Although the sex ratio of Odonata at emergence has received much attention, we are still far from understanding the exact causes of its variability and imbalance. In this paper we studied the sex ratios at emergence in natural populations of two Gomphus species based on samples of exuviae taken from two European lowland rivers. We
In a large population of Lestes viridis inhabiting a complex, extended system of channels in the floodplain of the Upper Rhine River near Weisweil (Baden-Württemberg, Germany) detailed samples of exuviae were collected from several subpopulations. For each sample the sex ratio was determined. For statistical reasons only samples with at least 700 exuviae were considered.
Final-instar exuviae left at the emergence site by Odonata can provide information of high quality for measuring sex ratio, especially of Anisoptera. Criteria are listed according to which counts of such exuviae are acceptable for this purpose. Records of sex ratio of Odonata, published and unpublished, are critically reviewed, and 194 that meet the listed…
Three new Cephalaeschna species, C. discolor sp. nov. (holotype male; Shennongjia National Nature Reserve, Shennongjia City, Hubei province, China, 16 August 2012), C. mattii sp. nov. (holotype male; Lujiahe River, Zigui County, Hubei province, China, 18 September 2012) and C. solitaria sp. nov. (holotype male; Dalongtan in Shennongjia National Nature Reserve, Shennongjia City, Hubei province,…
Our understanding of mating systems is highly skewed toward temperate examples. This study investigated the mating system, sexual size dimorphism and seasonal variation in local distribution and abundance of male and female Telebasis carmesina, a common damselfly in Brazilian tropical savanna. In a natural reserve, daily census and behavioral observations were made throughout 1 year…
The status of the Odonata as a model taxon for studying the evolution and diversity of reproductive behaviours is shown here to have declined relative to crickets and Drosophila. Very few available data on ejaculate size, the number of sperm stored by females and the duration of sperm storage reveal poor knowledge of these areas…
Territorial behaviour associated with adult odonate feeding in a Bornean rain forest under-storey is described and its underlying causes are analysed. Immature males and females of all ages of Libellago hyalina defended perches along a narrow trail in kerangas forest, concentrating especially around patches of sunlight. Throughout the day there was displacement of individuals as…
In odonates, female specific color polymorphisms appear to be an evolutionary response to sexual harassment, but we know little about the decision rules males use when searching for variable females. For two sympatric species of Enallagma, we measured male responses to live female variants under field conditions, early and later in the day. In the…
Demography and territorial behavior of Hetaerina cruentata was studied along three lowland streams located at Norte de Santander department in the Colombian Andean region. Adult damselflies (N: 278) were individually marked, and using their recapture histories we estimated survival, longevity, sex ratio, age groups and population size at each location.
Emergence studies in Odonata provide information on the behaviour, ecology and fundamental demographic parameters in population studies. This paper reports on a study of sex ratio at emergence, pattern and duration of the emergence season, and potential cohort splitting in Petalura gigantea. Sex ratio at emergence varied among years, habitat patches and swamp types. Across