My satisfaction would be equally great if I knew why the Iris-weevil’s[6] tarsus has a single nail, whereas the other insects have two, set side by side and bent into a hook. Why was one of these two little claws suppressed? Would it not have been useful to the insect? One would think so. The little Weevil thus mutilated is a climber; she clambers up the smooth stems of the iris; she explores the flowers, visiting the lower surface of the petals as well as the upper; she walks upside down on the slippery pods. An extra hook would do much to ensure her steadiness; yet the thoughtless Weevil deprives herself of it, though by law she has a right to the double claw invariably wielded by the others, even in her own long-nosed clan. What then is the secret of the little Iris-weevil’s missing finger-nail? [[263]]
A tiny claw the less, though a serious business where matters of principle are concerned, is after all a detail of no great material value; one needs a lens to perceive the irregularity. But here is something that the eye can see without the aid of the magnifying-glass.
A Locust from the green slopes of the Alps, Pezzotettyx pedestris,[7] who dwells on the higher ridges of Mont Ventoux,[8] renounces her right to wings of any kind; she reaches the adult stage while preserving the larval formation. The approach of the wedding-day makes her a little handsomer, adds a touch of coral-red to her sturdy thighs and of sky-blue to her shanks; but there all progress stops. She becomes ripe for marriage and maternity without acquiring the power of flying which the other Acridians possess in addition to that of leaping.
Among the hoppers, all endowed with wings and wing-cases, she remains a clumsy pedestrian, as her Latin affix, pedestris, informs us. Nevertheless, the cripple bears [[264]]on her shoulders a pair of skimpy sheaths which contain the organs of flight, incapable of unfolding. By what curious evolutionary whim is the pretty Locust with the azure legs deprived of the wings and wing-cases of which she carries the germs in two miserable little bundles? She is promised the gift of flight and does not receive it. For no appreciable reason, the wheels of the animal mechanism are arrested.
Stranger still is the case of the Psyches, whose females, unable to become the Moths promised in their early stages, remain caterpillars, or rather change into wallets stuffed with eggs. Wings with gorgeous scales, the supreme prerogative of Moth and Butterfly, are denied them. The males alone achieve the promised shape; they turn into plumed dandies, clad in black velvet, and are excellent flyers. Why does one—and that one the more important—of the sexes remain a wretched little sausage, while the other is made glorious by the metamorphosis?
And now what are we to say of the next, Necydalis major, a denizen of the poplar and the willow in his larval state? He is a Longicorn, fairly imposing in size as compared with Cerambyx cerdo, the little Capricorn of [[265]]the hawthorn. When one is a Beetle—and that he assuredly is—one dons wing-cases which form a sheath, enclosing the body and protecting the delicate wings and the soft and vulnerable abdomen. The Necydalis laughs at rules. He wears on his shoulders, by way of wing-cases, two short pieces which make him an inadequate jacket. It really looks as though there were not sufficient stuff to lengthen out the coat and give it a pair of tails capable of covering that which ought to be covered.
Beyond it stretch, entirely unprotected, two large wings reaching to the tip of the abdomen. At first sight, you would think that you had before your eyes some sort of huge, fantastic Wasp. Why, in an actual Beetle, this niggardly provision of wing-cases? Can the material have run short? Was the cost of prolonging the protective sheath begun at the shoulders too great? We stand amazed at such meanness.
What again shall we say of this other Beetle, Myodites subdipterus? Her grub establishes itself, I know not how, in the cells of Halictus zebra[9] and battens on the nymph [[266]]that owns the premises. The adult frequents in summer the prickly heads of the field eringo. To look at her, you would take her for a Dipteron, for a Fly, because of her two big wings uncovered by wing-cases. Examine her more closely and you will see that she carries on her shoulders two small scales, all that remains of the suppressed wing-cases. She is yet another who has not known how or rather has not been able to complete the parts of which she carries these absurd rudiments.
An entire group, one of the most numerous among the Beetles, that of the Staphylini, or Rove-beetles, cuts down its wing-cases to a third or a quarter of the normal dimensions. With excessive economy, the insect with the long, wriggling belly makes itself unsightly and goes too scantily clad.
I might continue for a long time to enumerate the deformed, the irregular, the exceptional; the “whys” would follow close upon one another and no reply would be forthcoming. Animals are uncommunicative; plants, when cunningly entreated, lend themselves better to enquiry. Let us consult them on this problem of anomalies; perhaps they will tell us something. [[267]]