FOR YOUNG READERS

Press, Volume LXXVII, Issue 23351, 10 June 1941, Page 3

FOR YOUNG READERS

NATURE NOTES THE MAGPIE MOTH (By L. W. McCaskill) • From Woodbury, South Canterbury, a reader has sent some black, hairy caterpillars with a request for some information about their life history. In the caterpillar stage these insects are usually known as "woolly bears”; latef on each will turn into a black and white day-flying moth commonly referred to as the magpie moth and known to scientists as Nyctemera annulata. The caterpillars sent to me had been feeding on a native fireweed, but they are equally common on groundsel, ragwort, and the cinerarias in our gardens. Each was black with interrupted dark reddish lines along the sides and back. On each segment is a variable nupiber of swellings from which arise dense tufts of black hairs. ' Fbr some days after hatching the young caterpillar feeds mainly on the undersides of the leaves of the food plant. If disturbed it will let itself down by a silken thread. On reaching the ground or other solid object it curls up and intermingles some of the I6ng hairs in such a way as to protect the head. As it grows, the caterpillar becomes less secretive and feeds on the upper side of the leaf in full view of its enemies. Because of its hairi ness, birds, with the exception of the shining cuckoo, appear to ignore it. The cuckoo takes it to a branch or post, batters it, eats the interior, and discards the skin. The caterpillar may feed for up to three months. It then seeks seclusion where it toils for a day or two to make a silken cocoon, the outer part fluffy and containing some of the black hairs, the inner layers more compact and sticky. Inside this cocoon the caterpillar changes to the pupa, shiny black in colour, with rows of yellow dots on the abdomen and a yellow stripe at the tip of the wing case. Frqm four to six weeks are passed in this stage. Then the skin of the pupa breaks and the perfect insect emerges. It has a wing span of a little more than an inch and a half, a brownish black body with orange markings on thorax and abdomen. two large irregular white spots on the forewings, and a single spot on each hindwing. The background of all four wings is sooty black. The moth, flies only in the daytime and even then with a slow, almost haphazard flight as if it realised that it was in no danger from bird enemies. It seems that the moth is unpalatable to birds of all kinds —even fowls will reject it. Some scientists assume that the conspicuous appearance of the moth in sunlight with its black, gold, and whife, is an example of warning colouration. A disagreeable flavour would be no protection to an insect unless it was geneiw.lly known that it was unpalatable. \Varning colours are regarded as protecting the insect against experimental tasting.