Insects
The leichhardt grasshopper photo: Ian Sanderson
Despite the fact that Kakadu supports many thousands of insect species, these creatures are often overlooked by visitors. Insects are common throughout the year in the tropics and may be present in large numbers. Among the insect groups are grasshoppers, beetles, flies, termites, butterflies and moths, bees, wasps, ants, dragonflies and damsel flies, caddis flies, non-biting midges and mayflies. The great variety of insects is a result of the varied habitats and relatively high temperatures throughout the year.
Some iconic insects of Kakadu
Leichhardt's grasshopper Petasida ephippigera, Al-yurr
The Leichhardt's grasshopper is found in only 3 places in the world, and one of those places is Kakadu. The grasshopper feeds on Pityrodia bushes in sandstone country. The adults and larger nymphs are bright orange and blue and occur at the beginning of the calendar year. Their younger nymphs are brown, live close to the ground and are almost impossible to see, and this is the reason that these grasshoppers were thought to disappear for most of the year.
The traditional owners from this region call the grasshopper Alyurr, meaning children of the lightning man, Namarrgon, a powerful ancestral being. The country around Darwin and across to Arnhem Land has one of the highest incidences of lightning in the world. Namarrgon is commonly depicted in the regions rock art with axes hanging from his body, which he uses to strike the clouds. Around Kakadu the axes on his head represent grasshopper's antennae.
See abc.net.au for more information
A green tree ant | Top End Explorer Tours
Ants and termites
Green tree ants Oecophylla smaragdina
Green tree ants occur throughout the tropics of Australia, as well as Asia and New Guinea. Nests are made of leaves held together with silk produced by the larvae but applied by the adult works as if using glue-guns. Most of the nest construction and weaving is conducted at night with major workers weaving towards the exterior of the nests and minor workers weaving within the interior.
A mature colony of green tree ants can hold as many as 100,000 to 500,000 workers and may span as many as 12 trees and contain as many as 150 nests. Green ant colonies have one queen and a colony can live for up to eight years.
Cathedral Termite mounds
Termite mound | Pierre Roudier
Termite mounds are a conspicuous part of the environment. Termites are actually unrelated to ants even though they do look quite like colorless ants. They also have a social order that is reminiscent of ants, living in large colonies with workers, soldiers, and an egg-laying queen. Many species occur and by far the majority are grass-feeders rather than timber pests. The giant mounds are made of mud and termite saliva, and they are of a hardness somewhere between baked pottery and concrete. These mounds stand above the nests and help control airflow and temperature in the extensive network of subterranean tunnels.
Nests vary with species and size with age, with some thought to live up to 60 years.
Dragonflies
Cave duskhawker Gynacantha nourlangie
This is a large, dull grey-brown dragonfly with small pale yellow marks on the abdomen and was only discovered (described) in 1991. It is inactive during the day resting on the walls of cave entrances and other cool damp places. It only becomes active at dusk when is rapidly flies in search of other insects which catches and eats while still on the run.
Very little is known about the nymphal stages other than that they are aquatic and feed on other small freshwater animals.
Text and images © Dr Graham Brown
Banded flutterer Rhyothemis graphiptera
The banded flutterer | Malcolm Tattersall
Early in the morning, large numbers of these dragonflies can be seen descending down from high in the trees to sun themselves and raising their body temperatures for efficient functioning. During the late morning and afternoon, they are most often seen over water, alighting on the tops of the waterside vegetation. They hunt on the wing, gathering in swarms when food is abundant and capturing flying insects in their legs which have bristles that interlock to trap the prey.
These dragonflies have an approximate wingspan of 10cm.
