13 DESCRIPTION OF PARTS. 



akBder than the thigh, and is connected with it by a joint similar to a knee-joint, culled 

 gtmgUmm* (articulation) : it is so formed that it may be closely applied to the thigh. Spines 

 •nd spurs are also found upon the tibia or shank : when the spines are short, they are 

 MUded as teeth. The spurs are articulate<l with the part, and possess some motion : they 

 ate commonly arranged in pairs at the extremity of each tibia. 



The tibia terminates l)elow in the tarsus, or foot : this consists of a series of pieces, more 

 or less heart-shai)ed, and never exceeding Ave in number. The combined motion of these 

 pieces is considerable, though it is such as belongs to the ginglimus articulation : they are 

 never of equal length, and the first one is the longest of all. The terminal piece bears a 

 bifid claw, often <lcntate or serrate on the edges ; and a spmious claw is frequently found 

 between the branches. In addition to the forenamed parts, we often And cushions placed 

 upon the bottom of the foot, which serve as sucking cups, enabling tKe insect to support 

 itself in a pendant position. Hairs also clothe the sole. 



The forelegs often exhibit a form more or less divergent from the others, and hence serve 

 an additional purpose in the economy of the insect : they are employed in prehension. 

 So it is sometimes the case that the hindlegs have a form specially adapted to a particular 

 purpose, such as the rolling of the ball in which the eggs are enclosed, etc. 



The third part of the body of an insect, which calls for our attention, is the abdomen : 

 it has no appendage, and in this respect differs from the parts already noticed. Its external 

 structure is not peculiar ; for, like the other parts, it is composed of a scries of horny rings 

 or segments, which are closely connected together. The rings do not exceed nine in num- 

 ber ; if they appear to be fewer than nine, it may arise from the overlapping of adjacent 

 enes. A «ection of the abdomen exhibits a triangular outline. The abdomen itself is united 

 to the thorax, but not always in the same way : the area of junction is sometimes broad, 

 or equal to that of the first segment ; in other cases the union is by a short stem, or petiole, 

 consisting of a trumpet-shaped tube : the abdomen is sessile in the former case, and pe- 

 tiolated in the latter. The rings or segments are united to each other in two ways : by the 

 first, the inferior and middle parts are joined or soldered together, leaving the sides and 

 dorsal portions only free ; by the second way, there is no soldering of parts, but the rings 

 are supported by overlapping each other, and may slide into each other like the pieces of 

 a telescope. In the former mode, motion is restricted, while the greatest freedom exists in 

 tlie latter. The segments are lined by a membrane, but it is scarcely visible except in the 

 ease of a gravid female, when it is seen distended like a bag. 



The abdomen, being comparatively IVee, is well fitted to sustain the function of respira- 

 tion. To this end, each segment or ring is furnished with an opening for the transmission 

 of air, which penetrates thence in appropriate vessels throughout the whole body. These 

 openings are surrounded by rings, and are usually denominated spiracles. As the abdomen 

 is devoted to digestion, and is also the cavity in which the generative organs are lodged, it 



