PARASITISM AND DEGENERATION 



195 



itself to some stone or shell, or pile or ship's bottom, loses 

 its compound eyes and feelers, develops a protecting shell, 

 and gives up all power of locomotion. Its swimming feet 

 become changed into grasping organs, and it loses most of 

 its outward resemblances to the other members of its class 

 (Fig. 123, e). 



FIG. 123. Three adult crustaceans and their larvae, a, prawn (Peneus), active and 

 free-living ; b, larva of prawn ; c, Sacculina, parasite ; d, larva of Sacculina ; 

 e, barnacle (Lepas), with fixed quiescent life ; f, larva of barnacle. After 

 HAECKBL. 



Certain insects live sedentary or fixed lives. All the 

 members of the family of scale insects (Coccidae), in one 

 sex at least, show degeneration, that has been caused by 

 quiescence. One of these coccids, called the red orange 

 scale (Fig. 124), is very abundant in Florida and California 

 and in other orange-growing regions. The male is a beau- 

 tiful, tiny, two-winged midge, but the female is a wingless, 



