1000 INSECTS AND AKACHNIDA 



of land and water insects that have a suctorial mouth resembling 

 that of the common bug, the wings of the anterior pair are usually 

 of parchmeiity consistence, though membranous near their tips, and 

 are often so richly coloured as to become very beautiful objects 

 when mounted in balsam and viewed by transmitted light ; this is 

 the case especially with the terrestrial vegetable-feeding kinds, such 

 as the Pentatoma 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 common, 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 

 examples, the wings are beautifully variegated by differences in the 

 depth of that hue. The halteres of the Diptera, which are the re- 

 presentatives of the posterior wings, have been shown by Dr. J. B. 

 Hicks to present a very curious structure, which is found also in 

 the elytra of Coleoptera and in many other situations, consisting in 

 a multitude of vesicular projections of the superficial membrane, to 

 each of which there proceeds a nervous filament, that conies to it 

 through an aperture in the tegumentary wall on which it is seated. 

 Various considerations are stated by Dr. Hicks which lead him to 

 the belief that this apparatus, when developed in the neighbourhood 

 of the spiracles or breathing pores, essentially ministers to the sense 

 of smell, whilst, when developed upon the palpi and other organs in 

 the neighbourhood of the mouth, it ministers to the sense of taste. 1 



Feet. Although the feet of insects are formed pretty much on 

 one general plan, yet that plan is subject to considerable modifica- 

 tions 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 part 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, according 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. 745, 746) ; and 

 these are often serrated (that is, furnished 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, sometimes forming a complete * sole ; ' this is especially the 

 case in the family Gurculionidce ; a pair of the feet of the ' diamond 

 beetle ' mounted so that one shows 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, especially of the fly 

 kind, the foot is furnished with a pair of membranous expansions 



1 See his memoir, ' On a new Organ in Insects,' in Journ. Linn. Soc. vol. i. 1856, 

 p. 136; his 'Further Remarks on the Organs found on the Bases of the Halteres 

 and Wings of Insects,' in Trans. Linn. Soc. xxii. p. 141 ; and his memoir, ' On 

 certain Sensory Organs in Insects hitherto undescribed,' in Trans. Linn. Soc. 

 xxiii. p. 189. , Compare also the interesting memoir of Weinland, in Zeitschr. f. 

 wiss. Zb'ol. li. (18SO>, pp. 35-160, 5 pis. 



2 See, however, Professor Huxley (Anat. of Invertebrate Animals, p. 348), who, 

 regarding the 'pulvillus' of the cockroach as a joint, finds the number to be six. 



