Dragonflies and damselflies, collectively referred to as odonates, need no introduction. They are ubiquitous in their presence in virtually all kinds of habitats. Classified under the order Odonata—so named on account of their toothed mandibles (mouth parts)— they are among the most primitive groups of insects that appeared during the Carboniferous era, about 250 million years ago. It is widely accepted that odonates are excellent indicators of the ecosystems they inhabit. Studies have shown that dragonflies are sensitive not only to the quality of wetlands but also to major landscape changes, especially changes in the riparian zone, as has been demonstrated in studies conducted in the Western Ghats.
Unfortunately, we know very little about odonates’ habitat requirements or breeding biology, and even today, their diversity too is not well documented. Existing literature and my personal observations indicate 83 species to have been documented from the state of Karnataka. This, considering that South India has around 200 species, is an obvious underestimate.
The three volumes of ‘The Fauna of British India’ on Odonata, by FC Fraser, is a monumental work, and one wonders how anybody could dedicate so much time and energy to classify organisms that even in today’s world are not considered significant enough. Fraser surveyed Karnataka’s Uttara Kannada and Dakshina Kannada districts extensively, to the extent that Sampaje Ghat and Bhagmandala River seemed to be his favourites. It is unfortunate that the basic work done by the British of cataloguing the biodiversity of this country, including odonates, has not been carried forward with the same zest after independence.
We will now look at some of the interesting species of dragonflies (sub-order Anisoptera) found in the state of Karnataka and their behavioural traits.
Odonates exhibit sexual dimorphism, wherein the male and female of a species look so strikingly different from each other that they could be mistaken for different species. Young males, in many species, resemble adult females, thus adding to the confusion of identifying a species in the field. This is a Ruddy Marsh Skimmer (Crocothemis servilia), male.
Note how different the Ruddy Marsh Skimmer female is, from the male in the image above.
Mating is a complex process wherein the male uses his specialised anal appendages—which hold the key to identification up to species level—to hold the female at the back of her head. This position is called ‘tandem position’. The female then bends her abdomen to receive the sperms, thus forming what is termed as the ‘wheel position’. Seen here are Tri-coloured Marsh Hawks (Orthetrum luzonicum) mating, in the wheel position.
Pygmy Skimmer (Tetrathemis platyptera) is a tiny but elegant dragonfly species that breeds in shallow ponds and wells. The female lays eggs on twigs and vegetation hanging over water.
The eggs hatch in the rains and the larvae fall directly into the water below.
Dragonflies spend a major period of their life-cycle underwater and as nymphs. When they are ready to emerge, they find a rock or some vegetation to crawl on to out of the water, to begin their transformation to the adult stage. This is the time when they are very vulnerable and hence the emergence generally occurs late in the evening to avoid predation. The freshly emerged adult, as seen here, is devoid of colours, which then develops over a few hours, before it takes to its wings.
Odonates use various thermoregulation techniques such as dipping into waterbodies or sitting in a position called ‘obelisk’ position, whereby they sit perpendicular to the ground and reduce the surface area of the body exposed to the sun. This Light-tipped Demon (Indothemis carnatica) demonstrates the position.
Dragonflies are efficient predators with a success rate of more than 90%. Excellent vision with a 360 degree view coupled with incredible flight capabilities make them one of the most successful predators in the animal world. For that matter, smaller dragonflies and damselflies are not safe too and cannibalism within this group is not uncommon. In this image, a Green Marsh Hawk (Orthetrum Sabina) feeds on a Common Picturewing (Rhyothemis variegata).
One of our most common species, Wandering Glider or Globe Skimmer (Pantala flavescens), is known to be a long-distance migrant, and possibly undertakes the longest known migration by an insect so far. The route is believed to extend over the Indian Ocean between India and Africa, with stopovers in the island countries of Maldives and Seychelles.
One of the most striking dragonflies from the forests of Karnataka, the Ruby-tailed Hawklet (Epithemis marie) is a Southern Western Ghats endemic with a patchy distribution in Karnataka; Coorg is the best location to sight it in the post-monsoon season.
The Kodagu Clubtail (Gomphidia kodaguensis), as its name suggests, has been described from Karnataka’s Kodagu (Coorg) district. It is a species of riparian habitat, especially forest streams.
Estuarine Skimmer (Macrodiplax cora) is arguably the only species in the country that is salt tolerant and breeds in brackish waters, and is one of the few species that can be sighted on a beach. Though primarily a coastal species, it can be found inland as well. Being migratory and nomadic in behaviour, it is a widespread species.
Granite Ghost (Bradinopyga geminata) is a species that breeds in shallow ponds and tanks and is named so due to its habit of perching on rocks. This species has been studied as a predator of the disease-carrying mosquito Aedes aegypti, a well know vector of dengue fever. The larvae of this dragonfly are very efficient predators of the mosquitoes’ larvae, in the habitats that both occupy.