26 LICE AND THEIR MENACE TO MAN 



garment. In this process not only the outer skin 

 is cast, but also the inside of the mouth with the 

 stabber, and the main tubes of the tracheal 

 system. The insect which emerges is now called 

 a nymph, or sometimes second-stage larva, and 

 is more robust than the first-stage, but is other- 



FIG. 8. CAST SKIN OF BODY- LOUSE. (After Nuttall.) 



1. Eye. 3. Stabber. 



2. Antennae. 4. Claws, incurved to grasp cloth. 



5. Spiracles. 



6. Tracheae. 



wise much like it. At the end of two or three 

 days it moults once more in the same manner 

 and becomes the second-stage nymph or third- 

 stage larva. After the elapse of about three 

 days more it moults for the third and last time, 

 and is now an adult. The adult louse is rather 

 less barrel-shaped than the earlier stages and 

 shows the external evidences of its sex for the 



