THE SENSE OF SMELL IN INSECTS.

Auckland Star, Volume LVI, Issue 192, 15 August 1925, Page 30

THE SENSE OF SMELL IN INSECTS.

Man's sense of smell may be educated. The chemist hunts down the murderer by the smell of the poison; the wine taster, tobacco dealer and other specialists show that long usage may sharpen . enormously the powers of the olfactory organ, but these experts are beaten hollow by the insects. Even a dog is left far behind in this comparison. The

experiments relating to the location of the organ of smell in insects have been going oil for years. Aristotle, Virgil and Pliny refer to the sense of smell in insects, but the seat of the organ has been the subject of keen discussion.

A female emperor moth was placed in a box covered with fine net in a room with an open window. In three hours a dozen male members of the same species came fluttering in, and in twentyfour hours the number of arrivals rose to • over a hundred. After a time the female was removed, but for some days the empty box continued to be a source of attraction to the males. How did these gallants discover the fair lady, and why did they keep coming after she had disappeared? It could only be by the sense of smell, and the odour persisting after the female Lad left the box. The mere man requires to make an appointment with his beloved if he wishes to breathe out the tender tale "beneath the milk-white thorn that scents the evening gale." He must resort to the time-wasting process of a letter or a wire, or perhaps even "to a, telephone message. He employs; that is, one or more intermediaries to assist him in bringing about the meeting;- but the insects know better, and reach the lady as if by unerring instinct. Let a man in London be told that his 'sweetheart is somewhere within a certain square mile of houses, and what chance ha-s he to find her? But mylady the emperor moth in a very short time seems to have wirelessed a hundred lovers,' who, like brave knights of old, flock to her place of hiding. They found her by the sense of smell..

Perhaps more wonderful still is the practice of a wingless species the females of which live under water. The odour from them rises to the surface and attracts the males. Then follow fierce ecstacies ending in death. "No sooner have the male insects alighted when the odour has arisen than the females rise from the bottom and drag £hem down to love and death. Deceivers ever, each of the females is an insect Lorelei. .

It has been observed that the sex which does the courting has the longer antennae, and where the serious business of courtship is shared by both sexes the antennae are equal. . In some butterflies the male produces sweet scent on the wings, a scent quite easily detected by man. Mr. Butterfly, light and airy, becomes a perfumed Paris, who succeeds in this way in stimulating the mate-hunger of the females, and they forthwith follow him.

Scientists now lay down the dictum that the sense of smell is in the antennae. No antennae—no love. Here is how a writer in the "Scientific American" describes the experiment which establishes the doctrine of the relation between antennae and smell: "Eight freshly emerged females of the common yellow sulphur butterfly and five males were liberated in a screened room, where a bunch of red clover was placed on the floor in the centre of the room. The antennae of four of the females and three of the males were clipped off close to the head. Within less than an hour all the four females »vhose smellers were intact had been anable to withstand the near odour of *.he natural food plant of their larvae, and had laid eggs on the clover. The other four had not found it, although when the plants were placed in the window sill and in their flopping about these specimens without antennae happened to alight on it, all four promptly laid their eggs also. The two males with aatennae promptly responded to the lover-like tendency, and began paying court to some of the females, while those with their antennae missing could not even be lured by sight until an enchantress happened to come near."

Other experiments equally interesting and conclusive have been made. Female moths were confined 'in transparent jars by means of netting, and others were placed under inverted glass jars whose lower ends were buried in the sand. Male moths of the same species were then released at various distances. They found their way very soon to the netted jars, but they did not locate those with the openings closed. The moths were visible through both kinds of jars, but the moths in the jars from which no odour could ■ escape were quite neglected. A further experiment was to put a thin coating of shellac on the antennae of several male moths. When this was done, they were put almost within touch of the females, but paid no attention to them. On the other hand, blinded moths with undamaged antennae have no difficulty in finding the females.

Herr yon Frisch and other workers have for years 'studied working bees with a view to discovering how they transmit news to one another. In the course of observation and experiment it was found-that the bees could distinguish the scents of various flowers, and could tell each other what flowers to look for by means of the dance in which the" bees indulged when they came home. But the significant fact is stated that the scent of the flower clings to the bed, and the dance is the means which enables her to communicate this scent ta the largest number of her friends. Having the necessary information they fly away and shunning all other flowers ; they .infallibly, find those whose scent haß been reported. ....

The sense of smell is the dominant factor in guiding many insects to food and love. Generally speaking, they cannot hear, and their eyes are not fitted for distance, bo Natwe has compensated them by extreme acuteness of smell. Tho prolongation and propagation of species is thus provided for, and here emerge questions of undying im- : portance-. ■ Why-should any.species o have its characteristics perpetuated at all? A specific' dddiir' may be the means not only of preserving life, but a particular form of it, and preserving it in purity from generation to generation. With all his intelligence-and skill man sets +»i» arnse of smell.,. , A." But what is instinct? "It is ability ?°lJr It wears W« -BiWflt of-inte 1.1 untaught. « acceffl pfiflled by self. hgence, but is n flr(J t consciousness. con< , m i m possible automata,, the^c, y , m - is that the Perp t . 0n ofwjifttlflft y this w , a y Ji.f n lo W" Some ir»tiflflst.'p«r. . m rfttieflai pafl pose has determineo. 4fld t3lo and imply the idea of idea of ends seems w ¥ en . rationality. . ' ? trancing and inspiring.