Army Worms on the March

Dominion, Volume 27, Issue 35, 4 November 1933, Page 20

Army Worms on the March

(By

J. DRUMMOND,

F.L.S., r.Z.S., for ‘’The Dominion.”)

CATERPILLABS that ravished crops in Ashburton and other Canterbury districts have been identified as I'erseetania Ewiugi, or Persectauia composita, known popularly as New Zealand army worms. They are the larvae, as entomologists would say. of mediumsized night-flying moths, somewhat drab but not unhandsome, decked in browns and greys, picked out with white. These moths tire plentiful in all parts of New Zealand, on Stewart Island, on the Chathams, and doubtless, on other islands in the New Zealand geographical area. Messrs C. E. Clarke and Stuart Lindsay found them very plentiful at Lakes Manapouri and 1c Auau. The species hardly could escape the attenton of Mr. G. V. Hudson. He has given a portrait of colours of a female in “The Butterflies and Motbs of New Zealand.” and a column of letterpress recording habits of the species. Like many other foolish nocturnal moths, it is fascinated by lights. Member.-, of the kpecies quiver around a brilliant lamp in countless numbers. Ou the verandah of Mr. Hudson’s house at Karori, he attracted as many as a hundred individuals during two or three hours. It is by far the commonest insect that fell to his sugar, members of the species jostling one another to taste the sweets. In his collecting days Mr. Hudson weut out at dusk amongst plan,.* from whose flowers moths sip nectar. The most suitable for his purpose were the Veronicas, the white rata, the red rata, the scabious and the rag wort. He caried a lantern fastened to a strap around his neck or waist. Both his hands were free to catch moths. When the Howers failed him he resorted to sugaring. He mixed black treacle and rum in a tin. After sunset lie spread the mixture with a brush on tree-trunks, palings or other objects that could be examined conveniently with a lantern after dark. On some nights sugared trees swarmed with the commoner species of Noetuidae, a family to which the New Zealand army-worm belongs. Ou other nights few wore attracted. In addition to its liking for treacle and rum, the armyworm moth swarms in bewildering profusion on all sorts of attractive flowers, crowding out rarer and more aristocratic species of moths. During the day members of the species may be seen at rest. Their colours then protect them from observation, particularly if they are partly concealed amongst grass. They are unusually quick in taking to the wing. They mpy elude pursuit during flight by making a sudden stop. Their season ns perfect moths seems to l>e a long one, from September till May. They

rear two broods every season. Most of them pass the winter wrapped up in the inertia of the chrysalis stage of life, but a few perfect moths may be seen on mild evenings in the middle of winter. It may have been the same sjieeies that appalled agriculturists about sixty-six years ago. Caterpillars then marched through North Islnd districts in regiments, battalions and armies, devouring crops and leaving fields as bare as if no seed had been sown. To this day entomological text-books quote a Press Association telegram to New Zealand journals about that time, announcing that morning and evening trains between IVaverley and Nukumaru, on their way to Wanganui, were brought to a standstill by countless thousands of caterpillars on the rails, which bad to be swept and sanded before the trains could continue. Caterpillars completely threshed heavy crops of oats at Dunsandel, North Canterbury. A Dunsandel farmer watched them march out of one man’s paddock and across the road to another man’s paddock. Hastening to warn the man threatened, they put on the road 1000 sheep, which trampled countless caterpillars to death. The road was black with them. When the warm weather came they caused a horrible smell. The notorious American army-worm Cirphis unipuncta, the caterpillar of a far-flung moth, present in New Zealand, is less troublesome here than in America, Hawaii and Australia. Members of the great armies mobilised by tlie American army-worm have a retiring disposition, but when their numbers increase so largely that food is’scarce, or from some other cause, they become gregarious, and migrate in thousands, stuffing themselves with plant food as they go. Australia’s Bugoug moth, Agrotis infusa, sometimes flies on board vessels far out in the Tasman Sea. It has been reported from Invercargill, and probably is present in other parts of New Zealand, but is not plentiful here. This is fortunate, as, by its numbers, it sometimes is troublesome in Victoria and in New South Wales. A relative, Agrotis ypsilon, whose caterpillars are called cut-worms, is more plentiful in New Zealand. Cutworms do heavy damage by feeding on roots. This species is almost cosmopolitan, occurring in New Zealand, Australia, China, India, Africa. Europe. North America ami South America. In New Zealand, at this season, cut-worm caterpillars have advanced through their chrysalis stage. The perfect moths should be on the wing now. They should be much in evidence until April, paying evening visits to flowers. They are brown, their bodies are ringed with black, and their expanded wings measure two inches.