Odonates

A short brief on odonates

1. A Seminar on ODONATA M.S.SWAMINATHAN SCHOOL OF AGRICULTURE Centurion University of Technology & Management, Paralakhemundi ,Odisha Presented By- Sunandan Swain Tapan Kumar Behera Debasish Das

2. charcters :- Rectangular stigma Large compound eyes Short, bristle like antennae They have reduced antennae since their use is limited. Eyes, are well developed: they are huge and multifaceted, thus providing excellent eyesight. Odonates are experts at detecting movement and colour (including UV and polarised light).

3. MAJOR FAMILIES:- Damselflies ( Zygoptera ) close their wings along the abdomen when at rest. Their four wings have similar shape. Damselflies are slender insects and tend to be weak flyers. Their big eyes are clearly separated and located either side of their head (a bit like hammerhead sharks.  front and hind wings are stalked (narrow at the base) and similar in size and shape. Dragonflies ( Anisoptera ) keep their wings open when at rest. Their front and hind wings have different shapes. Their eyes are so huge they often touch the top of their head.  hind wings have enlarged anal region (broader toward the base than front wings).

4. Dragonflies ( AnIsoptera ) Damselflies( Zygoptera )

5. Life cycle:- Life cycle – Odonates only have three life stages: egg-larva-adult (as opposed to butterflies, for instance, there is no pupa stage here). Eggs hatch within a few weeks into dull, brownish larvae, which can live underwate r for several months to several years depending on species. During “emergence”, larvae climb out of the water onto a leaf or twig. Their skin splits at the back of their head and thorax, allowing the young adult to emerge, unfold its wings and its abdomen. Young adults will mature over several days away from water. They head back to rivers and ponds/lakes at maturity. Adult males often keep a territory and will be on the lookout for females. Mating is often brief. Females will either lay their eggs directly into the water, or insert individual eggs inside the leaves and stems of emergent or floating vegetation.

6. Feeding:- Odonate nymphs are predaceous . Use their modified labium or mask to capture insect.( crustacean , molluscan or oligochaete) They have tactile or vibrational cues that helps them to identify the insect which are burrowed in their substrate. It is a special order in which in immature stages they have well developed eyes for hunting. Adult have large compound eye to detect insect prey ,they grasp with their legs while flying .

7. Mating of Odonata :- Males place sperm packet on second abdominal segment Males have claspers on the end of the abdomen They clasp a female behind the head Fly “in tandem” while the female bends the abdomen forward to pick up the sperm Males may clasp on to another male to complete for access to female

8. Economic importance:- They feed on small flying insects such as mosquitoes. They may also catch and eat honey bees , so regarded as pests by the beekeepers. In some parts of Europe, dragonflies are considered a threat to the poultry industry because they transmit  Prosthogonimus pellucidus , a parasitic flatworm. Dragonfly naiads become infected by ingesting cysts of the flatworm. These cysts survive into adulthood of the dragonfly and may spread to birds (particularly poultry) that catch and eat the adult dragonflies. The flatworm cysts dissolve in the bird’s intestine and infection spreads into the cloaca and reproductive organs. The Dutch have a maxim: “Hide the hens, the dragonflies are coming.”

9. Fun facts :- The compound eyes of some dragonflies may have up to 28,000 facets. Some naiads can shoot out their labium and catch prey in only 25 milliseconds. Scientists have documented large-scale migrations of dragonflies.  One swarm was observed 1,400 km off the coast of Australia. Some immature damselflies establish feeding territories, areas that are defended against invasion by other conspecifics.  Territorial species develop more rapidly and produce larger adults than other non-territorial species. Many adult male dragonflies establish and defend territories along the perimeter of a lake or stream.  Females will mate only with males that hold a territory, so population density is somewhat regulated by territory size.

10. MaleMost dragonfly naiads can move forward by “jet propulsion”.  Rapid contraction of the rectal muscles forces water out the rear end and shoots the insect forward. Male damselflies (and perhaps some dragonflies) have a special flagellum associated with the copulatory organ that can reach into a female’s body and remove sperm deposited by another male in a previous mating. Dragonflies are known by many interesting common names, including “snake doctors”, “devil’s darning needles”, and “mosquito hawks”. Can catch and eat 60 mosquitoes in one minute