The way in which the wings come out of their sheaths is the most remarkable feature in this casting of the skin. In their undeveloped state they are folded lengthways and much contracted. A little while before they acquire their normal appearance one can easily draw them out of their sheaths; [[114]]but then they do not expand, remaining always crumpled, while, when the large piece of which the sheaths are a part is pushed back by the movements of the abdomen, they may be seen issuing gradually from the sheaths, and immediately they gain freedom, assuming dimensions out of all proportion to the narrow prison from which they emerge. They are then the seat of an abundant influx of vital juices which swell and spread them out, and the turgescence thus induced must be the chief cause of their coming out of their sheaths. When freshly expanded the wings are heavy, full of moisture, and of a very light straw colour. If the influx should take place in an irregular manner, the point of the wing is seen to be weighed down by a yellow droplet contained between its under and upper surface.
After denuding itself of the abdominal sheath, which draws away with it the wing-cases, the Sphex again is motionless for about three days. During this interval the wings assume their normal colouring, the tarsi take colour also, and the mouth-parts, at first spread out, assume their normal position. After twenty-four days as a nymph the insect attains its perfect state, tears its imprisoning cocoon, opens a way through the sand, and appears one fine morning in the light as yet unknown to it. Bathed in sunshine, it brushes wings and antennæ, passes its feet again and again over its abdomen, washes its eyes with its forefeet moistened with saliva, like a cat, and, its toilette made, flies joyfully away. Two months of life are before it.
Beauteous Sphegidæ, hatched under my eyes [[115]]and brought up by my hand, ration by ration, on a bed of sand, at the bottom of an old feather box,—you whose transformations I have followed step by step, waking up with a start at night for fear of missing the moment when the nymph breaks through her swaddling bands and the wings issue from their cases. You have taught me so many things, learning nothing yourselves, knowing without teachers all that you need to know. Oh, my beautiful Sphegidæ! fly away without fear of my tubes, my phials, and all my boxes and cages, and all my prisons for you; fly through the warm sunshine, beloved by the cicadas! Go, and beware of the Praying Mantis, who meditates your destruction on the purple thistles; beware of the lizard watching for you on the sunny slopes. Depart in peace, hollow out your burrows, stab your crickets scientifically, and continue your race, so as to afford to others what you have afforded to me—some of the few moments of happiness in my life. [[116]]
IX
ADVANCED THEORIES
There are many species of Sphex, but for the most part strangers to our country. As far as I know, the French fauna contains but three—all lovers of the hot sun in the olive region—namely, Sphex flavipennis, S. albisecta, and S. occitanica. It is not without keen interest that an observer notices in all three of these predatory insects a choice of provender in conformity with the strict laws of entomological classification. To nourish their larvæ each confines itself to Orthoptera. The first hunts grasshoppers, the second crickets, and the third ephippigers.
These prey are so different outwardly that to associate them and seize their analogies, either the practised eye of the entomologist, or the not less expert one of the Sphex is needed. Compare the grasshopper with the cricket: the former has a round, stumpy head; it is short and thickset, quite black, with red stripes on its hind thighs; the latter is grayish and slim, with a small conical head, springing suddenly by unbending its long hind legs, and carrying on this spring with fanlike wings. Now [[117]]compare both with the ephippiger, who carries his musical instrument on his back, two harshly toned cymbals, shaped like hollow scales, and who drags his obese body heavily along, ringed with pale green and butter colour, and ending in a long dagger. Place these three species side by side, and own with me that to be able to choose creatures so unlike, and yet keep to the same entomological order, the Sphex must have such an eye as not only a fairly observant person, but a practised entomologist would not be ashamed of.
In the presence of these singular predilections, which seem to have limits laid down by some master of classification,—a Latreille for instance—it becomes interesting to inquire if foreign Sphegidæ hunt game of the same order. Unfortunately information as to this is scanty or absolutely nil as regards most species. This regrettable lack is chiefly caused by the superficial method generally adopted. An insect is caught, transfixed with a long pin, fastened in a box with a cork bottom; a ticket with a Latin name is put under its feet, and all is said. This way of looking at entomological history does not satisfy me. It is useless to tell me that such a species has so many joints in its antennæ, so many nerves in its wings, so many hairs on a part of the abdomen or thorax; I do not really know the creature until I have learned its manner of life, its instincts and habits. And observe what a luminous superiority has a description of the latter kind, given in two or three words over long descriptions, sometimes so hard to understand. Let us suppose that you want to introduce Sphex occitanica to me; [[118]]you describe the number and arrangement of the wing nerves, and you speak of cubital and recurrent nerves; next follows the written description of the insect. Here it is black, there rusty red, smoky brown at the wing tips, at such a spot it is black velvet, at another silvery down, and at a third smooth. It is all very precise, very minute—one must grant that much justice to the clear-sighted patience of him who describes; but it is very long, and besides, not always easy to follow, to such a degree that one may be excused for being sometimes a little bewildered, even when not altogether a novice. But add to the tedious description just this—hunts ephippigers, and with these two words light shines at once; there can be no mistake about my Sphex, none other selecting that prey. And to illuminate the subject thus, what was needed? Real observation, and not to let entomology consist in rows of impaled insects. But let us pass on and consider such little as is known as to the manner in which foreign Sphegidæ hunt. I open Lepeletier de St. Fargeau’s History of Hymenoptera, and find that on the other side of the Mediterranean, in our Algerian provinces, S. flavipennis and S. albisecta have the same tastes that characterise them here. In the land of palms they catch Orthoptera just as they do in the land of olives. Although separated by the width of the sea, these sporting fellow citizens of the Kabyle and the Berber hunt the same game as their relatives in Provence. I see mentioned a fourth species, S. afra, as hunting crickets round Oran. Moreover, I have a recollection of having read—I know not where—of a fifth [[119]]species, which makes war on crickets upon the steppes in the neighbourhood of the Caspian Sea. Thus in the lands bordering the Mediterranean we have five different species whose larvæ all live on Orthoptera.
Now let us cross the equator, and descend in the other hemisphere to the Mauritius and Réunion Islands, and we shall find, not a Sphex but a Hymenopteron, nearly allied, of the same tribe, Chlorion or Ampulex, chasing the horrid kakerlacs, the curse of merchandise in ships and colonial ports. These kakerlacs are none other than cockroaches, one species of which haunts our houses. Who does not know this stinking insect, which, thanks to its flat shape, like that of an enormous bug, insinuates itself into gaps in furniture and partitions, and swarms everywhere that there is food to devour. Such is the cockroach of our houses—a disgusting likeness of the not less disgusting prey beloved by the Chlorion. Why does a near relation of our Sphex select the kakerlac as prey. The reason is simple: With its buglike form the kakerlac is an Orthopteron by the same rights as the grasshopper, ephippiger, and cricket. From these six examples, the only ones known to me, and from such widely distant localities, may we not conclude that all Sphegidæ hunt Orthoptera? Without adopting so sweeping a conclusion, one at least sees what the usual food of their larvæ must be.