|
| Odonata (dragonflies & damselflies) |
Major Group: Insecta |
||||||||||||||||||
|
||||||||||||||||||
|
|
||||||||||||||||||
|
|
||||||||||||||||||
|
||||||||||||||||||
| Ecology: Instream habitat: Damselflies and dragonflies occur in flowing and standing waters including, streams, rivers, boggy seepages, trickles, waterfalls in splash zones, riverine pools, lakes, ponds, swamps and rock holes. Diversity and abundance is greatest in tropical and subtropical regions. Nymphs and larvae are found amongst submerged and emergent vegetation or on leaf packs on the substrata. They are clingers, sprawlers, burrowers, climbers, cryptic, hiders and crawlers. Feeding ecology: Both damselflies and dragonflies are carnivorous feeding upon insects, including other odonates, oligochaetes, chironomids, bugs, beetles, mayflies, rotifers, molluscs and small crustaceans. Larger dragonflies can prey upon tadpoles, small fish and crayfish. Many odonate species are aggressive attack predators (e.g. Aeshnidae: Anax papuensis), whilst others use stealth, patience and ambush to obtain their prey (e.g. Aeshnidae: Adveraeschna brevistyla). Species of Coenagrionidae: Coenagrion lyelli and Ischnura are known to guard their feeding areas, as increased feeding results in increased breeding ability. Habit: The odonate labium is an extensible, hinged feeding appendage. It can be rapidly extended by an increase in blood pressure, caused by contractions of abdominal and thoracic muscles, to harpoon the prey which is then grasped with modified labial palps. Most dragonfly larvae are able to propel themselves through the water by rapid expulsion of water through valves around the anus. This is useful for attack and defence. Austrocorduliidae: Austrocordulia refracta employs the unique tactic of feigning death when threatened. Life history: An adult odonate male will display territorial behaviour, constantly patrolling over the water’s surface to exclude other males from mating with prospective females, many of whom only go to the water to mate and lay eggs. Odonate adults mate in flight taking on a “wheel” position. Eggs are creamy-white turning to red-brown twenty four hours after fertilization. Most damselfly eggs are elongate, smooth and generally inserted into plant tissue. Most dragonfly eggs are ovoid to spherical, sculptured, gelatinous or with projections and usually scattered directly into the water. A one year life cycle is most common but may be shorter (two months) or longer (seven years). The life cycle generally includes nine to thirteen moults, but this varies widely between and within species depending on temperature, season and food supply. Metamorphosis begins in the last instar before ecdysis. Feeding ceases and the nymph or larva becomes the pharate adult (a composite of juvenile and adult) which then crawls up a plant stem, rock or log to leave the water prior to emergence. When the skin splits, the teneral adult (new adult with soft integument, dull colour and crumpled wings) emerges leaving behind the exuviae (empty shell) clinging to the plant, rock or log. |
||||||||||||||||||
|
||||||||||||||||||
| Information Sources: Theischinger & Endersby 2009, Watson & O'Farrell 1991, Williams 1980, Theischinger 2000, Theischinger 2001, Theischinger 2002, Hawking & Theischinger 1999, Tillyard 1917, Ingram et al. 1997, Davis & Christidis 1997 | ||||||||||||||||||
More ››› key to families 
|
||||||||||||||||||
