ODONET - Know Your Odonates

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. 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.

Dragonflies are predatory insects with long bodies and they have wings at the side of their bodies when they rest. Damselflies are smaller, slender, and delicate insects and they have wings at the rear of their body when they rest.
Dragonflies have a broader front set of wings and not an equal shape and size of fore and hind wings. Damselflies have a narrower and equal shape and size of both fore and hind wings.
The eyes of the dragonfly are broadly rounded eyes and their eyes touch the top of their head. The eyes of a damselfly are spherical and their eyes lie flat on their head.
The young dragonfly also known as larvae respire from the rectal tracheal gills because the bodies of the dragonfly are larger and thick. The immature damselfly known as larvae respire from the caudal gills because the bodies are slender and lean.
The dragonfly travels significant distances and can fly at a speed of 60 miles per hour and hence they are called fliers. The damselfly can travel only short distances and can fly at a speed of 10 miles per hour and hence they are called perchers.
The dragonfly has a broader thorax when contrasted to the abdomen. The damselfly has a slim or narrower thorax when contrasted to the abdomen.

From a human point of view, odonates are harmless insects; that is, they do not have any direct or indirect detrimental effect whatsoever on human beings. However, from an ecological point of view, they are a highly significant group of organisms. Since odonates have well-known habitat requirements (fresh water ecosystems that vary from coastlines to tropical rain forests) and are easily identifiable, they are one of the best indicators of ecosystem quality and biodiversity. Scientists have even developed The Dragonfly Biotic Index – comprising data on geographical distribution, conservation status and ecological sensitivity – to monitor biological water quality of an ecosystem, which makes this task far more effective and simple. Population studies on odonates are widely used to monitor landscape changes also.
The capacity of odonates in controlling harmful insects such as mosquitoes, blackflies and other blood-sucking insects (both adults and their larvae) make them important bio-control agents. Many countries have successfully employed odonates to control mosquito population especially in urban areas. Needless to say, they are best friends of farmers, as they play a crucial role in controlling insect pests.
Studies have shown that globally about one in every ten species of odonates are threatened by extinction. The single most reason for this decline is the destruction of aquatic habitats. Other factors such as wetland reclamation, land filling, canalization of streams and rivers, deforestation, introduction of invasive species etc, are also posing major threat to the very existence of these magnificent insects.

* World - 6300+ species (World Odonata List 2020)
* India - 493 species (Subramanian & Babu 2020)
* Western Ghats - 196 species (Subramanian & Babu 2020)

1. A Checklist of Odonata (Insecta) of India Subramanian, K.A. & Babu, R.

1. Introduction to Odonata
2. Indian Odonates - Biodiveristy Atlas India
3. Odonates - India Biodiversity Portal