12 DESCRIPTION OF PARTS. 



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

 gingHmus (articulation) : it i- so formed that it maj be closely applied to the thigh. Spines 



and spars are also found upon the tibia or shank : when the spines are short, they are 

 regarded a- teeth. The spun BIS articulated With the part, and pox-ess some motion : they 



are commonlj arranged in pairs at the extremity of each tibia. 



The tibia terminates below in the tara%s } 01 l'<><>t : this consists of a mi ie-of pieces, more 

 or less heart-shaped] and never exceeding five in number. The combined motion of these 

 pieces i- considerable, though it is such as belongs to the ginghmus articulation : they are 

 never of equal length, ami the lir-t one j- the longest of all. The terminal piece hears a 

 hind claw, often dentate or serrate on the edges; and a spurious claw is frequently found 

 between the branched In addition to the forenamed parts, we often find cushions placed 

 upon the bottom ol' the foot, which serve as sucking cups, enabling the insect to support 

 itself in a pendant position. Hair- 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 ease that the hindlegs have a form specially adapted to a particular 

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



The third part of the bodj 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 

 one- \ -. . tioH of the abdomen exhibit- 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 e<pui| to that of the first segment ; in other cases the onion 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 

 lir-t, the interior and middle parts are joined or soldered together, leaving the sides and 

 dorsal portion- 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 greate-t freedom exists in 

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

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



The abdomen, being comparatively free, i- well fitted to sustain the function of respira- 

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

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

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

 is devoted t. • digestion, and is also the cavity in which the generative organs are lodged, it 



