Threat Display - in Insects

In Insects

Deimatic displays are made by insects in groups including the mantidae (praying mantises) and Phasmatodea (stick insects). While undisturbed, these insects are usually well camouflaged. When disturbed by a potential predator, they suddenly reveal their hind wings, which are brightly coloured. In mantises, the wing display is sometimes reinforced by showing brightly coloured front legs, and accompanied by a loud hissing sound created by stridulation. For example the grasshopper Phymateus displays red and yellow areas on its hind wings; it is also aposematic, producing a distasteful secretion from its thorax. Similarly the threat display of the walking stick phasmid Peruphasma schultei is not a bluff: the insect sprays defensive dolichodial-like monoterpene chemical compounds at attackers.

Among moths with deimatic behaviour, the eyed hawkmoth Smerinthus ocellatus displays its large eyespots, moving them slowly as if it were a vertebrate predator such as an owl. Among butterflies, the peacock butterfly Inachis io is a cryptic leaf mimic with wings closed, but displays 4 conspicuous eyespots when disturbed, in a display effective against insectivorous birds (flycatchers).

An experiment by Blest demonstrated that the more an eyespot resembled a real vertebrate eye in both colour and pattern, the more effective it was in scaring off insectivorous birds. In another experiment using peacock butterflies, Blest showed that when the conspicuous eyespots had been rubbed off, insectivorous birds (yellow buntings) were much less effectively frightened off, and therefore both the sudden appearance of colour, and the actual eyespot pattern, contribute to the effectiveness of the deimatic display.

Many noctuid moths, such as the large red underwing, Catocala nupta are cryptic at rest, but display a flash of startlingly bright colours when disturbed.