A catalogue of the West Indian dragonflies (Insecta: Odonata)

Summary. Compilation and analysis of the existing literature together with the results of our research carried out since 2000 makes possible an updated catalogue of the West Indian Odonata. Such a catalogue has not previously been available, and dispersed and multilingual literature did not facilitate odonatological studies. The odonate fauna of the Caribbean is currently composed of 108 valid species, of which 36 (32%) are endemic to one or a few islands. The most species-rich families are Libellulidae and Coenagrionidae, together comprising 65% of the total fauna.     

Global diversity of dragonflies (Odonata) in freshwater

Larvae of almost all of the 5,680 species of the insect order Odonata (dragonflies and damselflies) are dependent on freshwater habitats. Both larvae and adults are predators. The order is relatively well studied, and the actual number of species may be close to 7,000. Many species have small distributional ranges, and are habitat specialists, including inhabitants of alpine mountain bogs, seepage areas in tropical rain forests, and waterfalls. They are often successfully used as indicators for environmental health and conservation management. The highest diversity is found in flowing waters in rain forests of the tropics, the Oriental and Neotropical regions being the most speciose. This paper discusses diversity, summarises the biogeography of dragonflies in the different biogeographical regions and gives the total number of species and genera per family per biogeographical region. Examples are given of areas of particular diversity, in terms of areas of endemism, presence of ancient lineages or remarkable recent radiations but no well-based review of areas with high endemism of dragonflies is available so far. The conservation status of dragonflies is briefly discussed. Species confined to small remnants of forest in the tropics are most under threat of extinction by human activities. Guest editors: E. V. Balian, C. Lévêque, H. Segers and K. Martens Freshwater Animal Diversity Assessment     

Fleas (Siphonaptera) infesting birds of West Siberian plain

The four species of fleas associated with birds in West Siberian Plain have been recorded. Ceratophyllus styx is a specific parasite of Riparia riparia. Ceratophyllus garei, C. gallinae, and C. tribulis parasitize various setting of birds.     

A checklist of the dragonflies (Odonata) of Kenya

A checklist of Odonata has been compiled for Kenya. It is based on an inventory of museum material, publications and personal observations made between 1978 and 1997. Changes of scientific names and synonyms are documented. The list contains 194 valid dragonfly species recorded for Kenya.     

Adaptations of dragonflies (Odonata) under desert conditions

Different types of adaptations of dragonflies to climatic conditions of the desert zone are described. The main habitats of the dragonfly nymphs are lotic and semi-lotic artificial reservoirs. The life cycles are synchronous with seasonal climatic changes, reproduction being restricted to periods of the optimal hygrothermal conditions. Some species reveal vertical seasonal migrations. The labile daily activity rhythms allow the dragonflies to avoid the effects of unfavorable conditions. Adults of many species emerge at night.     

Distribution patterns of dragonflies (Odonata) in Central Asia

The dragonfly fauna of Central Asia reveals distinct vertical differentiation. Three groups of species can be distinguished: mountain (24 species), plain (18), and plain-mountain (34) ones. The ranges observed can be classified into 7 principal types: plain, mountain, continuous boreo-montane, disjunctive Central Asian boreomontane, disjunctive Tien Shan boreo-montane, Central Asian, and Pamir-Alay plain-mountain. The leading factors determining the distribution of dragonflies are the temperature and the presence of streams suitable for preimaginal development; the former factor determines the potential ranges, and the latter, the actual ones. The present-day composition, structure, and vertical distribution of the dragonfly fauna formed during the historical time, after the development of artificial irrigation canals which provided new habitats for dragonflies.     

Sexual size dimorphism and sex ratios in dragonflies (Odonata)

Sexual size dimorphism and biased sex ratios are common in animals. Rensch's rule states that sexual size dimorphism (SSD) would increase with body size in taxa where males are larger than females and decrease with body size in taxa where females are larger. We tested this trend in dragonflies (Odonata) by analysing body size of 21 species and found support for Rensch's rule. The increase in SSD with increasing size among species can be explained by sexual selection favouring large males. We also estimated the slope of the relationship between sex ratio and size ratio in populations of the 21 species. A negative slope would suggest that the larger sex suffers from high mortality in the larval stage, consistent with riskier foraging. The slope of this relationship was negative, but after correcting for phylogentic non-independence with independent contrasts the relationship was no longer statistically significant, perhaps because of phylogenic inertia or low sample size.  © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 86 , 507–513.     

Evolution of reproductive strategies in libellulid dragonflies (Odonata: Anisoptera)

In Libellulidae, oocyte production has been assumed to be continuous, with periods of egg-laying interspersed with periods of resting/eating; however, recent work suggests that two types of oocyte production are common: either (a) continuous or (b) step-wise. These are mirrored in the arrangement of the ovarioles in the ovaries. Likewise, two types of mate-guarding behavior have been observed in Libellulidae: (1) non?Ccontact guarding and (2) tandem guarding in which the male either hovers above the female or is physically attached to her during oviposition. Using molecular (mitochondrial and nuclear) data we explored the evolution of female reproductive traits, focusing on ovariole morphology, as well as guarding behavior, in Libellulidae. Continuous egg production appears to have evolved more than once, as have tandem and non-contact guarding. We discuss how the evolution of different ovariole types and guarding behavior may have been influenced by habitat instability, dispersal and crowded oviposition sites; thus, migratory behavior or habitat availability may have been the driving force of ovariole evolution.     

A comparative analysis of senescence in adult damselflies and dragonflies (Odonata)

Any population whose members are subject to extrinsic mortality should exhibit an increase in mortality with age. Nevertheless, the prevailing opinion is that populations of adult damselflies and dragonflies do not exhibit such senescence. Here, we challenge this contention by fitting a range of demographic models to the data on which these earlier conclusions were based. We show that a model with an exponential increase in age-related mortality (Gompertz) generally provides a more parsimonious fit than alternative models including age-independent mortality, indicating that many odonates do indeed senesce. Controlling for phylogeny, a comparison of the daily mortality of 35 odonate species indicates that although male and female mortalities are positively correlated, mortality tends to be higher in males of those species that exhibit territoriality. Hence, we show for the first time that territoriality may impose a survivorship cost on males, once the underlying phylogenetic relationships are accounted for.     

Mass reproductive wanderings of dragonflies of the genus Sympetrum (Odonata,Libellulidae)

The results of observing mass flights of some dragonflies of the genus Sympetrum forming tandems are presented. These tandems always fly against the wind, some of them landing for oviposition and then joining the flight again. This variant of migration behavior has been unexplained until now. A hypothesis is proposed according to which synchronous mass flights of dragonfly tandems facilitate the most uniform oviposition in all the suitable biotopes. The general direction of the flight depends on the wind. As the wind direction changes, the flight course of the tandems changes accordingly, so that the dragonflies cross the same territory several times, which leads to a denser and more uniform distribution of eggs. It is proposed to refer to this variant of flight as reproductive wanderings. Such a dispersal strategy can maintain the most uniform population density and a more stable abundance of some dragonfly species in the territories with unstable humidity.     

Isophlebiid dragonflies from the Late Mesozoic of eastern Transbaikalia (Odonata: Isophlebiidae)

Based on the study of more than 300 isophlebiid specimens from several Late Mesozoic sites in eastern Transbaikalia (Ukurei, Tergen’, Glushkovo, and Byankino formations), new genera and species are described: Xeta olovica, Dahurium draco, and Sinitsia sophiae. The insect-bearing deposits are dated Late Jurassic according to analysis of their odonatofauna.     

Tolerance of low pH exposure by the eggs of Odonata (dragonflies and damselflies)

The development times and hatching success of the eggs of four species of Odonata (Ischnura verticalis, Lestes congener, Libellula lydia, and Sympetrum vicinum) were unaffected by exposure to soft water at pH 5.1 and 3.5. Tolerance of low pH, soft water conditions by Odonata eggs may in part account for the widespread distribution of Odonata in potentially acid-stressed regions.     

Crevice organs: Sensory structures on the wings of dragonflies (Insecta,Odonata)

Summary Crevice organs are small, elongate, innervated indentations in the hard cuticle of one wing vein of aeshnid dragonflies. There are four groups on each wing. The structure and orientation of crevice organs suggest that they detect strains in the cuticle during wing movements.I wish to thank Mr. R. Whitty and staff for technical assistance with the scanning electron microscope and Dr. E.E. Ball for helpful discussion     

An exploration of genome size diversity in dragonflies and damselflies (Insecta: Odonata)

Like most insect orders, the Odonata (dragonflies and damselflies) remain poorly studied from the perspective of genome size. They exhibit several characteristics that make them desirable targets for analysis in this area, for example a large range in body size, differences in developmental rate, and distinct modes of flight – all of which are related to genome size in at least some animal taxa. The present study provides new genome size estimates and morphometric data for 100 species of odonates, covering about 1/5 of described North American diversity. Significant relationships are reported between genome size and body size (positive in dragonflies, negative in damselflies), and there is also indication that developmental rate and flight are related to genome size in these insects. Genome size is also positively correlated with chromosome number across the order. These findings contribute to an improved understanding of genome size evolution in insects, and raise several interesting questions for future research.     

Morphological specializations of dorsal rim ommatidia in the compound eye of dragonflies and damselfies (Odonata)

We have examined the fine structure of dorsal rim ommatidia in the compound eye of the three odonate species Sympetrum striolatum, Aeshna cyanea and Ischnura elegans. These ommatidia exhibit several specializations: (1) the rhabdoms are very short, (2) there is no rhabdomeric twist, and (3) the rhabdoms contain only two, orthogonally-arranged microvillar orientations. The dorsal rim ommatidia of several other insect species are known to be anatomically specialized in a similar way and to be responsible for polarization vision. We suggest that the dorsal rim area of the odonate compound eye plays a similar role in polarization vision. Since the Odonata are a primitive group of insects, the use of polarized skylight for navigation may have developed early in insect phylogeny.