MATURE NOTES

Press, Volume LXXIV, Issue 22465, 28 July 1938, Page 7 (Supplement)

MATURE NOTES

Nancy Sheat, of Dunsandel, lias written to say that she is very interested in the red admiral butterfly and would like to know something about its life history. New Zealand is remarkable for the fact that it has only 16 kinds of native butterflies. Of these, several are rarely seen. We are fortunate then that the commdnest one which visits our gardens is also one of the most beautiful. Although many of the tropical butterflies that may be seen in the museum have much brighter colours than the New Zealand red admiral I do not think that any of them excel it in the beauty of pattern made by the various colours —red, brown, a bluish shade, black, and white. Red admirals pass the winter in the adult stage sheltering under the bark of trees, under leaves near the

ground or even inside houses or sheds. Sometimes on a very mild day in July one may be seen flying lazily about the garden, but it is usually the end of August or early September before we may -hope to see the butterflies regularly. Then they move about regularly looking for nectar in the flowers and searching for the nettle plants on which to lay their eggs. It. is one of the marvel? of nature that a butterfly such as this, feeding itself entirely on nectar, should know that an ligly nettle ip the most suitable food plant for the caterpillars. The small bush nettle is often chosen, but the butterflies seem to prefer the native tree nettle or ongaonga as it is called by the Maoris. This tree nettle is well known to those who walk. on the tracks on the Port Hills. It is quite common near the Sign of the Kiwi. • The eggs are deposited in an upright position on the undersides of the nettle leaves. With a lens they seem to be barrel-shaped, dark green in colour, and with white, ribs. The young caterpillars, which hatch from them in October and November are at first dusky yellow with black spines. In a week they moult and then are usually a brownish shade. They feed voraciously on the nettle and after soma more months become fully grown. Then they will be nearly ah inph and- a half long. The general colour is blackish-brown or perhaps pale reddish-brown, with the under surface green. The whole of the skin is covered with small whitish dotswjule numerous ’ green or black spines stick out in. all directions. On'e would think the caterpillar Would be safe enough from harm living as It does on leaves guarded by the vicious nettle spines; but to

THE RED ADMIRAL

• (By I. IV. McCasbilll

make quite sure it makes a small tent by fastening together several leaves of the food plant and feeding inside. The bunches of leaves tied together provide the best indication that caterpillars are present. To follow the life history' in detail one should feed the caterpillars on nettle leaves in a large clear-glass jar. They crawl all over the spines without being affected by the acid contained in ihem. When fully grown the caterpillar spins a patch of silk on the underside of a leaf or twig or perhaps the lid of the jar. Then it fixes the tad in this patch of silk and hangs head downwards for 20 to 24 hours. The fluid in the body goes to the lower or head end, which Swells until the skin bursts. The soft green pupa may now be seen through the crack

in the skin. Violent wriggling now takes place until the old larval skin is slipped right hack to the tail end where it appears as a small shirvelled mass. Then the pupa has to escape from this skin and attach itself to the patch of silk. It has neither arms nor legs, but uses instead the flexible joints of the abdomen. With these it grasps the shrunken larval skin, disengages the tip of the body, and sticks' it on to the silken patch. Minute “teeth’' present in the tip grasp the silk flfmly. The pupa may now turn it* self round and round until the skin ip dislodged and falls. The colour of the pupa varies from yellowish-brown, to dark purplish-brown. Sometimes it may be ornamented with gold or silver spots; always, there are small brown or black dots. After a pupa stage lasting two to three weeks the adult butterfly emerges, usually in the morning., After some hours spent in drying and stretching the wings it flies off to search for nectar, Those seen about in December and January will lay eggs which will emerge in April and May. These proceed to feast on nectar in preparation for the winter sleep with which we beganAll pupae formed do not produce butterflies. One Of the shield bugs which does good in killing the pear plug ia> also partial to red admiral pupae, ft sticks its strong sucking beak through the skin of the pupa and sucks the juices inside. But a more serious enemy of the red admiral has- recently been liberated. To attempt to cope with the white butterfly a small parasite was introduced from England. This little wasp-like insect lays its eggs in the pupa, of the white butterfly. The resulting grubs feed on the

pupa so that it never emerges as the perfect insect. Unfortunately for the reel admiral, this parasite likes to lay eggs in its pupae, with the result that'the numbers of red admirals are likely to decrease.