NATURE NOTES

Hokitika Guardian, 7 February 1931, Page 6

NATURE NOTES

EfESTKUCTIVK GRUBS

J3v Drummond, F.E.B. F.Z.B

A call tor help has come horn .\lr J. (.!. Bakin, of Hokitika, with a parcel of dark caterpillars, which, he states, are playing havoc with lawns and howling green on the West Coast. His complaint is that they tunnel under the surface for about six inches and them descend several inches into the ground. They destroy the grass. They do not seem to affect the swamp. weed on the greens, but the tunnels cause a very uneven surface.

The destructive grubs are the caterpillars of several interesting and handsome native moths. Porinn. The species that do most harm to grass lands are Purina umbraeulata and Borina cervinata. which in the caterpillar form, sometimes appear in great numbers on lawns and pastures. These caterpillars live subterranean lives, sometimes six inches below the surface. They come to the surface at night and feed on the herbage level with the ground. Mr A. H. Cockayne, Director of Plant Research, states that while feeding they protect themselves with a cloak made of particles of soil. held together loosely with silken strands. After they have fed, they descend into the ground again. They sometimes turn their baneful attention to potatoes, turnips and’other root crops. For convenience. they are called subterranean grass-cater-pillars.

The caterpillars are from an inch and n-half to four inches long, usually dark, hornv-headed. with black caps. Grass-grubs, which are the young ot native beetles, Odontria. are white or creamy. The subterranean grass-cater-pillars usually change into chrysalids about September. The perfect moths, emerging from the chrysalids, are on the wing from about the end of October well on into the new year. In one species, Porina umbraeulata, the perfect male moth is pale brownish-yel-low, sometimes greyish-brown, each fore-wing with a peculiar straight white streak, margined with black. A variety has been seen with light yellow fore-wing and pinkish hind-wings. The females seem to wear lighter and brighter colours than are favoured by the males. Porina cervinata has the white streak, sometimes broken up into spots, but is smaller than the other species, and wears light brown, yellow or grey. It is very variable in size, colour and markings.

New Zealand has no fewer than nineteen species of Porina. They belong to the family of the swift-moths, primitive in type, but rapid flyers, and counting among them, in other countries, some of the largest and handsomest moths known. New Zealand’s most beautiful Porina is rare, rich in- colours, and intricately marked. its colour-scheme being very protective when it rests with closed wings on mossy tree-trunks. Its favourite haunts seem to lie beech forests on North Island mountain sides, between on e thousand feet and two thousand feet above sea-level. It has been reported in the northern part of the South Island, but no further south. Its full name is Porina charaeterifera. Nobody has had an opportunity to observe its habits, but doubtless in the caterpillar stage, like all other Porina. it lives a subterranean life.

Tlie caterpillars of most Porinas, if not of all, rank among the curiosities of natural history on account ol attacks on them hv a fungus. C ordyceps which transposes them Ironi creatures into plants. Tn that form, they are known as vegetable caterpillars. \\ hilt? a caterpillar is in the ground, a spore of tlie fungus lodges in it. usually in the head or back of the neck. The fungus kills the caterpillar, but preserves its shape and makes it hard, l-ater. the fungus sends a stem out of the head, four or five indies above the surface, and scatters spores from tlie top of the stem. The most notable example of this remarkable relationship between caterpillar and fungus is in a species, Porina signata. fairly plentiful in the North Island, but not, mi to the present, recorded from the South Island. A caterpillar of this species is about two and three-quarter inches long, cylindrical, brown and yellow, wrinkled, with a rough, horny head, on which it wears a dark brown cap. In the perfect stage, the males of tliis species are vivacious, and may be caught in large numbers at night when they are attracted to a lamp. The females seem to have a more retiring disposition, and are seldom caught, or even seen. Dr R. T. 'fillyard states that all Porina females, when laying their eggs, have a peculiar habit of twirling their bodies round and round, ‘-praying the eggs far and wide.

After a long series of experiments on the Wellington golf links, Air Cockayne found that it is not possibb to control Porina caterpillars on : large scale, but he has recommended a method for small areas, applied in the early autumn, as soon as any damage is noticeable. His best results were obtained by mixing three parts of carbon disulphide with one part of phenyle. and using two ounces of this mixture in two gallons of water for every square yard of ground treated. In the experiments, the dilute emulsion was poured on tlie surface of the ground with an ordinary water ing-can. Within twenty-four hours all the Porina caterpillars in the area treated were killed, and the grass was not damaged.