Overview
This family of often aposematically coloured moths is the second largest in the Noctuoidea; it has about 80 genera in Australia. The monophyly of the arctiids is perhaps best supported by the presence of a thoracic tymbal organ which is lacking in some wasp-mimicking ctenuchines (Kitching 1984); the organ produces ultrasonic clicks that are thought to disrupt bat's echolocation. The prothoracic gland is another apomorphy which, however, is not found in all species; it occurs widely in the Arctiinae and Lithosiinae. Many species are distasteful. Most species are nocturnal, but some are diurnal or dawn-flyers. Of the 4 recognised families the New World Pericopinae (Watson and Goodger 1986) are absent from Australia. [Holloway 1988.]
Description
Small to medium-sized; head with short, lamellar scales; ocelli present or absent; antennae usually bipectinate or ciliate in male, simple in female; proboscis small or absent; maxillary palps tiny, 1-segmented; labial palps short, rarely long; epiphysis present, spurs 0-2-4 or 0-2-2; fore wing often without areole, Sc usually separate, R
2
to R
5
stalked, M
2
arises much nearer to M
3
than to M
1
, or absent, 1A+2A simple or with small fork; hind wing with Sc+R
1
sometimes swollen at base, usually fused with Rs to near middle of discal cell, then divergent, M
2
arising nearer to M
3
than to M
1
; often with dorsal prothoracic defensive glands; tympanal organs with tympanic membranes directed obliquely backwards; metathorax often with lateral tymbal organ; abdomen with counter-tympanal hood, if present, prespiracular; ovipositor lobes with pair of glands, some females with terminal tuft of deciduous, long scales. Egg upright, usually hemispherical with raised network on surface, usually laid in cluster. Larva usually with dense secondary setae, in tufts, from verrucae, meso- and metathorax with 1 or 2 verrucae; crochets uniordinal, abruptly shorter at end of each mesoseries; external feeders on herbaceous plants, or on lichens or dead leaves. Pupa glabrous, cremaster weak or absent; in flimsy cocoon of felted larval hairs with little silk.