576 INSECTS AND ARACHNIDA. 



is possessed by most insects of this order, and especially by the 

 common House- Or icket ; this consists of the "tympanum" or 

 drum, which is a space on each of the upper wings, scarcely 

 crossed by veins, but bounded externally by a large dark vein 

 provided with three or four longitudinal ridges, and of the "file" 

 or "bow," which is a transverse horny ridge in front of the tym-_ 

 panum, furnished with numerous teeth ; and it is believed that' 

 the sound is produced by the rubbing of the two bows across 

 each other, while its intensity is increased by the sounding-board 

 action of the tympanum. The wings of the Fulgoridce (lantern- 

 flies) have much the same texture with those of the Orthoptera, 

 and possess about the same value as microscopic objects ; differ- 

 ing considerably from the purely membranous wings of the Ci- 

 cadse and Aphides, which are associated with them in the order 

 Homoptera. In the order Hemiptera, to which belong various 

 kinds of land and water insects that have a suctorial mouth re- 

 sembling that of the common Bug, the wings of the anterior pair 

 are usually of parchmenty consistence, though membranous near 

 their tips, and are often so richly colored as to become very beau- 

 tiful objects, when mounted in balsam and viewed by transmitted 

 light ; this is the case especially with the terrestrial vegetable- 

 feeding kinds, such as the Pentato?na and its allies, some of the 

 tropical forms of which rival the most brilliant of the Beetles. 

 The British species are by no means so interesting; and the 

 aquatic kinds, which, next to the bed-bugs, are the most com- 

 mon, always have a dull brown or almost black hue ; even among 

 these last, however, — of which the Notonecta (water-boatman) and 

 the Nepa (water-scorpion) are well-known forms, — the wings are 

 beautifully variegated by differences in the depth of that hue. 



397. Feet. — Although the feet of Insects are formed pretty 

 much on one general plan, yet that plan is subject to considerable 

 modifications, in accordance with the habits of life of different 

 species. The entire limb usually consists of five divisions, namely, 

 the coxa or hip, the trochanter, the femur or thigh, the tibia or 

 shank, and the tarsus or foot ; and this last portion is made up 

 of several successive joints. The typical number of these joints 

 seems to be five ; but that number is subject to reduction ; and 

 the vast order Coleoptera is subdivided into primary groups, ac- 

 cording as the tarsus consists of five, four, or three segments. 

 The last joint of the tarsus is usually furnished with a pair of 

 strong hooks or claws (Figs. 294, 295) ; and these are often ser- 

 rated (that is, fhrnished with saw-like teeth), especially near the 

 base. The under surface of the other joints is frequently beset 

 with tufts of hairs, which are arranged in various modes, some- 

 times forming a complete " sole ;" this is especially the case in 

 the family Ourculionidce ; so that a pair of the feet of the "dia- 

 mond-beetle," mounted so that one shoAvs the upper surface made 

 resplendent by its jewel-like scales, and the other the hairy 

 cushion beneath, is a very interesting object. In many Insects, 



