Dragonflies and Damselflies of New Zealand by Ashbee Mike;Marinov Milen;

Author:Ashbee, Mike;Marinov, Milen;
Language: eng
Format: epub
Publisher: Auckland University Press
Published: 2019-01-15T00:00:00+00:00

Operation of the two types of labia: Naiads with a flat labium often catch their prey by piercing it with the hooks of the labial palps and then holding it in front of the jaws (top); Naiads with a concave labium scoop their prey (smaller invertebrates) or hold it with the labial palps (larger invertebrates) (bottom).

Naiads seldom chase their prey, but instead are ambush predators that spend most of the time poised, waiting for an opportunity to strike at a passing prey item. The redcoat damselfly naiad can even change colour from brownish to bright green according to the lighting and the colour of the background vegetation, rendering itself virtually invisible even when approaching prey. Sediment dwellers living in ponds, such as the sentry dragonfly naiad, can also change their normally bright green colour to match that of the pond bed, even if it is almost red. However, there are exceptions – species that do not sit and wait for prey to come to them. Naiads of the redcoat damselfly and the lancer dragonfly often cling to aquatic vegetation and stalk their prey when hunting. Baron dragonfly naiads sometimes actively swim after sluggish but relatively distant prey such as tadpoles, swimming far from their perches. They use their jet propulsion to quickly cover many centimetres.

As would be expected, the feeding strategies of adults differ considerably from those of naiads, as do the prey. Adults consume prey ranging from tiny midges to other flying insects up to their own size – even damselflies and dragonflies. In fact, teneral Zygoptera can be vulnerable to predation by all other odonates, including members of their own species. Given that prey can vary from much smaller than to almost the size of the consumer, it might appear that the size of potential prey is not important to adult dragonflies. Not so: size is critical, and before launching an attack, an adult must weigh up the possible benefits gained against the effort spent in securing and handling a prey item, especially if it is relatively large or very small.

There are three main types of adult predatory behaviour: hovering, hawking and ambush perching. Small Zygoptera fly slowly along shore vegetation and often hover while inspecting the stems for tiny prey, before gleaning settled insects from the vegetation. Gleaners must be able to detect stationary prey, and the wide-set eyes of Zygoptera make them also particularly good at judging distance, a trait needed to delicately pick off perched prey. The adult baron dragonfly is a dedicated hawker, hunting by cruising swiftly above the water. Individuals often select small territories and circle continuously within one while looking for food or mates. However, they may also range farther afield. Perchers, like the common glider dragonfly or the red percher dragonfly, are ambush predators. These species select exposed twigs, rocks or bare soil as perches where they can track passing overhead objects with short movements of the head (called ‘head cocking’), estimating the flight trajectory needed to strike the prey before they launch their explosive attack.

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.