206 



APPLIED ENTOMOLOGY 



louse (Fig. 199) and, facing it, will thrust its abdomen forward beneath 

 its body and drive its ovipositor into the louse. The young parasite 

 hatching from an egg thus deposited, will feed upon 

 the aphid whose body becomes distended and 

 generally changes color after a time and finally 

 dies adhering to the plant on which it was. When 

 the parasite has completed its development within 

 the body of the louse it escapes by cutting a 

 circular, lid-like opening through the skin (Fig. 200), 

 and lice attacked and killed in this way are often 

 very plentiful during and particularly toward the 

 end of a period of destructive abundance of these 

 insects (see page 344). 



Family Aleyrodidae. The adults of the insects 

 belonging in this family (Fig. 201) are very small 

 and have four wings which are broadly rounded 

 and have a white dust covering them, which has 

 led to calling the group the White Flies. Occa- 

 sionally the wings have dark spots or streaks. The 

 eyes are often constricted in the middle or even 

 divided into two parts. The body is generally 

 yellowish, though in some species it may be of 

 other colors. 



The nymph on hatching, crawls around for a 

 short time before settling down on a leaf, then in- 

 serts its rostrum in the tissues and begins to feed. 



After molting the insect becomes quiet, with its legs and antennae much 

 reduced, and thereafter does not move from its location until it becomes 



FIG. 200. Plant Lice 

 killed by parasites. Up- 

 per figure shows the 

 circular piece of chitin 

 cut by the parasite in 

 escaping, but still at- 

 tached. Lower figure 

 shows the parasite just 

 escaping. Much en- 

 larged. (From U. S. D. 

 A. Bur. Ent. Bull. 110.) 



FIG. 201. Adult White Flies twice natural size. (From Britton, Second Report Ent. Conn. 



Agr. Exp. Sta. 1902.) 



adult, and wax which may have been produced before the first molt, 

 now becomes more noticeable. This wax may take the form of a fringe 



