The next Order from which we shall choose examples will be the Hemip´tera, containing the Land and Water Bugs and some other forms. Our chief concern, however, is with the Water Bugs. In this Order the metamorphosis is incomplete; the mouth is adapted for sucking the juices of plants and animals; and there are usually four wings. In the Land and Water Bugs, part of the fore wings is harder than the hind wings; in the other winged members of the Order both pairs of wings are membranous. The front wings are called hemel´ytra or halfel´ytra, to distinguish them from the el´ytra or wing-cases of Beetles, which are chitinous throughout. Fig. 41 shows the hemel´ytron and hind wing of a Land Bug, and the names given to the different parts of the front wing.
Fig. 41.—A Land Bug (magnified). a, corium; b, clavus; c, membrane.
The Water Scorpion (Nepa cine´rea) is not difficult to procure, or to keep in confinement when it is caught. It would be straining language to call it a handsome creature, yet it well deserves careful study, on account of the wonderful modification of the first pair of legs, and it is from the resemblance of these to the pedipalps of the scorpion that the insect derives its popular name. Its length is about an inch and a quarter, from the tip of the beak, or rostrum, to the end of the breathing-tube. Its greatest width is a little over a quarter of an inch (Fig. 42). The general hue harmonizes well with the mud, but the upper surface of the abdomen is a warm red, ‘and is thick set with hair, so as to afford a very agreeable sight.’
Fig. 42.—Water Scorpion.
It is extremely common in shallow pools, and its favourite haunt is near the shore, where it will lie, almost buried in the mud, with its raptorial legs elevated, ready to seize on any passing insect, and its breathing-tube just pushed through the surface-film. I learnt this habit of the insect on the first occasion on which I tried to collect specimens of it. I had been told that a certain piece of water swarmed with Water Scorpions. This, I afterwards found, was quite correct; but though I worked the pond from end to end, a single specimen was all that rewarded my labour. Whilst transferring the insect from the net-tube to the bottle for transport, a stranger joined me, and kindly volunteered his assistance. He had no collecting tackle, but in about a quarter of an hour he brought at least a dozen good specimens in the bottle he had borrowed.
It was natural to inquire to what his success was due. He told me that it was his first attempt at collecting, but that just before joining me he had noticed the ends of the breathing-tubes sticking out of the water. This excited his curiosity, and on moving the mud with his walking-stick, the insects were seen to crawl away slowly. When he saw me transfer the Water Scorpion from the net-tube to the bottle, he immediately recognized it. Then he courteously offered his help, for which, of course, I was grateful.
We may keep the Water Scorpion alive for a considerable time in a small bottle of water, in which is some growing weed. If we watch it moving about, we shall see that the front legs are used for locomotion as well as for seizing prey. Some authors doubt this. Any one may settle the question for himself, if he will put one of these insects into a small bottle with plenty of weed. Generally, however, the insect uses only the second and third pairs for walking, the first pair being raised and directed forward, with the tarsus bent at an angle (Fig. 42). Even when it does use its front legs for locomotion, the action is not that of walking; the insect employs these limbs to pull itself along in a sort of ‘hand-over-hand’ fashion, but on a level surface it uses the first pair in the same way as it does the other two pairs.
Its habit of burying itself in the mud may also be watched with very little trouble. A common pudding-basin will make an excellent aquarium for this purpose. The bottom is to be covered with garden mould and vegetable débris, mixed with a few stones. The whole mass should be arranged unevenly, so that when water is added it may not form one sheet, but a series of small shallow pools. Very little duckweed will serve to keep it sweet. It only remains to drop in the Water Scorpion. Before long it will accommodate itself to its new surroundings, and so bury itself that it will be no easy task to discover it.