Aug. 15, 1884.] 



♦ KNOAVLEDGE 



135 



stance to a much smaller bulk, and rendering it innocuous 

 to a degree that might at first seem impossible. Halt 

 buried in this mud, or slowly crawling over its surface, are 

 the lurking monsters of entomological pond life, the 

 majority of which belong to two orders we have hitherto 

 scarcely noticed, the Neuroptera and Trichoptera, the 

 former containing the dragon flies, and the latter the 

 caddis flies. We will, however, first consider certain bugs 

 which haunt these parts. 



They are known as water scorpions, and two species 

 inhabit this country, one commonly found in almost every 

 pond, the other of much less frequent occurrence. They 

 have, of course, no connection with the true scorpions, 

 which are not insects at all, but eight-legged creatures 

 belonging to the class containing spiders and mites. The 

 water scorpions, too, unlike their terrestrial namesakes, are 

 not venomous. The first, and much the less common, is 



Fig. 1. — Eanatra linearis (reduced). 



a long, narrow insect, called Ranatra linearis (Fig. 1). On 

 account of its habit of frequently lurking in an inclined 

 position amongst the water weeds, often only a little below 

 the surface, this creature belongs less to the fauna of the 

 bottom than its common relative. Still, they are best 

 treated of together. It is of a brownish colour, except 

 the upper surface of the abdomen, which is scarlet, but 

 this is concealed when the insect is in the water, being 

 made apparent only when the wings are expanded, and 

 then it is quite astonishing to see what a beautiful creature 

 the apparently uninteresting object becomes. The head is 

 small, but the eyes exceedingly prominent, as is often the 

 case with aquatic insects, and the beak short and sharp, 

 not bent underneath, but projecting in front like an ex- 

 tremely acute nose. Both thorax and abdomen are elon- 

 gated to an enormous extent ; indeed, the insect, with a 

 length of an inch and a- half from tip of snout to end of 

 abdomen, has its greatest breadth no more than one-sixth 

 of an inch. The upper pair of wings, whDe almost 

 abdomen, are each only about 

 but the hinder pair are con- 

 and have to be carefully folded 

 be stowed away under their narrow 

 covers. These hind wings are beautifully delicate and 

 transparent, similar, indeed, to those of the Corixidae 

 before referred to. But when we have reached the tip of 

 the abdomen, we have by no means got to the end of the 

 insect ; from this point there extend two long bristle-like 

 organs, about an inch in length, which project straight 

 behind like a stiff tail ; they are tubular, and communicate 



as long as the 

 half its width, 

 siderably broader, 

 up before they can 



at their base with the tracheal system, and are, of course, 

 respiratory in function. The legs are long and slender ; 

 the first pair are not used for progression, but for seizing 

 prey, and it is these in front, and the respiratory filaments 

 behind, that give the creature whatever resemblance it 

 may have to a scorpion, although the similarity to that 

 venomous animal is not nearly so exact as in the other 

 species to be considered presently. The front legs are 

 most remarkable objects, and will well repay a careful 

 study. To understand clearly their peculiarities, we must 

 first refer to the general plan of an insect's leg (Fig. 2). 



Fig. 2. — (A) Fore-leg of Eanatra ; (B) Leg of Stag-beet'e. 

 a. Coxa ; i. Trochanter ; c. Femur ; d. Tibia ; e. Tarsus, 



There is first a joint, usually comparatively small, and 

 more or less globular, called the coxa, by which the leg is 

 articulated to the body, and which is usually invisible from 

 above. Succeeding this is a small triangular joint, called 

 the trochanter, squeezed in, as it were, between the coxa 

 and the next joint, and looking as if added, as an after- 

 thought, to fill up a gap. Then follows, attached to the side 

 of the trochanter, the first long piece of the leg, the thigh, 

 or femur, then another long piece, the shank, or tibia, and 

 lastly the tarsus, or foot, which is composed of from two 

 to five joints, and usually terminated by a pair of claws. 



Now let us take one of Ranatra's fore-legs and compare 

 it with this plan. First we find a long joint, which extends 

 far beyond the head, but still, from its being that which 

 articulates the leg to the thorax, we know it must be the 

 coxa, though it protrudes so far that we may easily at first 

 mistake it for the thigh. Then there is the trochanter, a 

 little larger and more conspicuous than usual, and this is 

 succeeded by a long piece slightly curved at the further 

 end, and with a tooth a little beyond the middle ; this, of 

 course, is the femur. After this there is a short, sickle- 

 shaped part, less than half the length of the femur, and 

 looking like a great claw ; it is able to be folded back upon 

 the inner edge of the femur, along which a narrow groove, 

 serrated at the edges, is excavated to receive it, and then 

 its tip just reaches the above-named tooth. This sickle- 

 shaped part consists of both tibia and tarstis, the latter of 

 which is very small and has no claws. It will thus appear 

 that the leg proper is, as it were, spliced on to the end of a 

 long handle, the elongated coxa, an arrangement the efiect 

 of which is to give the limb much greater freedom of 

 motion and a much wider sweep, and thus to enable it to 

 levy tribute over a much more extended area. So peculiar 

 is the plan of these Limbs that it is no wonder that many 

 persons have been puzzled to understand them. 



We must leave the habits of Ranatra for consideration 

 in the next paper. 



(To be continued.) 



The Fkexch Eiectrical Power Stoeace Cojipaxt. — Yice-Chan- 

 cellor Bacon made an order on Saturday week for the winding-up 

 of this Company on the petition of the Faure Electric Accumulator 

 Company. It was stated in court that the proceeding was rendered 

 necessary by the frauds of M. Phillippart, whose name has been so 

 intimateh- associated with electric lightning and accumulatoi-s. 



