ENTOMOLOGY

Nelson Evening Mail, Volume 79, 13 May 1944, Page 3

ENTOMOLOGY

RELATION OF SCIENCE TO HUMAN PROGRESS

REACTIONS OF INSECTS TO ENVIRONMENT The science of entomology, once the liobby of the amateur collector and field naturalist, has grown in comparatively recent times to the rank of a leading profession, the studies of which are closely interwoven with human progress, said Dr D. Miller, entomologist at the Cawthron Institute, in an address to the Canterbury branch of the Royal Society of New ealand. His object, he said, was to demonstrate the scope of entomological science by reviewing some of the phenomena of insect behaviour displayed by the reactions of insects to the physical and organic influences ol' their environments. Describing the influence of climate on insect life. Dr Miller said that butterflies. popularly associated with the warmer climates, • also inhabited regions within the Arctic circle. In North Siberia, with a winter temperature of minus 60 degrees Fahrenheit, and on the polar coast of Grant Land, within 500 miles of the North Pole, there was a scanty vegetation and numerous species of brightly coloured butterflies. The feeding period of the caterpillars was limited to tile brief summer of some six weeks, and as the temperature fell the caterpillars became hard and brittle. In spite of this they recovered with the increasing warmth of the following summer. Two to three years were occupied in the development of these insects from egg to acii.lt, as compared with a few \vock* in warmer climates There wove a few insects which could resist the abnormally high temperatures of deserts up to 144 degrees Fahrenheit, and there were exceptions to the general rule of the cessation cf normal activities under falling temperatures, when insects normally went into hibernation. The Chilean sawfly, imported for the control of piripiri, reversed the normal seasonal history of iiiscett,. INFLUENCE OF LIGHT Everyone had observed the influence of light on insects, said Dr Miller. That many night-flying insects were attracted to artificial light appeared to be not wholly clue to the influence of light. Temperature and humidity might enter into the reaction, which might even bo activated by some internal force, which as in the case of the cuckoo which, when reared in captivity, automatically moved its wings continuously during the period of migration, as if in flight. The first gorse seed weevils imported into New Zealand from Europe had to be studied under quarantine. This involved enclosing them with the gorse flowers and seed pods in wire gauze cases of small mesh. The weevils produced no eggs, and the solution was found in the assumption that as gorse flowers demanded sunlight so would the insects infesting them. The original gauze cages excluded about 60 per cent, of light, and a new type of cage was designed to allow the maximum entry of light. Tn these conditions the weevils produced eggs freely. “The use of the vacuum has been extensively developed for the purpose of fumigating stored products, plants, books, furniture, etc,” said Dr Miller. “Indeed, its use is enforced under the quarantine laws of several countries and is being adopted in New Zealand. The principle involved is to stimulate the insect metabolism and ensure the penetration of the fumigant.” INSECT AVIATORS Flying insects were widely dispersed by winds, and.there were others which could not fly at all and depended entirely on air currents as a means of distribution. Among the latter were the scale insects. In North America the Gypsy moth largely depended on the agency of wind for dispersal. The young larvae were provided with aerostatic hairs which enabled the insects to float on the air for 20 to 25 miles when the wind velocity was no more than eight miles an Dour, “That some insects are omnivorous in the range of plants they attack, while others restrict their diet to one family genus, or even species is common knowledge.” said Dr Miller. “That insects at times extend their food range to new plants is easily enough understood where the new plants are related to those of the normal food range. . . But more difficult to explain is the case where an insect confined normally to one plant suddenly adopts another of a totally different kind.” An illuminating example of this was the apple capsid in England which normally fed on the willow. Between 1900 and 1910 it turned its attention to the apple, and since then had become one of the most serious apple pests. It was of great interest to note that the apple and willow’ strains of the apple capsid tended to adhere to their respective hosts. The classical example of biological races was the apple maggot or blueberry maggot in the United States. This fly, originally confined to blueberry and cranberry, had spread to apples in recent time. Two races had developed, the one on apple larger than that on blueberry :.K larvae, pupae, and adults, yet. morphologically similar in all details. All attempts to transfer the two races to their opposite hosts had failed.