habitats but especially along the river. Usually within 110 m of a water body in areas with dense terrestrial and/or aquatic macrophyte cover. Prefers cooler temperatures. Present late autumn and winter.

GOMPHIDAE
Aphylla distinguenda (Campion, 1920) Figure 6a, b Occasional AB gradually changing colour from dark brown below and light green above on anterior segments to reddish brown posteriorly. Thorax dark brown with two pairs of bold pale green lateral stripes and antehumeral stripes. Face mostly dark brown, frons with white to pale blue dorsal bar. Male cerci thick, bent sharply inward near middle and bear a strong tooth on inner surface proximal to bend ( Figure 16a). VL with V-shaped excision extending half of its length, base of excision rounded, angle between lobes 90°and lateral lobes broadly rounded ( Figure 16c) (Belle, 1992). HW: 33-35. AB: ca. 44. Restricted to Paraná-Paraguay basin. In Ñeembucú, found exclusively in wooded habitats (canopy 4-6 m) near the Paraguay River, particularly flooded Chaco thicket, where it can become common, but also observed in vegetated urban areas. Perches or patrols at ca. 1 m high over flooded ground, especially along thicket edges. Prefers high temperatures. Present summer and early autumn *Aphylla theodorina (Navás, 1933) Figure 6c, d Rare Adult male predominantly dark brown. Female and immature with abdominal segments pale yellow, S1-3 reddish brown dorsally, S4-7 with rings along transverse carinae and distal margins that are reddish-brown above and black below, posterior segments becoming entirely reddish brown. Thorax reddish brown, with three pairs of bold pale-yellow stripes laterally and two pairs dorsally, pale stripes along middorsal carina, anterior and posterior margins. Face mostly pale yellow with dark brown on antefrons, clypeus and vertex, anterior part of postclypeus mostly pale. Costal vein bright yellow. Male cerci with fringe of long black hairs along inner margin ( Figure 16b). VL with V-shaped excision for 1/2 to 3/5 its length, angle between lobes 60-90°and lobes broadly rounded ( Figure 16d) (Belle, 1992). HW: ca. 33. AD: 40-42. New country record. Widely distributed in South America (Bedê et al. 2015). In Ñeembucú, all three records were made over grassland areas in the Ñeembucú Wetlands during hot summer weather. In Ñeembucú, we made a single record at a temporary grassy pool after a period of heavy rains during autumn.

LIBELLULIDAE
Brachymesia herbida (Gundlach, 1889) Figure 7a, b Frequent Thorax yellow to dull green, AB yellow, S4-10 with black triangles extending from posterior margin to mid-point and black stripe extending further anterioly along middorsal carina.
Frons and vertex whitish with brown markings. Wings heavily stained with amber along anterior costal margin, central part and apex, veins dark brown. S1-3 greatly swollen in lateral view. Widely distributed throughout the Americas. In Ñeembucú, usually found along edge of the Paraguay River but also large lentic waterbodies in the Ñeembucú Wetlands. Hawks insects from a perch ca. 1 m off the ground within a few metres of the water's edge and generally with low vegetation (ca. 0.5 m) and/or bare ground (ca. 40%). Present summer and autumn.  Erythemis attala (Selys in Sagra, 1857) Figure 7i, j Occasional Body colour black with whitish dorsal markings on S7 (adult male) or greenish-brown with distal portion of S4-7 dark brown (female and immature). Lacks antehumeral stripes. AB shorter than HW, S4 slightly constricted in dorsal view, S1-3 moderately widened in lateral view. HW basal spot reaches cubito-anal crossvein and base of triangle, and covers a small basal region or marginal cells to anal angle (Rodríguez, Sarmiento, & González-Soriano, 2015). TL: 40-49. HW: 35-38 (male) and 32-35 (female). Widespread in Neotropics. In Ñeembucú, prefers wooded habitats (canopy 4-6 m, non-flooded) within ca. 60 m of water's edge, absent from grassy wetlands and urban areas. Perches ca. 1 m above ground. Present SSA. Williamson, 1923 Figure 7k, l Occasional Body colour scarlet to reddish-brown (adult male) or greenish-brown, with dark brown spots on S1-3, dorsal and lateral markings on S3-7 and covering dorsal and lateral surfaces on S8-10 (female) (Rodríguez et al., 2015;Williamson, 1923). Thorax lacks antehumeral stripes, legs mostly pale. AB shorter than HW, S4 notably constricted in dorsal view, S1-3 considerably widened in lateral view. Male -TL: ca. 47. HW: 33-35. New country record. Localised distribution across tropical South America. Recorded in the Ñeembucú Wetlands in or along the edge of wooded habitats with bromeliad undergrowth near lentic waterbodies, perches ca. 0.35 m above ground. Recorded during autumn.

*Erythemis credula (Hagen, 1861) Figure 7m-o Frequent
Body colour grey-blue to black (adult male) or ochraceous to brown with pale middorsal stripe extending across thorax to S3 and black antehumeral stripes (female and immature). AB with black middorsal stripe widening distally. AB shorter than HW, S4 slightly to moderately constricted in dorsal view, S1-3 moderately widened in lateral view. HW dark basal spot does not reach first antenodal crossvein but extends beyond cubito-anal crossvein ( Widespread in South America but new country record. In Ñeembucú, found exclusively around lentic waterbodies. Usually recorded close to or over water in areas with mixed terrestrial and aquatic vegetation cover with low height (often floating), perches ca. 25 cm above substrate. Present spring and summer.

Erythemis peruviana (Rambur 1842) Figure 7s-u Abundant
Adult male distinctly red from S4-10, rest of body dark metallic blue. Female and immatures body colour brown with pale yellow dorsal stripe from thorax to S3, dark antehumeral stripes; S3-10 pale dorsally, bordered by brown stipes with thin brown middorsal stripe and short dark brown horizontal stripes subterminal to S3-7. AB shorter than HW, dorsoventrally flattened, S4 not constricted in dorsal view, S1-3 moderately widened in lateral view. HW basal cloud small, not reaching first antenodal or anal angle vein (Rodríguez et al., 2015  Erythrodiplax media Borror, 1942 Figure 8a Occasional Adult male body colour blue-black, AB base with light blue pruinescence up to S7. Adult female with brownish black or bluish black face, thorax pale brown to reddish brown. Immature yellow with dark brown markings on AB. HW with prominent dark brown to black (males) or amber (female) basal spot, reaching first antenodal crossvein and almost reaching triangle. FW triangle crossed. Viewed laterally, lateral lobes of vesica spermalis not more than one third as wide as apex of terminal segment; median process extends beyond apex of median lobes by a distance equal or greater than length of lateral lobes and not bilobed ( Figure 19i). VL generally more or less rounded in lateral view with base less than half as wide as its length, shorter than S9 and convex dorsoposterior margin ( Figure 19n). TL: 26-32. HW: 21-26 (male) and 19-24 (female) (Borror, 1942) . Distributed between Bolivia, Paraguay, N Argentina and SE Brazil. Recorded twice, exclusively along the Paraguay River, in wooded patches with shade, 5-10 m from the water's edge, 0.5 m above the ground, at very high temperatures. Present SSA.

Erythrodiplax nigricans (Rambur, 1842) Figure 8b-e Common
Body colour black with pale patch on S7, dark reddish-brown thorax and metallic blue frons and vertex (adult male) or olive green to yellow, black lateral markings on S4-10, reddish-brown markings and black dorsal stripe on S8-10, AB white ventrally, thorax darker brown dorsally with pale middorsal stripe (female and immature). Cerci white. HW with a small orange brown basal spot, barely visible in males. PS brown with distinct dark anterior and posterior borders; mature specimens with faint orange-brown area posterior to PS. FW with at most 8½ antenodal crossveins, triangle and subtriangle crossed, radial planate with one row of cells, apical planate changing from one to two rows of cells distally (Figure 18j). Penultimate spine at outer angle of hind femur 1/3 length of ultimate spine or less (beware of broken spines!). In lateral view, inner branch of hamule bent rather abruptly caudad often obscuring the inner branch ( Figure 19e). Median process of vesica spermalis extends slightly or not at all beyond apex of median lobes and lacks tuft of bristles at its tip, posterior lobe well developed (Figure 19j). In lateral view, VL shorter than S9, generally rounded and more than half as wide at base than long ( Figure 19o) (Borror, 1942;Garrison et al., 2006  Restricted to Pampas biome. More common in the Paraguay River ecosystem than the Ñeembucú Wetlands. Prefers open habitats, including grassy temporary wetlands and emergent meadows, with high vegetation cover but low height ( < 0.5 m). Forages ca. 10 cm above the ground, usually within ca. 30 m of water's edge. Present in urban areas. Prefers mild to hot temperatures. Present SSA, abundance peaks in autumn. Distal segment of vesica spermalis long and cylindrical, with complex and largely hidden distal lobes, gradually widening to rounded or bluntly angulated tip (Figure 19k). In lateral view, VL triangular with nearly straight sides and pointed apex (Figure 19p). In female, posterior lobe of prothorax quadratic and not narrowed distally, and penultimate spine at outer angle of hind femur at least 1/3 the length of ultimate spine. HW: 20-22. Widespread in Neotropics. In Ñeembucú, found in all habitats, usually with high vegetation cover of moderate height, and within ca. 30 m from the water's edge. Perches ca. 0.3 m above substrate. Prefers warm temperatures. Present year-round.

Erythrodiplax ochracea
Erythrodiplax paraguayensis (Förster, 1905) Figure 8j-n Abundant In adult male, AB light blue and pruinose with black tip, thorax blackish, frons and vertex metallic blue. Female and immature predominantly yellow to brown with dark antehumeral stripes and dorsal and posterolateral markings on AB segments (Borror, 1942). Wings hyaline, sometimes with small black basal spot on HW (Figure 17m), PS light grey with dark borders. FW triangle usually free. In lateral view, lateral lobes of vesica spermalis at least half as wide at base as at apex of terminal segment; median process extends beyond apex of median lobes to a distance at least equal to length of lateral lobes and not bilobed (Figure 19 l). Female cerci convex at tip, VL more or less rounded in lateral view (Figure 19q

Erythrodiplax umbrata (Linnaeus, 1758) Figure 8o-r Abundant
Wings with distinctive black bands (adult male and homochromatic female) and/or tinged with brown, especially at apex. Body colour variable from yellow to reddish-brown, AB with black middorsal stripe and black patches on distal portion of S4-9, S10 black, thorax with dark humeral stripes. Cerci pale. Rspl with two rows of cells, Mspl with one row of more than six cells, radial planate absent. FW with at least 9½ antenodal crossveins, triangle and subtriangle crossed, vein MP of HW arises at anal angle of triangle ( Figure 18i). Larger than other Erythrodiplax in the region. HW: 26-34. AB: 22-32 (Borror, 1942). Widespread in the Americas. More prevalent near the Paraguay River than in the Ñeembucú Wetlands but found in all habitats, preferring areas with relatively high terrestrial vegetation cover and moderate height, sometimes far from water, usually ca. 0.5 m above ground. Tolerates mild to high temperatures. Present SSA.  (Figure 19ac) (May, 1998). VL not projected ventrally (Figure 19ad).     Orthemis discolor (Burmeister, 1839) Figure 10g Occasional Adult male violet. Female and immature brown with two pale longitudinal stripes on pterothorax. Wing veins black and membrane surrounding nodus hyaline. Widespread in tropical South America. Although no individuals were collected, we observed several violet coloured Orthemis males that we tentatively identified as this species at large permanent wetlands, temporary grassy wetlands and flooded palm savannah, during autumn.  & Muzón, 1999). Widespread in Neotropics. Strongly associated with the Paraguay River but also found at nearby grassy temporary wetlands. Usually perched around 0.7 m but up to 2 m above substrate at water's edge in low to moderately high riparian vegetation. Cool to relatively high temperatures. Present SSA.

Orthemis nodiplaga
Tauriphila argo (Hagen, 1869) Figure 10s-v Frequent S4-10 red, rest of body dark brown to black and pruinose (male) or body mostly orange to yellowish-brown with thin black middorsal stripe from S4-7 (female and immature). Face red to reddish-brown, metallic violet postfrons and vertex in mature specimen. HW very broad at base with dark basal patches extending to anal angle and continuing along vein margins, or extensive amber wash in some females. HW: 34-39. AB: 25-32. Widespread in Neotropics. Recorded at large wetland types, absent from temporary pools, generally flying around 1-3 m above adjacent terrestrial habitat, especially forest/thicket edge, sometimes far from water's edge. Prefers high temperatures. Present SSA, abundance peaks in autumn. Tramea cophysa Hagen, 1867 Figure 10ac-af Common Body colour brown, thorax with two lateral oblique pale stripes, S9-10 mostly black. Postfrons metallic violet-blue (male) or pale yellow with posterior metallic violet-blue stripe (female) (Marmels & Rácenis, 1982). HW very broad at base with dark brown to black basal spot reaching no further than vein MP. Medial, radial and apical planates with two cells, PS short. HW: 39-44. AB: ca. 31. Widespread in Neotropics. Recorded at all large wetland habitat types, absent from small temporary pools, becoming associated with large permanent wetlands during drier periods. Found flying or perched around 1 m above substrate, generally within 20 m from water's edge, over sunny areas with variable vegetation cover and low to moderate height. Tolerates mild to relatively high temperatures. Present year-round, peak abundance during autumn.

ZYGOPTERA CALOPTERYGIDAE
Hetaerina rosea Selys, 1853 Figure 11a, b Occasional Male FW with bright red basal spot, HW base dark reddish-brown with additional red spot at tip; thorax and base of AB coppery, AB black distally. Female body colour reddish-brown, wings amber, without red spots. Wings not petiolate, ca. 21 antenodal crossveins and mid-basal space subdivided by crossveins (Figure 20a). In male, length of median lobe and distal 1/3 of cerci approximately equal, paraprocts longer than ½ of cerci. Female with well-developed occipital tubercles and posterior lobe of prothorax with angled sides. TL: 37-50. HW: 25-30. AB: 36-37 (male) and 31-32 (female). Widespread from Peru to northern Argentina. In Ñeembucú, recorded in wooded habitat bordering streams and in the Paraguay River ecosystem, including in urban settings. Recorded late winter and spring. Calvert, 1909 Figure 11c, d Occasional Male body colour typically light blue to green and black, S1-7 black dorsally (sometimes almost entirely black), S8-9 entirely pale, S10 black with pale venter; thorax pale with black humeral and middorsal stripe and pale antehumeral stripes; head black posterior to frons with large pale postocular spots, blue anteriorly. Female colouration similar but tinged brown and dark areas less extensive, S8 similar to S1-7, S9 blue with black on basal half of lateral portion, S10 entirely blue. In male, S10 dorsally elevated, cerci long (1.2-1.4 mm), ventrally inclined and subapically constricted (Figure 21k). Mesepisternal fossae separated from posterior end of sinus by more than twice their own length, their long axis parallel to middorsal carina; middorsal carina persistent between fossae and posterior end of interlaminal sinus ( Figure 22f) (Leonard, 1977;Souza, Costa, & Santos, 2010). . Locally distributed in tropics to the north and south of Amazonia (Leonard, 1977). In Ñeembucú, recorded exclusively at wooded temporary wetlands, including flooded palm savannah. Always found over water, usually at height of ca. 0.5 m. Vegetation cover usually moderate to low with mixture of terrestrial (ca. 40%) and aquatic (ca. 20%) species but up to 5 m tall (i.e. Copernica alba palms), with ca. 60% shade and cool to mild temperatures. Only males recorded. Present SSA.

Acanthagrion lancea Selys, 1876 Figure 11e-h Frequent
Body colour similar to A. ascendens but, in male, blue lateral markings on S7 form elongated triangle; in female, S8 with joined dorsal and lateral black stripes and S9 with bilobate anterior black mark. In male, S10 not elevated, cerci slightly downwards inclined, rounded at tip in lateral view, constricted subbasally and subapically, paraproct sharply recurved at tip (Figure 21 l). Mesepisternal fossae adjoining mesepisternal sinus, rounded or elliptical in shape, their long axis transverse to middorsal carina. Posterolateral margins of sinus smoothly convex, interlaminal sinus entire ( Figure 22d) (Leonard, 1977;Souza et al., 2010). HW: 15-18. AB: 23-26. Disjunct distribution in SE Brazil-Paraguay-Argentina, and Peru-Ecuador. Recorded in a variety of habitats, generally above or close to water, at 0.2 m height, in areas with variable terrestrial vegetation cover and height and variable aquatic vegetation cover but low height, low shade and at mild temperatures. Present year-round, peak abundance in autumn, scarce during spring and summer.
*Acanthagrion temporale Selys, 1876 Figure 11i-j Rare Adult male with more extensive pale (light blue to green) colouration than other Acanthagrion species; S3-7 with narrow black dorsal stripes, expanded posteriorly, S8-9 entirely pale; head mostly black, posterior of frons with two pale ovoid postocular spots connected by a bar, anterior to frons mostly blue but postclypeus black. Female colouration similar. In male, S10 not elevated, cerci constricted subapically, in lateral view. In female, mesostigmal laminae diagonally traversed by a strong fold; subtriangular area between this and admesal borders of lamina subplanate; mesepisternal fossae separated on midline, elliptical in shape with pointed end directed laterally, margin at this point indistinct, merging with mesepisternal surface (Figure 22e) (Leonard, 1977 Tennessen, 2009 Figure 11k-n Rare Body colour mostly tan brown, black dorsally with two pale blue antehumeral stripes on thorax. Rear of head usually pale above occipital foramen, sometimes with oblong postocular spots, and a narrow lateral black bar along edge of compound eyes. In male, S8-9, venter of S10, postclypeus, gena and labrum pale blue, top of head variably brown to black. Male cerci, in lateral view, ca. 1.5 times longer than S10, wider at apex than base (apical width about 2/3 of cerci length) (Figure 21c). Female mesanapleural suture with marked dorsal convexity and black spot below (Figure 22a). Male -HW: 14-16. AB: 22-25. Female -HW: 15-17. AB: 21-25 (Tennessen, 2009). New country record. Chaco endemic distributed from S Bolivia to N Argentina. Only recorded in gallery forest interior (with extensive bromeliad undergrowth) in the Ñeembucú Wetlands during winter.

*Aeolagrion philipi
Argentagrion ambiguum (Ris, 1904) Figure 11o-r Common Male and andromorphic female body colour light blue or green and black; S1-8 dorsally black, S9-10 mostly pale; thorax laterally pale, dorsally black with pale antehumeral stripes; head dorsally black with elongated postocular spots, anteriorly mostly pale but labrum and postclypeus distinctly black. Heteromorphic female mostly pale brown; AB black dorsally, S9-10 mostly pale blue; thorax with thin pale blue to green antehumeral stripes; head (including labrum and entire back of head) brown. In both sexes, posterior lobe of prothorax widely bilobate (Figures 21s,22i) and PS rhomboidal with costal side the longest (Figure 21v) . Male cerci, in dorsal view, about twice as long as wide, margin of S10 entire ( Figure 21o); in lateral view, dorsal branch of paraprocts rounded (Figure 21p). In female, lateral margins of mesostigmal plates bluntly pointed. HW: 13-18. AB: 18-22. Distributed across south-eastern South America as far north as SE Bolivia. Recorded in a variety of more open habitats, absent from wooded temporary wetlands. Usually found close to water, in grassy vegetation with high cover and low height and low aquatic vegetation cover, around 20 cm above substrate, at cool to hot temperatures. Present year-round, abundance peaks during autumn and winter.

Homeoura lindneri Ris, 1928 Figure 11s-x Common
Male and andromorphic female black with pale blue to yellow and black; S1-7 black dorsally, S8-9 entirely pale, S10 pale with black posterior margin; thorax pale laterally, dorsally black with pale antehumeral stripes; head dorsally black with large oval pale postocular spots, postocular bar present, sometimes fused to spots. Heteromorphic female similar to male but dark colouration includes brown, especially along humeral stripes, S9 with dark dorsal marking, and entire back of head pale. PS rhomboidal (Figure 21w). In male, posterior margin of S10 with U-shaped cleft and two apical tubercles (Figure 21q), cerci about as long as or shorter than S10, in lateral view, dorsal and ventral margins diverging apically and dorsal margin longer than ventral, such that apex is wider than base, apex obliquely truncated dorsoventrally ( Figure 21r); medial projection of posterior lobe of prothorax approximately rhomboidal (Figure 21t). In female, medial projection of posterior lobe of prothorax triangular to rectangular, and lateral margins of mesostigmal plates bluntly pointed (Figure 22j). FW: ca. 14. AB: 20-21 . Disjunct distribution in La Plata basin and Peruvian Amazon. Recorded in all habitats but with a preference for the margin of the Paraguay River. Usually found over drier areas than most other species (besides T. willinki) but still mostly within 10 m of water, vegetation cover relatively high and mean height low, but with some taller trees, aquatic vegetation variable. Perches ca. 20 cm above substrate. Tolerates cool to hot temperatures. Present year-round, less prevalent during summer.

Homeoura nepos (Selys, 1876) Figure 11y-aa Frequent
Male body colour pale blue to yellow and black; S1-8 and S10 black dorsally, S9 mostly pale with black anterior margin; thorax laterally pale, dorsally black with pale antehumeral stripes; head dorsally black with large pale postocular spots, sometimes with a concave anterior margin, and postocular bar present. Female colouration generally browner; dorsally black from S1-9, S10 mostly to entirely pale, heteromorphic female with entire back of head pale. In both sexes, medial projection of posterior lobe of prothorax approximately rectangular (Figures 21u, 22k) and PS quadrangular (Figure 21x). In female, lateral margins of mesostigmal plates bluntly rounded, anterior and posterior margins approximately parallel sided (Figure 22k) Figure 12a-e Frequent Very small. Body colour mostly light blue or green with black; AB black dorsally from S1 to basal half of S9, S9 entirely pale blue, S10 black dorsally; head dorsally black with small rounded pale postocular spots, pale anteriorly, except for black postclypeus. Thorax of male and andromorphic female dorsally black with pale antehumeral stripes but distinctly bright lime green thorax with black middorsal stripe in heteromorphic female (Figure 12b, c). In male, posterior margin of S10 raised and deeply forked, cerci entire and paraprocts forked and at least as long as S10 (Figure 21n). In female, posterior lobe of prothorax with a medial cleft and mesostigmal plates separated (Figure 22 g). HW: [8][9][10][11][12][13][14][15][16]. Widespread in Neotropics. More prevalent in the Ñeembucú Wetlands than the Paraguay River ecosystem and found in all lentic wetland types. Usually found just above water ( < 20 cm) in areas with high water cover (ca. 70%), moderate to high terrestrial vegetation cover with low mean height and substantial (ca. 25%) low-growing aquatic vegetation (ca. 0.2 m tall). Low to high temperatures. Present year-round, peak abundance in winter.

Ischnura fluviatilis Selys, 1876 Figure 12f-n Abundant
Male and andromorphic female body colour pale blue to green and black; S1-7 and S10 dorsally black, S8-9 pale blue with black along dorsoanterior edge; thorax dorsally black with pale antehumeral stripes; head dorsally black with small rounded pale postocular spots, anteriorly pale with black postclypeus. Body colour of heteromorphic females highly variable with blue, green, brown and/or orange and black, individuals with an orange thorax distinct in region; AB segments black dorsally; postocular spots sometimes fused into wide postocular bar. In male, posterior edge of S10 entire, not raised; cerci bifid with subequal branches; paraprocts entire, curving dorsally with a pointed tip directed distally, shorter than S10 (Figure 21 m). In female, posterior lobe of prothorax bilobate, mesostigmal plates confluent, forming a single rhomboidal structure (Figure 22 h) (Lencioni, 2006;Realpe, 2010). TL: 28-36. HW: 14-18. Widespread in South America. Recorded in all habitats but prefers open areas, especially grassy temporary wetlands, emergent meadows and large permanent wetlands, scarce in wooded wetlands. Usually close to water, ca. 20 cm above substrate, in areas with moderate to high low-growing terrestrial vegetation cover, variable (generally lower) aquatic vegetation cover. Tolerates low to high temperatures. Present year-round, less abundant during summer.

Telebasis obsoleta (Selys, 1876) Figure 12o-t Common (SSA), Occasional (winter)
Both sexes lack humeral stripes and have distinctly pale eyes. Body colour almost entirely light blue or olive green in males and light brown in females, black restricted to middorsal thoracic stripe and on dorsum and posterior margins of S2-7 (reduced to submarginal posterodorsal patches in some females) and S10 in male. Male cerci in dorsal view, approximate with distance between them less than 0.2 their basal width (Figure 21d, e), in lateral view, a strongly elevated dorsally directed medial ridge is clearly visible, posterodistal margin acuminate (Figure 21d, e). Female middorsal carina well developed along anterior portion, separating a pair of large mesepisternal pits (ca. twice as long as wide) and posterior lobe of pterothorax broadly bluntly angulate laterally (Figure 22b) (Garrison, 2009). HW: ca. 17. AB: 27-28. Widespread in humid tropical South America. Associated with large permanent wetlands and wooded temporary wetlands in the Ñeembucú Wetlands, but also in flooded grassland and the Paraguay Rive ecosystem, including wooded suburban areas. Usually in areas with moderately low terrestrial veg cover (ca. 45%), but tall canopy (ca. 3-5 m) and partial shade (ca. 50%), ca. 15 cm above substrate. Low to high temperatures. Present year-round.

Telebasis willinki Fraser, 1948 Figure 12u-x Common
Very small, mostly red coloured damselfly with bronzy pterothorax. Male cerci in dorsal view, divergent and distance between bases of cerci more than half of basal width of each cercus, in lateral view, subequal in length to paraprocts and distal half straight (Figure 21f, g). Female mesepisternal sinus modified into a 'cup-like' formation with posterior margin of mesostigmal plate strongly raised (Figure 22c) (Garrison, 2009). TL: 23-29. HW: 12-14. Widespread in humid tropical South America. Associated with large permanent wetlands and wooded temporary woodlands in the Ñeembucú Wetlands, but also in forest and along the Paraguay River, uncommon in grassy wetlands unlike in the Argentine Yungas (Von Ellenrieder & Garrison, 2007). Usually ca. 0.5 m above substrate, generally close to water (but far in forest interior) in areas with high terrestrial vegetation cover, relatively low mean height and moderate to high maximum height, variable shade. Prefers mild to high temperatures. Present year-round, peak abundance in winter.

LESTIDAE *Lestes minutus Selys, 1862 Figure 13a-f Occasional
Adult male AB mostly black with pale blue to tan lateral markings on S1-7, thorax dorsally black with pale middorsal and humeral stripes, laterally blue and pruinose, black along dorsal margin of mesepimeron, head and eyes mostly black with labrum, anterior margin of anteclypeus and gena pale. Female and immature mostly light brown, entire face and eyes light grey to blue. In both sexes, venter of thorax with three large dark marks and one small brown spot on each side (Figure 20d). Male cerci bear two strong teeth on inner surface, one at base and the other proximal to apex with a row of teeth located between them (Figure 20f). Male -HW: 16-19. AB: 26-30. Female -HW: 18-20. AB: 25-28. New country record, representing a 1000 km southward range expansion from previous limit in Mato Grosso. Widespread in temporary grassland wetlands in South America. Recorded at grassy temporary wetlands and large permanent wetlands. Usually in areas with high water cover (ca. 80%), and variable short (grassy) vegetation cover, ca. 10 cm above substrate. Low to high temperatures. Present autumn, winter and spring, peak abundance during winter.

Lestes spatula Fraser, 1946 Figure 13g-j Rare
Adult male S1-6 dorsally metallic black, laterally pale blue, S9-10 mostly pruinose pale grey, S7-8 transitional, thorax dorsally pale blue with metallic postdorsal stripes, head dorsally black, anteriorly pale blue, eyes vivid blue. Female and immature body colouration similarly patterned to male but pale areas greenish to bluish brown, S7-10 similarly patterned to anterior segments, mesepimeron with thin metallic longitudinal stripe, eyes blue to grey. In both sexes, venter of thorax with two tiny black dots on anterior portion and two diffuse brown stripes (Figure 20e). In lateral view, cerci appear straight and have only a basal tooth on inner margin, narrowed along distal ¼ and about as long as paraprocts (

Aeshnidae
3 Body colour plain brown ( Figure 5 l), wings brown-tinged to first antenodal crossvein or slightly beyond. Proximal cell of each discoidal triangle crossed; anal triangle two celled. (Figure 15a). In female, sternum of S10 with a sclerotised posterior process bearing two long apical spines (Figure 15b)  3' Body colour includes red, green, blue and/or black (not plain brown); wings not brown tinged to first antenodal or slightly beyond. Proximal cell of each discoidal triangle not crossed (Figure 15c) (Figure 5c, k), wing veins black (Figure 5b, j) ....7 Figure 15. Key diagnostic features of Aeshnidae species in Ñeembucú: (a) proximal cell of each discoidal triangle crossed and anal triangle two celled in Gynacantha convergens versus, (b) proximal cell of each discoidal triangle not crossed and anal triangle one celled; (c) female sternum of S10 with a sclerotised posterior process bearing two long apical spines in Gynacantha; (d) anterior process of anterior hamule upturned and separated from base by a deep groove in Gynacantha; male sternum of S1, in lateral view (e) with conical tubercle in Rhionaeschna, versus (f) without conical tubercle; (g) vein RP 2 has a marked convex bend at distal end of PS and upper sector of arculus shorter than lower in Anax amazili, versus (h) RP 2 curves evenly at distal end of PS and upper sector of arculus as long or longer than lower sector; epiproct reaches (i) ca. 40% of cerci length in    44 Basal spot covers small basal region or row of marginal cells. Legs dark or pale only on distal portion of upper half. Body colour black with whitish marks on S7 or greenishbrown with dark brown distal portion on S4-7. S1-3 moderately widened (Figure 7i, j) Erythemis attala 44' Basal spot covers penultimate or marginal rows of cells. Legs pale. Body colour scarlet to reddish-brown or greenish-brown with dark brown dorsal and lateral markings on S3-7. S1-3 considerably widened (Figure 7k, l)  (h) small and round in male Ischnura, (i) small and elongate with postocular bar, or (j) large, ovoid and connected by postocular bar; male S10 and anal appendages, in lateral view, of (k) Acanthagrion ascendens, and (l) Acanthagrion lancea; mediodorsal view of S10 and anal appendages of (m) Ischnura fluviatilis and (n) Ischnura capreolus; dorsal and lateral views of male S10 and anal appendages of (o, p) Argentagrion ambiguum and (q, r) Homeoura lindneri; shape of male pronotum in (s) Argentagrion ambiguum; (t) Homeoura lindneri, and (u) Homeoura nepos; HW pterostigma shape in ( Figure 22. Key diagnostic features of Coenagrionidae species in Ñeembucú, part two, females: (a) mesanapleural suture with marked dorsal convexity and black mark below in Aelagrion philipi; pronotum and mesostigmal plates of (b) Telebasis obsoleta and (c) Telebasis willinki; mesostigmal plates of (d) Acanthagrion lancea, (e) Acanthagrion temporale, and (f) Acanthagrion ascendens; and pronotum (above) and mesostigmal plates (below) of (g) Ischnura capreolus, 14 PS approximately quadrangular, with costal side the shortest (Figure 21x)

Discussion
The 60 species recorded in Ñeembucú represent 33% of species known from Paraguay, whilst 11 (18%) were new country records, raising the total number of species known from the country from 133 (Paulson, 2004) to 141. This suggests that the total number of species listed for the country is substantially underestimated. In fact, the proportion of species that are new records is similar to that found during a study on butterflies in Paraguay (Dickens, McMahon, & Binnie, 2019), which estimated that up to half the species present in the country had not yet been recorded. Whether the degree of underestimation is as large for the Odonata is unclear. However, the country total is around half that of the neighbouring states of Brazil (Bedê et al., 2015) and Argentina (Von Ellenrieder & Muzón, 2008), which share the same bioregions, and suggest that it is indeed substantial. Furthermore, the species list for Ñeembucú is clearly also incomplete with much of the department remaining unsurveyed, whilst some of the larger and faster flying species may have evaded capture. Therefore, sampling in previously unsurveyed areas, especially along streams, and the use of different collection techniques would likely increase the number of species recorded. Nevertheless, the recorded species richness and composition for Ñeembucú are similar to the Eastern portion of the Argentine Chaco, which has 53 recorded species . This is unsurprising given its geographic proximity, although it covers a larger area. The recorded species richness is also only slightly lower than for the world-renowned Iberá Wetlands, 100 km to the south in Corrientes, Argentina, with 75 recorded species , although this was recorded over a longer period (six years) and falls within the range of the total number of species estimated to occur in Ñeembucú. However, the species composition in Ñeembucú is notably different to that of Iberá , despite the fact that they both fall within the correntino complex of the Chaco biome (The Nature Conservancy et al., 2005). The similar physiognomies, limnology and climate Poi de Neiff, 2003) between these regions rules them out as potential drivers. Rather, it suggests that they are the result of different biogeographical histories (centres of endemism and river basins). In this case, the Odonata of the Ñeembucú Wetlands clearly have a close affinity to the Chaco biome, although elements from the Andes-Patagonia-Pampas subregion and the Paraná River basin are present. On the other hand, the Odonata of the Iberá Wetlands have a strong affinity to the Paraná River basin , even though the terrestrial plant communities are Chacoan. Similar cases of Odonata compositional differences between nearby sites with similar environmental conditions across biogeographical boundaries are well documented elsewhere in South America (Brasil, Vieira, De Oliveira-Junior, Dias-Silva, & Juen, 2017;Juen, Cabette, & De Marco, 2007;Juen & De Marco, 2012). Therefore, patterns of Odonata diversity across South America are best understood in a historical biogeographical framework, although the exact positions of the boundaries between biogeographical regions are unclear because they are influenced by both terrestrial and freshwater ecoregions and require further investigation.
Furthermore, the partitioning of species from different biogeographical regions in different habitats in Ñeembucú is highly characteristic of a regional ecotone since the local distribution of species is constrained by their interactions with keystone environmental structures (vegetation, aquatic habitat and microclimate) and other species (Gosz, 1993;Kirkman, Drew, West, & Blood, 1998;Risser, 1995;Tews et al., 2004). Von Ellenrieder (2000) observed similar trends in the subtropical forest-pampas ecotone in Buenos Aires with subtropical species (including Telebasis willinki) restricted to the forest and Lestes species and other temperate species to the grasslands. The resultant blend of species is responsible for the elevated levels of species richness so characteristic of such ecotones (Brothers, 1993;Carter, Gammon, & Garrett, 1994;Risser, 1995;Shmida & Wilson, 1985;Wolf, 1993).
In terms of the selection of indicator species, several species are strongly associated with wetland types, making them reliable indictors of these habitats. Von Ellenrieder (2010) conducted a similar indicator species analysis for wetlands of the Argentine Humid Chaco but the species selected are some of the most common and widespread species in Ñeembucú. This is testament to the massive extent and good health of wetlands in the Ñeembucú and includes E. peruviana, E. ochracea, E. paraguayensis and to a lesser extent A. ambiguum, E. umbrata, and M. longifasciata for marshes and T. willinki, M. marcella, and to a lesser extent D. intensa, E. plebeja and P. mooma for large permanent lentic waterbodies. In this study, however, we found T. willinki to be more specifically associated with large permanent wetlands and nearby temporary wooded wetlands (in winter), whilst P. mooma had a strong association with the Paraguay River and nearby temporary grassy wetlands. Unfortunately, sample sizes were too small for D. intensa and E. plebeja to be considered potential indicator species. However, D. intensa had a strong fidelity to the river but was also recorded at large permanent wetlands, temporary wooded wetlands and along the forest edge. E. plebeja, on the other hand, had a strong association with large permanent wetlands and wooded temporary wetlands. Further sampling is required across more sites to confirm the association of these more weakly associated species to wetland types.
The unique diversity of the Ñeembucú Wetlands indicates their high conservation potential. Previous attempts to identify priority areas for biodiversity conservation in the Chaco biome have consistently earmarked the Ñeembucú region (Nori, Torres, Lescano, Cordier, Periago, & Baldo, 2016;The Nature Conservancy et al., 2005) but this has been restricted to the use of vertebrate groups and ecosystems. This study offers the first evidence of their importance for the conservation of invertebrates. This is particularly true for species endemic or near endemic to the Chaco and Pampas biomes and/or the Paraná and/or Paraguay River basins and those with localised distributions. Additionally, the large permanent wetlands, in particular, appear to play a critical role in maintaining the regional diversity by acting as refugia during dry periods for species also associated with temporary wetlands. Although we found species associated with temporary habitats in combination with large permanent wetlands (Table 2 and 3), this survey was carried out entirely within a wet cycle (La Niña). However, in dry periods (El Niño), most these temporary habitats will dry up completely, leaving only the perimeter of large permanent wetlands as habitat for these species. Even within this study, species associated with temporary wetlands became largely restricted to the large permanent wetlands during the dry season. This was most evident in M. spuria and L. minutus.
In order to prevent any further degradation and improve the current environmental condition of the Ñeembucú Wetlands, we recommend the following actions: (1) preventing wetland drainage and (2) restoring previously drained sites; (3) implementing environmentally sound road building practices, especially with regards to alterations to water flow; (4) implementing of controlled grazing practices; (5) enforcing national regulations surrounding agrochemical usage; (6) raising awareness about the importance of wetlands; (7) fostering stewardship of local landowners and (8) promoting Odonata as a flagship group for the protection of wetlands, especially by (9) highlighting their crucial role in public health by reducing the prevalence of mosquito-borne diseases, such as dengue (Saha, Aditya, Banerjee, & Saha, 2012;Shaalan & Canyon, 2009).