Information

Damselfly identification


Can somebody identify this damselfly? Found near a stream about 15 miles west of Boston.


It looks to me like a male Argia fumipennis violacea


The damselfly in question belongs to the subspecies Argia fumipennis violacea. The species as a whole are referred to as variable dancers, however, this subspecies most commonly goes by "violet dancer".

As mentioned in another answer, this is in fact a male, which is most easily observed by the overall purple body color, as well as the blue accenting on the end segments of the abdomen. In contrast, a female will have a brown body color; both male & female have wild black markings throughout the abdomen, and transparent wings. Consider the following for comparison.

Female on left; male on right.

And then, a general image to match the one you provided:

Found near a stream about 15 miles west of Boston.

Differing from most other genera within the family Coenagrionidae, dancers are generally found along moving water, so this sounds spot on. They seem to live quite comfortably around your area, however, according to this illustration, they aren't well documented within MA itself.

(Source)


Odonata

Odonata is an order of flying insects that includes the dragonflies and damselflies. Like most other flying insects (flies, beetles, Lepidoptera and Hymenoptera), they evolved in the early Mesozoic era. [1] Their prototypes, the giant dragonflies of the Carboniferous, 325 mya, are no longer placed in the Odonata but included in the Protodonata or Meganisoptera.

The two common groups are easily distinguished with Dragonflies, placed in the suborder Epiprocta, usually being larger, with eyes together & wings up or out at rest, while Damselflies, suborder Zygoptera, are usually smaller with eyes placed apart & wings along body at rest.

All Odonata have aquatic larvae called 'nymphs', and all of them, larvae and adults, are carnivorous. The adults can land, but rarely walk. Their legs are specialised for catching prey. They are almost entirely insectivorous.


Blue-tailed damselfly

This species is present in most of Europe. [3] It is an extremely common species.

These damselflies can be found in a wide range of lowland environments, with standing and slow flowing waters, brackish and polluted water. [4]

Ischnura elegans can reach a body length of 27–35 millimetres (1.1–1.4 in) and a wingspan of about 35 millimetres (1.4 in). Hindwings reach alength of 14–20 millimetres (0.55–0.79 in). [5] Adult male blue-tailed damselflies have a head and thorax patterned with blue and black. There is a bi-coloured pterostigma on the front wings. Eyes are blue. [4] They have a largely black abdomen with very narrow pale markings where each segment joins the next. Segment eight, however, is entirely pale blue. [4] At rest, the wings of most damselfly species are held back together, unlike dragonflies, which rest with their wings out flat. The thorax of juvenile males has a green tinge. [5]

Female blue-tailed Damselflies come in a variety of colour forms. [4] Juveniles may be salmon pink, form rufescens violet, form violacea and a pale green form. The colour darkens as the damselfly ages. Mature females may be blue like the male, form typica olive green thorax and brown spot, form infuscans or pale brown thorax and brown spot, form infusca-obseleta. [5] [4]

Adults fly from April to September to early October. [4] The adult damselflies prey on small flying insects, caught using their legs like a basket to scoop the prey up while flying, or insects taken from leaves. Damselfly nymphs are aquatic, and prey on small aquatic insects or other aquatic larvae.

A male can try to interfere with a mating pair, by attaching itself to the mating male. The females always lay their eggs on the floating parts of the plants without any involvement of the male.

Blue-tailed Damselflies are superb fliers and can alter each of their four wing's kinematics in order to maneuver. A recent study has shown that they can compensate for a whole wing loss and even successfully maneuver and catch prey. [6]


Introduction to the Odonata

Both dragonflies and damselflies belong to the Odonata, which is a subgroup of insects, which in turn is a group of uniramian arthropods. Many characteristics distinguish Odonata from other groups of insects -- minute antennae, extremely large eyes (filling most of the head), two pairs of transparent membranous wings with many small veins, a long slender abdomen, an aquatic larval stage (nymph) with posterior tracheal gills, and a prehensile labium (extendible jaws underneath the head). Among living Odonata, there are twenty-five families, mostly dragonflies and damselflies. Of all their characteristics, the easiest way to tell a dragonfly or damselfly from other insects is by the size of the eyes and shape of the abdomen. If the eyes are very large in proportion to the head and the abdomen is long and thin, then it is almost sure to be in Odonata.

While both dragonflies and damselflies belong to the Odonata and share many common features, then are a number of noticeable differences as well. Even before hatching from the egg, differences in morphology of the egg distinguish dragonflies (Anisoptera) from damselflies (Zygoptera). Dragonfly eggs are round and about 0.5 mm long, whereas damselfly eggs are cylindrical and longer, about 1 mm long. Similarly, the nymphs (larvae) of the two groups differ. A larval damselfly abdomen is longer and narrower with three fin-like gills projecting from the end. Dragonfly nymphs are shorter and bulkier, and the gills are located inside the abdomen. The dragonfly nymph expands and contracts its abdomen to move water over its gills, and can squeeze the water out rapidly for a short burst of underwater jet propulsion.

Most of a dragonfly's life is spent in the larval stage where it molts from six to fifteen times. Depending on altitude and latitude, larval development varies from the common one or two years to as many as six years. At that time, the nymph crawls up out of the water and molts one last time, emerging from its old skin as an adult with functional wings. Unlike butterflies and beetles, dragonflies and damselflies do not have an intermediate pupal stage before becoming an adult. Because of this, Odonata are said to be hemimetabolous, or undergo an "incomplete" or "gradual" metamorphosis.

Both major suborders have large heads with very large compound eyes relative to the rest of their body. Each compound eye is composed of nearly 28,000 individual units (ommatidia), and together the eyes cover most of the head. More than 80% of their brain is devoted to analyzing visual information. By contrast, their antennae are tiny. Their mouths have been adapted for biting, making them efficient hunters. All Odonata have a prehensile labium, which can be extended forward from underneath the head faster than most prey can react, making their bite fatal to prey. The six legs are all located near the head and are seldom used for walking, but are more useful in catching prey and perching on vegetation to rest or lay eggs.

Both dragonflies and damselflies have two pairs of elongated membranous wings with a strong crossvein and many small veins that criss-cross in the wings, adding strength and flexibility to the wings. Both groups also have a characteristic nodus, or notch, in the front edge of each wing. In dragonflies, the rear wings have a broader base and are larger than the front pair. Damselflies, by contrast, have front and hind wings similar in shape, and as a result they fly slower than dragonflies do. Also, dragonflies do not have hinges enabling them to fold their wings together when resting, though damselflies do. This feature of the wings is the key morphological feature distinguishing adult dragonflies from damselflies.

Dragonflies can fly forward at about 100 body-lengths per second, and backwards at about 3 body-lengths per second. They are also capable of hovering in the air for about a minute. Longer periods of stagnant flight would interfere with thermoregulation. The wings of male dragoinflies are relatively longer and narrower than females in large species. Adult wingspans measure from 17 millimeters (Agriocnemis) to 20 centimeters (Coerulatus). Most temperate zone species have wingspans of 5 to 8 centimeters and wings that are from two to twelve centimeters from front to back.

The Odonata are known to be ancient insects. The oldest recognizable fossils of the group belong to the Protodonata, an ancestral group that is now extinct. The earliest fossils so far discovered come from Upper Carboniferous (Pennsylvanian) sediments in Europe formed about 325 million years ago. Like modern-day dragonflies, the Protodonata were fast-flying with spiny legs that may have assisted in capturing prey their wingspan was up to 75 centimeters (30 inches). The group went extinct in the Triassic, about the time that dinosaurs began to appear.

Fossilized specimens of another group, the Protoanisoptera (family Meganeuridae), have been found in limestone at Elmo near Abilene, Kansas, USA. The Meganeuridae differed from modern Odonata in a number of ways -- they lacked a nodus (wing notch) and pterostigma (features of the wings) and were enormous compared to modern species. Fossils of these insects with seventy centimeter wingspans have been found in Commentry, France, and a fifty centimeter specimen was found in Bolsover in Derby, both in Carboniferous layers.

Though the Carboniferous specimens are the oldest fossils of this group found to date, they were not the first specimens to be discovered. The first Odonata fossils were found in sediments from the Lower Permian, over 250 million years old. These fossils are not huge monsters like the Carboniferous fossils, but belong to relatively small Protoanisopterans and Zygopterans (damselflies). The latter seem to have changed little in structure and appearance since then. However, it is currently a question of debate as to whether members of Protodonata and the earliest Odonata had aquatic larvae, as do all modern species, since no Paleozoic larvae fossils are known. Larvae do not exist as fossils before the Mesozoic. Some workers believe that Odonata adopted an aquatic larval stage during the Lower Permian, perhaps because their prey lived in aquatic habitats. In any event, several groups of Odonata existed by the Late Paleozoic, though only three members of this group survive today.

Dragonflies are generalists, that is, they eat whatever suitable prey is abundant. Oftentimes, they hunt in groups where large numbers of termites or ants are flying, or near swarms of mayflies, caddisflies, or gnats. According to most studies, the main diet of adult odonates consists of small insects, especially Diptera (flies). Maturing dragonfly larvae feed very intensively, as do females when developing their eggs. Studies show that food shortage may limit reproductive behavior. Dragonflies do not hunt in cold weather. Damselflies, however, are not as limited by temperature and have been observed hunting during cold spells. Males are territorial, sometimes patrolling for prey for hours at a time.

Though dragonflies are predators, they themselves must be wary of many predators. Birds, lizards, frogs, spiders, fish, water bugs, and even other large dragonflies have all been seen eating odonates. However, dragonflies have many adaptations enabling them to avoid predation. They have exceptional visual responses and truly agile flight.

Although many insects perform courtship, it is uncommon among dragonflies. Anisoptera copulate while in flight, the male lifting the female in the air. Zygoptera copulate while perched, sometimes flying to a new perch. The length of time required for copulation varies greatly. Aerial copulations may last mere seconds to one or two minutes. Perched copulations usually last from five to ten minutes. Intraspecific competition amongst males for females is fierce. It has even been discovered that in some species of Odonata, the males will remove all the sperm of rival males from a female's body before transferring his own sperm. These species are equipped with a "scoop" at the tip of the male's abdomen that is used for this purpose.

The distribution of various groups and species of Odonata is highly variable. Some genera and species are widespread while others are highly local in their distribution. Some families are restricted to cool streams or rivers, others to ponds or still clear waters, and some to marshy places. The presence of dragonflies and damselflies may be taken as an indication of good ecosystem quality. The greatest numbers of species are found at sites that offer a wide variety of microhabitats, though dragonflies tend to be much more sensitive to pollution than are damselflies. Many ecological factors affect the distribution of larvae. The acidity of the water, the amount and type of aquatic vegetation, the temperature, and whether the water is stationary or flowing all affect the distribution of Odonata larvae. Some species can tolerate a broad range of conditions while others are very sensitive to their environment.

    The International Odonata Research Institute is devoted to the study of dragonflies and damselflies and is part of the Odonata Information Network.


Evolutionary ecology

Modern odonates have an exceptionally well-documented behaviour and natural history [9]. The Holarctic regions have the best described odonate faunas, while the greatest species diversity and most understudied faunas are found in tropical areas. Keys and field guides for adult odonates are available for most areas of the world [42–45], and the techniques to observe and capture individuals can be learned with relative ease, making odonates one of the few insect groups with large and comprehensive insect collections (e.g. Florida State Collection of Arthropods, Naturalis Biodiversity Center in Leiden, The Netherlands). Characteristics such as their relatively large body size and conspicuous behaviour make them an ideal insect group to study components of adult fitness in natural populations [46–49]. Below we highlight the distinct ecological traits of odonates that make them a remarkable study system for connecting field ecology with general questions in biology, including the evolution of complex life cycles, fitness consequences of divergent reproductive modes and behaviours, response to climate change, and the evolution of flight.

Complex life cycle

Most animal species (80 % of the animal kingdom) have a complex life cycle (CLC), whereby the immature and adult stages occupy different ecological niches and often undergo varied degrees of metamorphosis [50–52]. Odonata make an excellent group to explore the evolutionary causes and consequences of CLCs as the larvae are aquatic and the adults are terrestrial, and both life stages are well-studied [52]. Organisms that live in different environments throughout their ontogenies are faced with constraints to optimize responses to the various selection pressures that operate in each environment [53]. Thus, the relevant question concerns how one genome responds to contrasting selection regimes in multiple environments. Moreover, when these environments undergo divergent changes, for example through global warming which will affect aquatic and terrestrial habitats differently [51], one genome must mediate appropriate genetic responses in two different life stages across two different and changing environments. Studies of such genetic (including epigenetic) responses in odonates can be used to understand how other animals with CLCs may respond to climatic changes and in what systems adaptations are likely to occur. A major hurdle to the study of CLC evolution is a lack of knowledge about the extent to which life stages genetically covary and whether selection acts in a complementary (or divergent) way [54, 55]. The few quantitative genetic studies that have addressed this issue found support for genetic associations across life stages, but also showed that traits are capable of independent evolutionary change in response to the divergent conditions encountered during each life stage (ascidians [55], or anurans [56]). It thus seems that both genetic association and independent evolution can help to shape adaptation in some species, however, the paucity of studies to date make it impossible to draw general conclusions.

The molecular mechanisms underlying the coupling of life stages across metamorphosis are not particularly well studied (but see [57] for work on Drosophila). Thus, there is a major gap in understanding gene-by-environment interactions that would occur during major developmental transitions [58] for example, how do the immune systems of dragonflies and damselflies respond to different larval and adult environments? The recently identified immune genes in the damselfly Coenagrion puella [59] would allow testing more directly whether larval and adult stages evolve independently from one another. Furthermore, transcriptomic studies measuring gene expression patterns during larval and adult stages would elucidate the degree of plasticity in gene expression in different life stages and how environmentally induced changes differentially affect the genetic responses of larval and adult life stages [58]. Such studies would improve our understanding of how differential selection pressures across the life cycle modulate genetic and plastic adaptive processes. A genomic approach would also provide an important complement to understanding the documented carry-over effects of larval stressors to adult fitness. For example, it has been demonstrated that larval food shortage affects adult lifetime reproductive success in the damselfly Lestes viridis [60]. Moreover, transcriptomic studies could address the extent to which epigenetic changes in the larval stage are reprogrammed during metamorphosis [61], which may facilitate novel epigenetic responses at the adult stage.

Movement dynamics: dispersal

Dispersal is a fundamental ecological and evolutionary process that redistributes individuals among areas [62], thereby buffering against the demographic and genetic losses that are expected to occur in otherwise isolated populations. Perhaps the best-studied animal in terms of dispersal ecology and concomitant eco-evolutionary dynamics is the Glanville fritillary butterfly Melitaea cinxia [63]. This was one of the first non-laboratory organisms studied using high-throughput sequencing approaches [64], which demonstrates not only the feasibility but also the usefulness of obtaining genomic data from wild populations. Work on the Glanville fritillary quantified how polymorphisms at a single locus can be associated with population demography [65] and life history traits and fitness in both adults and larvae [63, 66, 67]. Odonates share many of the attractive features of butterflies for integrative research into movement dynamics, including the ease to study larval life history traits, and adults that can be marked and recaptured to quantify dispersal and mortality in the wild. In addition, odonates provide the added dimension of linking terrestrial and aquatic systems.

Dispersal can be quantified using both ecological and genetic methods. Indeed, studies on odonates have provided evidence that such different methodologies provide comparable information about population connectivity [68, 69]. Odonates have provided model systems for studies of how landscape features, such as urban areas [68] or high grounds [70], can limit dispersal and how agricultural development may affect dispersal pathways [71]. These studies also uncovered a loss of genetic diversity in isolated populations [72], but there is little information about the eco-evolutionary consequences of genetic erosion in odonate populations. The application of genomic techniques to quantify, for example, whether, and if so how, small population size limits adaptation in wild populations would be useful for informing conservation management.

Monitoring the consequences of climate change

Several damselfly species have modified their distributions and abundances over the last few decades in response to rising global temperatures [73–75]. Long-term distributional data of adults show that odonates are amongst the taxa showing the strongest poleward range expansions [73, 74], making them excellent study organisms for unravelling the still poorly documented rapid microevolutionary changes associated with range expansions [76]. This research can be embedded in the several well-documented cases of latitudinal adaptation among odonates. For example, common garden studies on larvae of the damselflies Ischnura elegans and Lestes sponsa provided a detailed picture of thermal adaptation along a latitudinal gradient in Europe. A key pattern is the evolution of thermal reaction norms and voltinism in response to differences in temperature [77]. Notably, the evolution of higher thermal optima and faster growth rates in southern latitudes has been associated with changes in digestive physiology [78], cold resistance [79], predator–prey interactions [80] and resistance against contaminants [81]. Other studies in L. sponsa indicated the evolution of larval growth and development rates and their response to photoperiod [82–84]. Genomic studies for these cases of latitude-associated adaptation may not only reveal the pathways underlying the observed phenotypic differentiation but may also identify novel aspects of adaptation along this strong thermal axis. Variation in these candidate genes can then be screened in spatial and temporal contexts as climate change continues.

Recent work aimed to quantify the genetic consequences for odonate species that are expanding their ranges has shown reductions in genetic diversity in edge-of-range populations [85, 86], and evidence for selection at the gene level [87]. Using common garden experiments, rapid evolution of both larval traits (increased growth rate and increased activity levels) and adult traits (increased flight ability and increased immune function) was demonstrated in the rapidly poleward expanding damselfly Coenagrion scitulum [88, 89]. The few studies on genomic signatures of range expansion in both plants and animals did not link genetic changes to phenotypes and did not unravel the evolutionary processes involved [76]. In a first effort to do so, a single-nucleotide polymorphism (SNP) study focused on C. scitulum revealed one SNP associated with increased flight performance to be under consistent selection in the populations at the expanding range edge [87]. This indicates that evolutionary changes among independent edge populations are driven by the range expansion process per se. This study illustrates the added value of integrating genomic, phenotypic and environmental data to identify and disentangle the neutral and adaptive processes that are simultaneously operating during range expansions. An important future step will be to identify other determinants of dispersal ability at the molecular level. For example, some sequence data on candidate ‘dispersal’ genes, such as pgi, hif1alpha or sdhd [90, 91] are available for odonates [27]. Applying genomic studies to the other well-documented range expansions in odonates may therefore considerably add to the limited knowledge on how species evolve during range expansions.

Climate change and hybridisation

In addition to a loss of species diversity, many range expansions are creating de novo sympatric areas between formerly allopatric taxa, and increasing evidence is suggesting that this can modify species interactions [92]. Furthermore, evidence is growing that species interactions in these newly created sympatric zones are leading to the breakdown of species barriers and rapid hybridisation (reviewed in [93]). Thus, species identities in these de novo sympatric zones may be unclear. Molecular methods for species identification could help us to resolve species identities via genetic means and provide clues about the general processes underlying the creation of biodiversity. For example, by studying the genomics of species hybridisation and species introgression in odonates, we would obtain a better knowledge of the processes underlying the creation of novel genetic adaptations. In general, it is thought that adaptive genes have a greater chance to cross species boundaries than key “speciation genes” or genes residing inside “genomics islands of divergence”, which should both be more resistant to introgression [94, 95]. Genomic studies on introgressive hybridisation in damseflies are being initiated and have the potential to uncover if certain genomic regions are repeatedly inherited from the same parental species. These studies may be able to elucidate the size of genomic linkage islands and how the inheritance of genomic regions correlates with morphology and ecology.

The vulnerability of odonates to anthropogenic changes makes informed conservation measures a priority, given the likely impact that these changes may have on the overall species diversity, food web structure and ecosystem stability. A recent comparative study on several damselfly species assessed the potential to use quantitative predictions of reproductive isolation as an indicator to assess species’ hybridisation risk [96]. The study found a positive correlation between the degree of reproductive isolation and genetic distance between species, as has been shown in fruit flies [97] and butterflies [98]. This clear link between species divergence rates and the likelihood to hybridise strongly suggests that genetic divergence between taxa can be used as a proxy to predict hybridisation rates of species that come into contact following climate induced range expansions [96]. This link can be used to inform conservation efforts, particularly for odonate species that are already endangered (e.g. Ischnura gemina, [96]).


Dragonfly Biology

Like all insects, the dragonfly is made up of three main body parts: head, thorax and abdomen. The head is a tough, rounded capsule, hollowed out at the back to allow efficient attachment of the neck and to increase head mobility. The mouth is a complex hodgepodge of structures that you would not want to encounter in a dark alley. The upper lip, or labrum, is often considered part of the face. The lower lip, the labium (sometimes called the chin), is made up of three lobes. The labrum and labium function together to capture and secure prey while the jaws do the chewing. The jaws, which work from side to side, are made up of one pair of upper mandibles and two pairs of lower maxillae. These jaws, a series of incurved meat hooks, are worth a close inspection and should be approached with caution in larger species. Species such as dragonhunters and larger darners can drawn blood when they bite.

The face is a conglomeration of plates separated by seams called sutures. The sutures are often darkened into stripes. The upper half of the face is the frons, and the upper surface of the frons is a shelf-like protuberance on which various diagnostic markings may be found. The compound eye is composed of nearly 30,000 lenses, which work in consort to provide a rich visual image to the dragonfly. They are sight-based creatures who, with a quick turn of the head, are able to scan 360 degrees as well as above and below. Their vision probably allows them to discern individual wing beats, which to us would appear as a blur. They can see ultraviolet and polarized light. Many species also see well in dim light.

Their two short bristly antennae are thought to function as windsocks or anemometers, measuring wind direction and speed, thereby giving them a method with which to assess their flight. By the way, dragonflies have no sense of hearing, only a rudimentary ability to smell and are unable to vocalize.

Thorax

The thorax is the center for locomotion. It is a muscular powerhouse, controlling head, wing and leg movements. Dragonflies are unusual in their wing movements. Most insects’ wings are attached to plates of the chitonous exoskeleton that are, in turn, attached to muscles that move the plates that move the wings. Dragonfly wings, on the other hand, are directly connected to large muscles within the thorax. The interior of the thoracic exoskeleton is massively braced and strengthened to withstand the pressures of these large flight muscles. This bracing can be seen through the exoskeletons of lightly-pigmented individuals such as the Wandering Glider, the Four-spotted Skimmer and the Common Green Darner.

Thoracic stripes are present in many species. In order to easily communicate the positions of these stripes, the thorax can be separated into three sections: top, shoulder and sides. The top stripes of the thorax will be found in the region between the head and the wings and are best viewed from the front of the dragonfly. The side stripes of the thorax are found below the hindwing attachment point and back toward the abdomen. The shoulder stripes are found below the forewing attachment point, in between the top stripes and the side stripes. Back to the top

Wings

The anatomy of wings and their venation can be very complicated, and one could make a life’s work of just studying them. Most dragonflies can be identified to the level of genus and many to the level of species by just knowing the wing venation. The veins in the wings of dragonflies start as flattened tubes in the compact, tightly folded wings hidden inside the skin of the aquatic nymph. During transformation to adulthood, the veins fill with hemolymph, or insect blood, causing the wings to unfurl. Most of the hemolymph is drawn back into the body after the wings have been fully expanded. The empty tubes and the membranes dry, leaving crisp, tough wings.

The most obvious feature of a clear, unpatterned wing is the stigma, located on the leading edge of each wing out towards the wingtips. It is thought that the stigma may be used for signaling mates or rivals and may also act as a tiny weight that dampens wing vibrations. The nodus, located at the shallow notch midway down the leading edge of each wing, is an intersection of several large veins and is a point of both strength and flexibility. Because of the structure of the venation around the nodus, the wing is allowed to bend downward (during an upward stroke of the wing) but not upward (during a downward stroke of the wing), resulting in a powerful flight stroke without losing much energy on the return stroke. The wing triangles are located about twenty percent of the way from the wing base toward the tip. The relative size and orientation of these triangles on a dragonfly’s wings can be a clue as to the dragonfly’s family. Originating from an inner, rear corner of the hindwing triangle, the anal loop reaches down into the expanded base of the hindwing. The degree to which the anal loop is present varies from one family to the next. Back to the top

Abdomen

The abdomen always has ten segments. Segments 1 and 2 appear to be integrated into the thorax and are sometimes difficult to tell from the thorax. To find a particular segment, it is usually best to start with segment 10, far out at the tip, and count backwards. Because of its segmented nature, the abdomen is very flexible and is able to arch up or down (but not side to side). Learn to count abdomen segments as many of our descriptions are based on them.The male abdomen is often narrower (“waisted”) at segment 3, whereas the female abdomen is almost always more robust. Back to the top

Reproductive System

The male testes are located in segment 9. Due to the unique nature of dragonfly copulation, the male must transfer sperm to his secondary genitalia, called the hamulus, located in the underside of the second and third segments. The hamulus is a complicated set of “surgical tools” that the male uses for removing the reproductive “investment” made by other males during previous matings. Other parts of the hamulus are then used by the male to fertilize the female with his own sperm. The terminal abdominal appendages of the male are called claspers. The claspers are formed by a pair of upper appendages, called cerci, and a single lower appendage, an epiproct. In some species, the males possess auricles on the sides of segment 2 whose function is to help direct the female’s genitalia to a proper fit with the male’s secondary genitalia during copulation.

The female terminal appendages consist of a pair of cerci, which have little or no function. In some species, namely the Shadow Darner, they are very brittle and tend to break off. Underneath segment 8 there is either an ovipositor or a subgenital plate, depending upon the species. Both structures are for laying eggs and extend over segment 9 and possibly beyond. Back to the top


There are sufficient visible differences between species that keys are generally not needed to identify species in this group. The field guides and resources described below provide excellent drawings and images that enable identification from careful observation. Nymphs are more similar and often require a good lens or microscope to observe the relevant features but can still generally be identified using a relevant guide.

Online

British Dragonfly Society - excellent images of all UK species.

NatureSpot Videos:

  • The Lifecycle of Dragonflies and Damselflies: https://www.youtube.com/watch?v=tTkPIQgzxac
  • Dragonflies and Damselflies in Leicestershire and Rutland (VC55) - recent trends: https://www.youtube.com/watch?v=w9Zt8CknmlE

Printed

Britain's Dragonflies: A Field Guide to the Damselflies and Dragonflies of Britain and Ireland by Dave Smallshire and Andy Swash (Wild Guide). This photographic guide contains information on biology, habitats and the identification of both adults and larvae. All fifty-six species on the current British list are covered with photos of all colour forms, plus seven possible vagrant species. There are full colour plates throughout and individual species accounts include flight times, maps and key ID points highlighted in red, Although mainly photographic, there are some useful pages showing the key features of similar species in the early part of the book. It also contains detailed, easy-to-use identification charts for adults and larvae.

Field Guide to the Dragonflies and Damselflies of Great Britain and Ireland by Steve Brooks (BWP).The revised edition of this guide covers 57 of the resident and migrant species on the British list, including recent additions. As above, there are sections on biology, habitats, larval identification and distribution. There are also the usual individual species accounts with colour illustrations by Richard Lewington, showing top and side views of adults, with enlargements of key features. This also includes a larval key.

Field Guide to the larvae and exuviae of British Dragonflies, Damselflies (Zygoptera) and Dragonflies (Anisoptera) by Steve Cham. A practical approach to identification of these important life stages without the need for keys. The book contains high quality colour photographs showing all the key distinguishing features of the larvae of all species that occur in Great Britain and Ireland.

Field Guide to the Dragonflies of Britain and Europe by Klaas-Douwe B Dijkstra and illustrated by Richard Lewington (British Wildlife Publishing).A comprehensive field guide to the dragonflies and damselflies of Britain and Europe. It has almost 1000 illustrations and photos showing top and side views as well as important features. Includes Europe, North-western Africa and western Turkey.

Apps

iRecord Dragonfly - www.brc.ac.uk/app/irecord-dragonflies - A web-based app produced by CEH / BRC in collaboration with BDS. This will include photos of resident and regular migrant species and recording facility for BDS.

Dragonflies & Damselflies of Britain & Ireland by BirdGuides Ltd (2011), Based on the book ‘Britain’s Dragonflies’. An app for iPhone and iPad. £9.99. Available from the iTunes store. A comprehensive field guide to the identification of all 46 dragonfly and damselfly species that have been recorded in Britain and Ireland. It aims to help the dragonfly-watcher – beginner or expert – to identify any species they encounter.


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With iridescent blues and greens, damselflies are some of the most beautiful flying insects as well as the most primitive. As members of the insect order Odonata they are related to dragonflies but are classified in a separate suborder. These aquatic insects are a delight to the eye and a fascinating creature of study. In Damselflies of Alberta, naturalist John Acorn describes the twenty-two species native to the province. Exhaustively researched, yet written in an accessible style, the author's enthusiasm for these flying neon toothpicks is compelling. More than a field guide, this is a passionate investigation into one of nature's winged marvels of the wetlands.


Threats

The biggest threat to dragonflies and damselflies probably comes from loss of habitat, changes in land management and urban/industrial development.

Pollution is a major cause of concern, especially sewerage, industrial effluents, diesel, excess sediments, run-off from fertilisers used in agriculture, wind drift from insecticides, and the consequences of using herbicides on marginal vegetation. Pollution may be particularly devastating in streams, rivers and pools or lochs with inflows.

Aquatic habitats used by odonates (damselflies and dragonflies) may be lost through drainage or over-abstraction of a watercourse. Serious impacts on flowing water species can also occur following the canalisation of rivers or as a consequence of certain flood prevention schemes.

Species with a northerly distribution, such as the Azure hawker, the Northern emerald and the White-faced darter mentioned earlier, may be severely affected if temperatures rise as a result of climate change. The drying out of small bog pools, as a result of either drainage or climate change, or a combination of both, could be particularly disastrous for the Azure hawker with a larval life that can extend for up to four years

Changes in land management may take several forms, and one of the most harmful to Odonata habitat in Scotland, side by side with destructive peat cuttings on an industrial scale, may well be afforestation. The Northern damselfly, for instance, has been lost from one of its long-established site due to the combined effects of afforestation and drainage. Conservation work in Speyside, blocking drains to improve the habitat for birds has, unintentionally, created suitable temporary habitats for this damselfly species, but these provisional havens may become unsuitable if the water levels cannot be maintained.

Inappropriate habitat management can have catastrophic impacts. Drastic modifications to water bodies or their surrounding vegetation can eradicate populations. At the other end of the scale, a complete lack of management can result in the water being shaded out by surrounding trees and shrubs or choked with silt and plants accumulated over the years.

Overstocking ponds with fish has immediate negative impacts as they are natural predators of dragonfly larvae. In addition, bottom-feeders such as carp disturb sediments, which can muddy waters to such an extent that submerged plants cannot grow any longer and in turn make the site unsuitable for dragonflies.

Widlfowl can cause physical damage to the banks through much trampling and grazing of the marginal vegetation and are a source of chemical pollution due to nutrient enrichment from their droppings. Disproportionate nutrient input can, for instance, cause algal blooms and excessive growth of duckweed, which in turn prevent any light getting into the water, any plant growth and any aquatic insect life.

Excessive wave action from boat drift and other unnatural fluctuations in water levels can have severe impacts on odonate populations as well, either through direct impact at the peak of dragonfly emergence, or indirectly through damage to marginal vegetation and erosion.


Surge in research

Species like the Sri Lanka emerald spreadwing (Sinhalestes orientalis), which was not recorded for more than 150 years and once thought to be possibly extinct, was later rediscovered from the Peak Wilderness Mountain range.

The smoky-winged threadtail (Elattoneura leucostigma), which was not seen for more than 40 years, was recently recorded from several locations in the highlands including Horton Plains National Park, which is one of the most visited parks in the country.

Similarly, Nietner’s grappletail (Heliogomphus nietneri), a species only known from a single specimen for more than 120 years, was recently recorded from multiple locations in the Knuckles Mountain Range, which is one of the most popular travel destination among local travelers.

One reason for some of these rarities to be overlooked for prolonged periods is the fact that they are highly seasonal. Certain species like the shadow damsels of the genus Ceylonosticta, especially in the highlands, are only observed for a couple of months during or immediately after the southwestern monsoon. They are also very habitat specific and usually occur only in their preferred habitats, thus making it crucial to be in the right place at the right time to find these species.

Over the years, researchers and naturalists have gathered a considerable amount of data on these species, gradually widening the horizons of our understanding of the endemic dragonflies and damselflies of Sri Lanka. With recent findings, we now have a better understanding on where and when these amazing species occur.

The stripe-headed threadtail (Prodasineura sita) is a common endemic damselfly found in streams and riverine habitats. Image courtesy of Amila P. Sumanapala.

However, despite decades of research and explorations, some rarities still remain hidden. Species such as Flint’s cruiser (Macromia flinti), which has only been collected once, in 1970, and Keiser’s forktail (Macrogomphus annulatus keiseri), last collected in 1970, have evaded researchers despite their search attempts. Whether they are still surviving the various threats and pressures on dragonflies and damselflies, their habitats and ecosystems, is still an unanswered question.

Further explorations targeting the missing, lesser-known and undescribed species research on understanding their biology, ecology and biogeography as well as research focused on investigating the impacts of climate change, pollution and other environmental changes on their survival, are crucial to supporting the conservation of these enigmatic Sri Lankan endemics.

It is hoped that with the use of novel research and conservation tools and opportunities such as citizen science, we will be able to create a better future for the endemic dragonflies and damselflies of Sri Lanka.

Amila Prasanna Sumanapala is a field researcher studying the faunal biodiversity of Sri Lanka. He is currently doing postgraduate work on Sri Lankan Odonata, an order of carnivorous insects that include dragonflies and damselflies, and has more than a decade of experience in biodiversity research and assessments. He serves as an active member of several conservation organizations.

This article by Amila Prasanna Sumanapala was first published on Mongabay.com on 18 May 2021. Lead Image: A shining gossamerwing (Euphaea splendens), a damselfly found only in Sri Lanka, courtesy of Amila P. Sumanapala.


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