Review of the “metallic group” of species of Argia Rambur known from Venezuela, with description of the larva of Argia jocosa Hagen in Selys, 1865 (Odonata: Coenagrionidae)

In Venezuela, the “metallic group” includes three species: Argia cupraurea Calvert, Argia jocosa Hagen in Selys, and Argia orichalcea Hagen in Selys. These are here diagnosed and illustrated, and their distribution in Venezuela is mapped. The larva of A. jocosa differs from the few other known larvae of the group in details of the prementum, labial palp and shape of caudal gills.


Introduction
The genus Argia Rambur, 1842, includes about 112 valid species (Garrison et al., 2010), plus two or three dozen of mostly South American species that still await description. At least 13 of these (R.W. Garrison personal communication, January 2012) fall into the "metallic group" of species in which the males show brilliant metallic reflections on top of head, thoracic dorsum and mesepimeron, and dorsally bright red compound eyes. In the females the metallic areas are restricted to parts of the head, mid-dorsal and humeral stripes. Three species of the "metallic group" have been recorded from Venezuela, this country being the type locality of one of them: Argia orichalcea Hagen in Selys, 1865. The other two species are Argia cupraurea Calvert, 1902, and Argia jocosa Hagen in Selys, 1865. However, even though the presence in Venezuela of these two is confirmed in the present study, most records published so far are actually based on misidentified specimens. Venezuelan males of either species do not key out easily in Calvert's (1901Calvert's ( , 1909 keys, because in specimens of A. cupraurea abdominal segment 7 is not "black with a basal blue ring" (Calvert, 1901: 71;1909: 120), but blue with only the apical fifth or less black. Venezuelan males of A. jocosa have abdominal segments 3-5 blue for two-thirds or more of their length, and segment 6 is blue in its basal three-fifths, while Calvert (1901: 71;1909: 120) describes *Email: demarmjc@gmail.com ISSN 1388-7890 print/ISSN 2159-6719 online segments 3-6 as blue in their "basal half". As a result of this confusion, all specimens of A. jocosa in the Museo del Instituto de Zoología Agrícola "Francisco Fernández Yépez" (MIZA) collection were identified in the past by J. Rácenis and by myself as "Argia cupraurea", while those of true A. cupraurea were set apart as belonging to a probably undescribed species. The heretofore only Venezuelan record of A. jocosa (De Marmels, 1990) in fact refers to a misidentified A. orichalcea. Besides the description by Geijskes (1946) of a probable F-2 larva of A. orichalcea, the larvae of the three species are unknown. Here I describe an exuvia of a reared female of A. jocosa. Thanks to correspondence with Rosser Garrison, and some unpublished manuscript notes and figures he kindly furnished me with, the identity and distribution of all three metallic species in Venezuela can finally be presented.

Material and methods
All male and female specimens of the three metallic species of Argia stored at MIZA, as well as published and unpublished records of specimens identified in the past, now housed at other institutions, were examined. Colour illustrations were executed with poster paint (guache) from colour slides of live Venezuelan specimens. The greyish blue violaceous colour of live male A. orichalcea was found to be too pinkish in the original painting, and hence was modified with the Extended edition of Adobe Photoshop (CS5) for the present illustration. Line drawings were made with the help of a camera lucida coupled to a Wild M-8 stereoscope. Maps were generated with gvSIG 1.11.0 (Asociación gvSIG, 2011). A few distributional records forwarded by R.W. Garrison (RWG) were incorporated. Measurements (n = 10 adults of each sex) are given in millimetres. S1(-n) stands for abdominal segments 1-n. Calvert, 1902 (Figures 1-10, 13) Type locality: PANAMA: David

Diagnosis
Male (live colour Figure 1a). Labrum violet metallic, except for narrow orange border. Live specimens with top of head and thoracic dorsum amethyst violet metallic, not coppery red. Small, blue spot near upper end of humeral suture on mesepimeron of male normally present. S7 blue above with narrow black apical band about one-fifth or less the segment's length. Apical segment of genital ligula with long and narrow median projection, and with paired flagella (Figures 4, 5). In lateral view, each flagellum slender, lacking a membranous, rounded lobe on its ental surface ( Figure 4). Cercus in lateral view with ventral border of outer branch almost horizontal, tip of inner branch directed backwards and gently downwards, not markedly arched ventrad (Figure 3).

Habitat
Argia cupraurea is a lowland species, which has been found only occasionally at elevations near 1000 m above sea level. It can be observed along fairly exposed, lower courses of flat, slowflowing rivers with widely varying bottoms. These rivers may be from less than 10 m up to 40 m wide, preferably with smaller affluents nearby. Specimens can be numerous where small streams cross roads, in the neighbourhood of bridges, or where streams flow through cleared areas within forest. Argia cupraurea is absent from narrow, heavily forested streams devoid of sufficiently large, exposed, sunny areas.

Flight season
Records are from all months of the year.

Distribution in Venezuela
Argia cupraurea has been found only north of the Orinoco river, between sea level and about 1000 m elevation ( Figure 13).

Remarks
Argia cupraurea is the least common of the three metallic species. It often occurs syntopically with either A. jocosa or A. orichalcea, and at several places all three species are found together,

Diagnosis
Male (live colour Figure 1b). Labrum coppery red metallic, except free border, broadly (up to half of the width of labrum) orange. Live specimens with top of head and thoracic dorsum bright coppery red, not metallic amethyst violet. Small, blue spot near upper end of humeral suture on mesepimeron normally absent. Abdominal segment 7 black above with narrow blue basal ring, of about one-eighth or less the segment's length. Apical segment of genital ligula with short, broad median projection, and with paired flagella. In lateral view, each flagellum entally with a large, membranous, rounded lobe at its base ( Figure 4). Cercus in lateral view with ventral border of outer branch regularly curved, tip of inner branch directed ventrad (Figure 3).
Measurements: total length 37-43.5, hindwing length 20-24.    Larva (Aragua State, La Trilla, Henri Pittier National Park, 20 November 1981). Exuvia pale with only caudal gills (epiprocts and paraprocts) heavily pigmented. Head (Figure 11a) with pale spot in front of each lateral ocellus. Antenna longer than head, slender, devoid of hairs, with seven segments, the second and third darker than the rest (Figure 11b). Occiput concave; postocular lobe behind compound eye shorter than compound eye itself; hind border of postocular lobe with small spiniform setae (Figure 11a). Row of 9-10 spiniform setae also ventrally on head, along internal eye seam; similar number of such setae ventrally on postocular lobes at the level of neck. Prementum reaching to behind first coxa, with strongly convex median lobe (ligula), and with three to four spiniform laterobasal setae on each side (Figure 11c). Labial palp bearing one long seta near base of movable hook (lost on left palp) (Figure 11d). Two teeth of labial palp slender and pointed, much resembling a movable hook. Hind lobe of pronotum at lateral angle with five to six short spiniform setae. Wing cases extending to end of segment 4 (segments 1-4 being extremely extended in exuvia). Legs pale, femora with two broad, tibiae with three narrow, barely distinguishable, darker bands; all carinae with short spiniform setae, those dorsally longer; few scattered, soft hairs present, more evident on tarsi.
Abdomen pale, apparently with yet paler mediodorsal longitudinal stripe. Segments 5-10 with scattered spiniform setae on dorsum, and with more densely set spiniform setae along lateral and distal margin. Sternum 8 with about 20 scattered spiniform setae medially. Few scattered hairs mediodorsally on segments 5-10, more on segment 9. Outer genital valve armed with three irregular rows of claviform setae ( Figure 12a); valves surpassing distal border of segment 10 by less than length of stylus. Median gill (Figure 12b) and lateral gill (Figure 12c) dark but largely translucent near tip and locally along margins, probably moderately inflated in basal half and foliaceous in distal half in live larvae; a few short, soft, pale hairs along dorsal margin and around tip of epiproct.

Remarks
This is the exuvia mentioned in De Marmels (2002: 46) as "A. cupraurea". As noted there, the larva falls in the group with prominent ligula and one palpal seta, proposed by Novelo-Gutiérrez (1992). Besides the early instar and possibly misidentified larva of A. orichalcea described by Geijskes (1946) (see Novelo-Gutiérrez, 1992, the larva of A. oenea Hagen in Selys, 1865 andA. joergenseni Ris, 1913 are the only preimaginal stages known of the "metallic group" (Novelo-Gutiérrez, 1992;von Ellenrieder, 2007;respectively). Neither species occurs in Venezuela. The larva of A. jocosa differs from that of A. oenea in the smaller number of laterobasal setae dorsally on prementum, fewer claviform setae on outer valve of gonapophyses and shorter apical filament of the caudal gills. In comparison with the larva of A. joergenseni, that of A. jocosa has fewer laterobasal setae on prementum, a much longer palpal seta, and differently shaped (and coloured) caudal gills, but large series of last-instar larvae may show some of these characters being variable. Habitat Argia jocosa appears to have habitat requirements similar to those of A. cupraurea, with which it often co-occurs.

Flight season
Records are from all months of the year.

Distribution in Venezuela Remark
Common.

Diagnosis
Male (live colour Figure 1c). Labrum pale orange, with only mediobasal pit dark. Live specimens with top of head and thoracic dorsum dark coppery red. Small, violaceous spot near upper end of humeral suture sometimes present and confluent or not with pale portion of mesepimeron. Pale lateral parts of thorax grey blue violaceous, often partially pruinose near venter; abdominal segments 3-7 mostly dark dorsally with grey blue violaceous basal ring, on segment 3 triangularly expanded dorsomedially for a short distance; segments 8-10 grey blue violaceous dorsally. Apical segment of genital ligula with short, almost square median projection (Figures 4,5), with apical border undulated or fairly straight, usually bearing at each lateral angle a small point. Common stem of flagella strongly arched away from median lobe and again back towards it ( Figure 4); flagella more sclerotized than in preceding two species, and lacking membranous lobes on ental surface. Cercus in lateral view (Figure 3) similar to that of A. jocosa, but inferior branch of paraproct in lateral view normally rather short and broadly rounded.
Female (live colour Figure 2c). Labrum entirely pale, beige, with only mediobasal pit usually dark; postclypeus variable, either pale with two dark spots (Figure 6), or dark coppery with pale area at each lateral angle, and occasionally with additional pale spots mediobasally, as in A. cupraurea; black line connecting dark colour of frons with clypeus across pale vertical portion or frons ( Figure 6) usually absent or incomplete; pale occipital stripe between postocular spots present or absent; rear of head with pale band of variable width along eye border, or with larger parts pale (Figure 7). Pronotal hind lobe (Figure 8) rising from middle lobe usually at a 90 • angle; mesostigmal lobe short (Figures 9, 10); minute tubercle at mesal posterior border of depression behind mesostigmal lobe opposite to mesostigmal tubercle (Figure 9) usually absent. Dark mesepimeral stripe usually either unconnected to humeral suture or broadly separated from it in basal half of mesepimeron, sometimes narrowly ( Figure 2). Measurements: total length 33.5-37, hindwing length 20-23.

Larva.
A "probable third-ultimate female" larva from the island of Tobago was described by Geijskes (1946).

Habitat
Argia orichalcea lives in similar habitats to the two preceding species, with each of which it often co-occurs. However, this species has also been found at narrower, rocky streams, wherever these are not completely shaded.

Flight season
Records are from all months of the year.