THE BED-BUG 



291 



adult. The operation is effected in the same^way as in the 

 cockroach, viz., by the splitting of the skin along a straight 

 line down the middle of the back in the region of the 

 thorax, and the whole animal gradually extricates itself 

 at this aperture, carefully removing not merely the more 

 robust parts of the body from their covering, but neatly 

 withdrawing also the more slender parts, such as the 

 legs and antennas, each 

 separately from its 

 own sheath. During 

 the moult, the claws 

 at the tips of the tarsi 

 are useful in obtain- 

 ing a foothold on the 

 irregularities of the 

 wood, paper, &c., on 

 which the change 

 takes place; by this 

 means the shells of 

 the limbs are pre- 

 vented from becoming 

 crushed and collapsed, 

 and are enabled to 

 retain their proper forms ; hence, but for the distortion 

 caused by the fracture along the back, and the paler 

 tint, the cast skin (Fig. 97) might easily be mistaken 

 for the insect itself. 



The last moult but one introduces the form usually 

 called the nymph (Fig. 98), which corresponds to the 

 chrysalis of those insects whose metamorphosis is com- 

 plete. As the bug grows with each moult, its colour 

 deepens, and its skin becomes harder and less flexible, so 

 that when it has reached the nymph stage it closely 

 resembles the adult, though still rather smaller. The 



FIG. 97. The Cast Skirf of an Adult Bug, 

 seen from above. 



