Dumb likewise, apparently as a consequence of the excessive length of his hind-legs, the big Grey Locust (Pachytilus cinerescens, Fabr.) has a peculiar way of diverting himself. The giant often visits me in the enclosure, even in the depth of winter. In calm weather, when the sun is hot, I surprise him in the rosemaries, with his wings unfurled and fluttering rapidly for a quarter of an hour at a time, as though for flight. His twirling is so gentle, in spite of its extreme speed, as to create hardly a perceptible rustle.
Others still are much less well-endowed. [[373]]One such is the Pedestrian Locust (Pezotettix pedestris, Lin.), the companion of the Alpine Analota on the ridges of the Ventoux. This foot-passenger strolling amid the paronychias (P. serpyllifola) which lie spread in silvery expanses over the Alpine region; this short-jacketed hopper, the guest of the androsaces (A. villosa), whose tiny flowers, white as the neighbouring snows, smile from out of their rosy eyes, has the same fresh colouring as the plants around him. The sunlight, less veiled in mists in the loftier regions, has made him a costume combining beauty and simplicity: a pale-brown satin back; a yellow abdomen; big thighs coral-red below; hind-legs a glorious azure-blue, with an ivory anklet in front. But, being incapable of going beyond the larval form, this dandy remains short-coated.
He has for wing-cases two wrinkled slips, distant one from the other and hardly covering the first segment of the abdomen, and for wings two stumps that are even more abbreviated. All this hardly covers his nakedness down to the waist. Any one seeing him for the first time takes him for a larva and is wrong. It is indeed the adult insect, [[374]]ripe for mating; and the insect will remain in this undress to the end.
Is it necessary to add that, with this skimpy jacket, stridulation is impossible? The big hind-thighs are there, it is true; but what is lacking, for them to rub upon, is the grating surface, the edge of the wing-cases. Whereas the other Locusts are not to be described as noisy, this one is absolutely dumb. In vain have the most delicate ears around me listened with might and main: there has never been the least sound during the three months’ home breeding. This silent one must have other means of expressing his joys and summoning his partner to the wedding. What are they? I do not know.
Nor do I know why the insect deprives itself of wings and remains a plodding wayfarer, when its near kinsmen, on the same Alpine swards, are excellently equipped for flight. It possesses the germs of wing and wing-case, gifts which the egg gives to the larva; and it does not think of using these germs by developing them. It persists in hopping, with no further ambition; it is satisfied to go on foot, to remain a Pedestrian Locust, as the nomenclators call it, when it [[375]]might, one would think, acquire wings, that higher mechanism of locomotion.
Rapid flitting from crest to crest, over the valleys deep in snow; easy flight from a shorn pasture to one not yet exploited: can these be negligible advantages to the Pedestrian Locust? Obviously not. The other Acridians and in particular his fellow-dwellers on the mountain-tops possess wings and are all the better for them. What is his reason for not doing as they do? It would be very profitable to extract from their sheaths the sails which he keeps packed away in useless stumps; and he does not do it. Why?
“Arrested development,” says some one.
Very well. Life is arrested half-way through its work; the insect does not attain the ultimate form of which it bears the emblem. For all its scientific turn of phrase, the reply is not really a reply at all. The question returns under another guise: what causes that arrested development?
The larva is born with the hope of flying at maturity. As a pledge of that fair future, it carries on its back four sheaths in which the precious germs lie slumbering. Everything is arranged according to the rules of [[376]]normal evolution. Thereupon, suddenly, the organism does not fulfil its promises; it is false to its engagements; it leaves the adult insect without sails, leaves it with only useless rags.
Are we to lay this nudity to the charge of the harsh conditions of Alpine life? Not at all, for the other hoppers, living on the same grassy slopes, manage very well to achieve the wings foretold by the larva’s rudiments.