8G2 



1 N S 



possess winglets, make a buzzing noise. The same 

 is also the case with the bees and other Hymenoptera. 

 Other naturalists have supposed the noise to originate 

 in the motion of the wings themselves, or (with more 

 probability) in the rushing of the air through a spira- 

 cle near the base of the halteres ; in which case, the 

 sole use of the halteres will be as poisers to keep the 

 body steady in flight. Thus Schelver cut off the 

 halteres from a fly, and found that it could no longer 

 fly ; hence (and from other circumstances) he consi- 

 dered that the halteres are connected with respiration. 

 For this reason, apparently, Kirby and Spence have 

 regarded these organs as not being the analogues of 

 the lower pair of wings, but as organs, per se, an 

 opinion likewise maintained by Latreille (Cours. 

 d'Entomol. 241. *). Their insertion upon the meta- 

 thorax, in a position with reference to the metatho- 

 racic spiracle analogous to that of the lower wings of 

 Hymenoptera, together with their occurrence, in an 

 order where only two mesothoracic wings are devel- 

 oped, are reasons amply sufficient to induce us (regard 

 being especially had to the law of relative and pro- 

 portionate development already alluded to, in speaking 

 of the variation in the size of the thoracic segments) 

 to consider the halteres as analogous to the second 

 pair of wings, and not as anomalous appendages. 



f. Psendhalteret (praehalteres, Latreille). We have 

 applied this name to a pair of organs somewhat simi- 

 lar in their construction to the halteres, but placed in 

 front of the wings, in the order Strepsiptera, a fname 

 signifying twisted wings, and proposed by Mr. Kirby 

 for the extraordinary group of bee and wasp parasites ; 

 in allusion to this pair of narrow, elongated, curved, 

 and channelled processes, which (notwithstanding the 

 observation of Mr. F. Bauer, that they were connec- 

 ted with 1t\\e fore-legs,) he regarded as analogous to 

 elytra. Subsequent authors, however, doubted this 

 analogy, and Latreille changed the name of the order 

 to Rlripiptcra. More recent observations have, how- 

 ever, demonstrated that these organs are attached to 

 the mesothorax, which, as well as the prothorax, are 

 extremely short ; and that the large pair of fan-shaped 

 wings are representatives of the lower wings of the 

 Orthoptcra, which are folded longitudinally in a simi- 

 lar manner, although the structure of the thorax is 

 very different. Latreille, however, regards these or- 

 gans as analogous to the mesothoracic tegulae, or 

 basal wing-covers, of the Lejridoplera. He likewise 

 considers them as somewhat analogous to the lateral 

 prolongation of the prothorax, observed in some 

 species of Ptychodce and Scenopinus (Dipterous gen- 

 era). As already observed, however, they have 

 been demonstrated to be the only mesothoracic 

 appendages found to exist in these insects (the wings 

 being metathoracic), consequently they must be re- 

 garded as analogous of the mesothoracic organs of 

 flight. During the short time that these insects pass 

 in the winged state, the pseudhalteres are observed to 

 quiver very intensely. 



2. Legs, or the organ* of terrestrial or aquatic pro- 

 gretsion. If we have found the organs of flight con- 

 structed in a manner totally unlike those of birds, we 

 shall discover equally great differences in the con- 

 struction of their legs. Thus, whilst the former are 

 provided with but a pair of organs for progression on 



Latreille consequently also regards the winglets as the true 

 analogues of the lower wings, although he admits that " ils me 

 semblent neanmoins partir d'un point un peu plus 6\6\ que les 

 ailes." 



EOT. 



the land, winged insects have three pairs, spiders four 

 pairs, crabs five pairs, and centipedes and millipedes 



136 



141 



more than a hundred legs. These organs arise from 

 the sternum of the various segments of the thorax in 

 the true insects, and are employed not only in walk- 

 ing, running, creeping, and climbing, but also in leap- 

 ing and swimming, as well as in various operations 

 connected with their economy. They consist of a 

 series of tubular joints, formed of a similar substance 

 with the remainder of the external parts of the body, 

 and are provided with internal muscles and nerves. 

 The joints have received a series of names analogous 

 to those of the legs of the higher animals. They are 

 the coxa, trochanter, femur, tibia, and tarsus. The 

 coxa (136, a) is the basal joint articulating with the 

 sternum, and very variable in form. The trochanter 

 (136, b] is a very small piece connecting the pre- 

 ceding with the thigh or femur (136, c), which in 

 general is the thickest part of the leg, and in leaping 

 insects greatly thickened, and sometimes toothed be- 

 neath. The next piece is the shank or tibia (136, d], 

 a piece generally somewhat shorter and more slender 

 than the femur, and often gradually thickened to- 

 wards the tip, where it is armed with one or two 

 spurs or spines (calcarea, 136, 1 38, dd], varying in their 

 number and size in adjacent groups. The terminal 

 part of the leg is termed the tarsus (136, <?), divided 

 into several joints, never exceeding five in number, 

 which is always found in the majority of insects 

 with membranous wings, undefended by wing-cases. 

 In many beetles the number is variable, as stated in 

 our article COLEOPTERA, and the same is the case in 

 the Neuroptera, &c. The under surface of these 

 tarsal joints is generally clothed with short hair or 

 down, often forming a kind of cushion or brush ; some- 

 times, also, the underside exhibits several small cir- 

 cular membranous plates or soles (fig. 139, fore tarsus 

 of a Dyticus}. The penultimate joint is also often 

 divided into two lobes, and the terminal joint is also 

 generally terminated by two small bent hooks 

 (ungues, 136, /), between which, in many insects, 

 there are one, two, or three small, often mem- 

 branaceous, appendages, termed pulvilli (fig. 141, 142, 

 143, zzz). In some tetramerous coleopterous insects 

 the penultimate joint is very minute (fig. 140). Messrs. 

 Kirby and Spence regard the fore-legs of insects as 

 arms rather than legs, and accordingly term the ante- 

 rior tarsus the hand, calling the basal joint the planta 

 or palm. That the fore-legs are highly important in 

 performing the economy of the insect cannot be 

 doubted ; they are also often of a very different 



