WAYS OF THE WILD.

Auckland Star, Volume LX, Issue 224, 21 September 1929, Page 1 (Supplement)

WAYS OF THE WILD.

A NATURALIST'S NOTEBOOK. OUR LARGEST MOTH. (By A T. PYCROFT.) A large, green moth found in a city warehouse was recently handed to me. It is the male of our largest moth and has a wing expanse of four inches. The female is larger and sometimes measures live and a-lialf inches across tht expanded wings. Mr. G. N. Hudson, in his book "New Zealand Moths and Butterflies," gives an excellent account, of the habits or tliis insec:. Moths ami butterflies belong to an order of insects known as lepidoptera, from two Greek words, a scale and a wing. Members of this order possess four wings, which are clothed with numerous minute overlapping scales, usually brightly coloured. The mouths of these insects are adapted for sucking. The jaws form a hollow tube or proboscis, which is coiled up when not in use. The insect passes through three very distinct changes. The egg, the larva, such as caterpillars, grubs, maggots, etc., and the pupa, or the stage immediately preceding the adult stage. The larvae of moths and butterflies are popularly known as caterpillars. They always consist of thirteen segments, or divisions, segment number one being the head. The entire growth of the insect takes plar.e during the larval condition. This large and conspicuous moth is generally distributed .throughout the North Island, being known in Puriri country as the Puriri moth, the larvae being responsible for the large tunnels seen in this tree. The male of this moth can be readily distinguished from the female by its bright green fore wings, with an irregular row of white spots crossing the wing near the middle. The female's fore wings are green, mottled with black. The colouring of the hind wings and of the abdomen of the sexes also differs. Native and Exotic Trees Attacked. The female lays an enormous number of very small, round, yellowish eggs, which she seems to deposit quite indiscriminately. The young larvae consequently have to find their way along the ground to the stems of their food plant, a large percentage, no doubt, perishing before they succeed in doing so. This circumstance probably accounts for the great number of eggs produced. The caterpillar, when fully grown, measures from two and a-half to three inches in length. Its food plants are numerous and, according to Dr. David Miller, the following are a few of them: —Natives: Puriri, manuka, black maire, titoki and wineberry. The following exotics are also attacked:—English oak, American ash, poplar, simple, English laurel, tree lucerne and lemon trees. Lemon trees are also attacked by a beetle, tho lemon tree borer. The larva of this large moth, commonly called the puriri moth, tunnels the stems of these trees, feeding entirely on the wood, which it bites off with its strong mandibles. For the most part it inhabits the main stem of the tree, its gallery always having an outlet, which is covered with a curtain of silk and refuse, and is spun exactly level with the surrounding bark, it is, therefore, very inconspicuous. These burrows usually run toward the ground, and are mostly two or three inches from the surface of the trunk. In some instances the larvae inhabit branches, in which case, if they are small, the tunnels are made near the centre. A Complicated Burrow. Later on in its life, but probably some time before its transformation into the pupa, the caterpillar constructs a far more complicated burrow than the above. This consists of a spacious, irregular, but shallow, cavity, just under the bark, leaving a very large opening to tho air, which is entirely covered with a thin silken curtain, almost exactly the same and size as the numerous marks occurring at intervals on the trunks of many of the trees. Three large tunnels open into this shallow cavity, one in thb centre, which runs into the middle of the stem, and one on each side, which run right and left, just under the bark. These lateral tunnels are usually very short, but sometimes they extend halfway round the tree, and occasionally even join one another on the opposite side. The central tunnel has a slightly upward direction for a short distance Inwards, which effectually prevents it from becoming flooded in wet weather; afterwards it pursues an almost horizontal course, until it reaches the centre of the tree, when it appears to suddenly terminate. This, how,ever, is not the case, for, if the gallery floor be carefully examined a short distance before ita apparent termination, a round trapdoor will be found, compactly constructed of very hard, smooth silk and corresponding with the surrounding portion of the tunnel, so exactly that it ali-tost escapes 1 detection. When this lid is lifted a long perpendicular shaft is disclosed, which 1 runs down the middle of the tree to a ' depth of 14 or 16 inches, and is about half an inch in diameter. The upper end of this shaft is lined .with silk, which forms a framework on which tho trap- ' door rests when closed. The lid itself 1 is of a larger size than the orifice, which it covers, and this makes it extremely ' difficult, if not impossible, to force it open from the exterior, especially as it : always fits down very closely, as long as the insect remains in its burrow. The object of this contrivance is, lio doubt, 1 to prevent the ingress of enemies, such 1 as spiders, slugs, woodlice, etc., which are frequently found in both central and lateral') tunnels, but they are quite unablo to pass the trapdoor. The galleries of individual larvae are all wonderfully alike, the only difference observable being in the length of the perpendicular shaft, and in the direction of the horizontal burrow which is sometimes curved. Emergence of the Pupa. The last act performed by the caterpillar, prior to undergoing its transformation, is the construction of the above described trapdoor at the top of its burrow. This done, the insect retreats to the bottom. In the course of a few days the skin is cast off and worked downward to the bottom of tho burrow, underneath the last segment of the pupa. The pupa varies from two to two and a-half inches in length. The , edges of the abdominal segments are furnished dorsally with a row of small , hooklets. When about to emerge, the pupa works its W3y up the vortical tunnel by means of the above-mentioned hooklets, forces open tho trapdoor and wriggles along the horizontal burrow • until it reaches the air, only the last three or four segments remaining in the tree. Its anterior jKirtious then break open and tho moth crawl* out and ? expands its wings, resting on tho trunk of the tree, until they are of sullieient strength and hardness for flight.