FINDING THEIR HOMES

Evening Star, Issue 20033, 26 November 1928, Page 9

FINDING THEIR HOMES

HOW BIRDS, BEES, AND BARNACLES GET DIRECTION y . H 0 SPECIAL SENSE Flying backward, the bee rose' from its new hive, moving slowly, before flying away at bullet-like speed to gather pollen. Similarly, the ant hesitated before its nest, going from side to side, before setting out for the day’s work’. Both, it is explained by Armand Rio in ‘Lectures pour Tons, 1 Paris, were “making notes’* to aid them in finding their homes again. M. Rio reminds us of the old belief that insects, birds, and molluscs are guided by a special sense, unknown to man, iu returning from a distance to their nests, and then cites numerous experiments in support of tho later theory that only the usual senses—sight, hearing, smell, and touch —come into play. Says the author, summing up

“ To begin with, wo forget that the senses of animals are much more acute than ours. What is the comparison between the sight of the pigeon, the hearing or sense of smell of a dog, and ours? Wo also forget that an animal easily retains in its memory the details of a trip made but once. This memory, which seems extraordinary to us, to tho point that wo believe animals to be endowed with a mysterious sense, is possessed to a superior degree by uncivilised man and by tho savage, whose senses miss nothing.” Usually wo believe that the carrier pigeon is capable of returning home without difficulty, regardless of the distance it has been transported. But, according to M. Rio, the actuality is quite different:—

Experience has shown that, while all of tho carrier pigeons transported for short distances only return _to their cotes, such is not the case in longer distances, when everything depends upon the individual pigeon. Do not trainers base their selection on tho sight and the muscular vigour of tho pigeons? On the muscular vigour which permit the birds to travel long distances, and on the sight which makes it possible for them to register and recognise distinguishing marks even a long distance away. W© might add that if the sharpness of vision of birds is infinitely superior to that of man, the pigeon is best endowed among all other birds. What good would this piercing vision bo if not to direct llight? What is more, the pigeon is benefited by long training. Would this bo necessary if it were possessed of a special sense? Even after training ■ and the experiences of Dusolier go to prove this—if they are taken away for a distance of 500 miles, they return only after much delay, and after having made numerous mistakes in their route. Many a time it has been demonstrated that snow and fog, which trouble the sight, have considerably hindered the return llight. Finally, m a characteristic experiment made some .years ago 5,000 pigeons wore earned for distances ranging from 90 to 300 miles. The number of pigeons returning diminished with tho distance, and of 1,500 who were sot free 300 miles away, only 300 returned after fortyeight hours. The others spread to the four corners of Europe and Africa. '‘Tho fact remains,” says M. Kaband, “that good pigeons which have been well trained, and set free m a strange zone, never return in.normal time, if they return at all. And those which do return are those that have circled about for great distances, thereby multiplying tho chances of recognising points. But, _ remember, these chances diminish with the distance. After gathering its nectar and pollen, tho bee, we are reminded, regains its hive by means of a straight line, a beeline. The same problem is indicated here: Is the insect possessed of an internal sense of direction, or is it guided' by sensory distinguishing marks? asks M. Ilio. Wo read on: “ J. H. Fabre holds that it is a sense of direction, but it must bo said tho experiences which ho quotes are by no moans conclusive. Working with solitary bees, Chalicodomcs, ho transported seven individuals for a distance of three miles, and achieved but_ four returns. In n second attempt, with lorty individuals, only liflon returned, of which number two returned in forty-five minutes and thirteen after many hours of absence. A now series of tests with ninety Chalicodomes carried in wooden boxes, for the same distance of three miles in a non-hilly country, furnished hut thirty-one good results. In a hilly country whore, wo must remember, it is harder to find the hive by means of sight, tho loss was oven greater. But twenty-two returned out of seventy. Such experiences seem to disprove rather than confirm the hypothesis of n, senso of direction, adopted by Fabre. On the contrary, precise observation and experiments rigorously carried out, establish that tho bee regains its lave by means of tho known senses. An observation of prime importance is that when bees and wasps leave their nest for the first time they always rise in flying backwards, and move away very slowly, whereas their usual flight is with the rapidity of a bullet. They use tho same tactics when their hive has been placed in a now position. Is this not because they wish to_ carry away with them an image of their hive and its surroundings? If they are earned away from their hives to a region in which they have never flown about, the bees, just like tho pigeons, return only with difficulty, or not at all. In this connection we may mention the experiments of H. Von Buttel lleepen, Romanes, and E. Yung. After having removed a hive some four miles from its original pmee, Von Buttel Reopen caught some bees before their first flight and set them free at distances varying from -10yds to 80yds. Eaeli time that a house, barn, or hedge was in front the hive the bees could not find their way back. Those, however, which had already flown about the territory quickly returned . Romanes placed a inve in tfio centre of a large garden, some 300yds from tiie sea, and permitted the bees to explore their immediate surroundings tor a single day. After having caught a number of bees which he divided into two lots, ho closed the hive. Ho set the first lot some 250yds from tho hive, but on tho borders of the sea whore the bees had not been accustomed to fly. Not a single one returned. The second lot were set tree at a.n equal distance, but m the garden itself. Ifiey all returned without delay. The experiment of Yung is equally conclusive. A lot of bees taken from a hive placed on tho borders of Lake Geneva were set free some two miles over tho lake, and not ono found its way back. A second lot, taken from the same hive, were set free some four miles, but on land, ami without a single exception they all returned. , ... The action of the sense of smell lias recently been brought to light by Verlaine. Having hidden a wasps’ nest under a cardboard case amid some other cases of identical form ami colour, ho moved tho cases about continually to other places, so that it would have been impossible for the wasps to make any definite picture of location ol their nest. He took car© to' perfume the case which covered the particular nest, using cau-de-cologne or menthol.. With no other means than their sense of smell the wasps returned immediately to their nest.

Here M. Rio invites us to consider how the question is applied to walking insects—to ants, _ for instance—which have given occasion for much study. Reading on: We will distinguish between those auts that move in columns and those that wander about singly. The first class form, as we know, long files and faithfully -follow a well-marked trail. Which sense guides them on these accustomed tracks?. The sense of smell.

It is strange that of all the naturalists JT. H. Fabrc alone denies this fact.

The experiments of Forel aro the most explicit. Ho secured a number of field ants while they weso marching along their trail. He cut the antennae, seat of the sense of smell, of some, and he covered the eyes of others with an opaque varnish. He then set them down again on their course. What was the result? The ants deprived of their antennae scurried about and finally lost themselves in all directions. The ants which had been blinded, as soon ns, they were aware of their predicament, set out in the right direction after a few zig-zag attempts. H. Picron, professor of experimental psychology at the Sorbonne. confirmed this observation with russet ants. In scratching away an extensive surface of a rock which contained the tracks of ants, or in placing an inodorous object across it, ho found that the sense of orientation of the ants was greatly troubled. But how about those ants which go alone upon their expeditions? To begin with, there is a law recognised by ■all naturalists, the going forth regulates the return. Their behaviour is quite similar to that of the bees or the wasps. An ant transported to some distance from its nest will not regain it except after long wandering about. Its return is complicated and sometimes only favoured by chance. Very often it cannot find its way back.

On its return the sense of smell plays no part. Cornctz has demonstrated that sweeping away the path in front of an ant returning to its nest will not in the least stop its course, as was the case of the ants marching; in columns. What is more, the route returned could not have been marked by its odour, for it is different from the route from the nest.

It is without question that ants travelling alone are guided by their sight, and it is a curious fact that their eyes do not register small, minute articles, but rather distinguishing marks of largo dimensions—a hedge, a haystack, or a tree. Riband has cited the case of a nest of ants of the species Caponotus maculatns which was situated at the base of a date tree. Each time the inhabitants of the nest were carried to a distance some three or four metres away from the tree they returned directly without any difficulty. When, however, they were placed in the hollow of a furrow, the crest of which hid the tree from their sight, they seemed disturbed, and found their way back only with the greatest difficulty.

Certain molluscs, notably barnacles or limpets, have also been carefully observed and made the subject of precise observations, of which ive are told: “ Limpets frequently abandon their fixed positions in order to look for food either at low tide or at high, bnt only in places that' are still moist. They go on short excursions, never more than ninety centimetres in length, and the course of their return is exactly tho same as that taken when leaving tho nest. How do they orientate themselves? If an obstacle is placed in the road which leads to the nest the limpet, will hesitate, turn to right and left, and will finally only go around the obstacle after ' several hours. If one scrapes the passageway on the rock one finds the same delay,' the same hesitation, and the same incertitude before the modified area is covered. It is due to the touch, to the tactile impressions registered principally by the foot, that , the limpet finds its way hack to ibis nsst."