SOME WINGLESS INSECTS 



171 



the last stage but one, the new cuticle of mandible and of the 

 beautiful and delicate extremities of the adult's maxilla can 

 be clearly seen (Fig. 97 B, F) beneath the old cuticle now worn 

 down by use. 



The other considerable order of the Apterygota are the 

 Collembola or spring-tails. These (Fig. 98) are curiously 

 modified insects, with short feelers (usually four segments only), 

 no compound eyes but a group of (usually eight) ocelli on each 

 side of the head, the mouth region inpushed so that the jaws 

 appear to be retracted into the head, only six abdominal 



FIG. 98. SPRING-TAIL (Cryptopygus crassus), GRAHAMLAND, ANTARCTICA. 

 a, adult (side view) ; b, young specimen, x 25. c, mandible ; d, e, /,, three 

 stages in growth of spring. xi6o. After Carpenter, Proc. R. Soc. Edinb. 

 XXVI). 



segments, the first of which has its appendages modified into 

 an adhesive ventral tube, while the limbs of the third and 

 fourth are respectively specialized as a minute pincer-like 

 toothed "catch" (Fig. 99 a), and a more or less elongate 

 " spring", which consists of a basal median piece (manubrium) to 

 which are jointed a pair of processes (denies) usually flexible, 

 each terminating in a toothed claw (mucro). This spring can be 

 held directed forwards beneath the body by the catch which 

 grips the manubrium between the two dentes. When the 

 catch releases the manubrium, and the extensor muscles of 

 the spring contract, the spring is pulled strongly downwards 

 and backwards so as to strike the ground and the insect jumps 

 into the air for a distance that may be described as enormous, 

 as compared with its own size. 



