362 



INJURIOUS AND BENEFICIAL INSECTS OP CALIFORNIA. 



of the hosts, the parasites die from lack of food and may be so reduced 

 in numbers that they are not able to check the rapidly increasing num- 

 bers of the hosts and a serious infestation of injurious insects may 



result. On the other hand, 

 many cases are on record 

 where serious outbreaks of 

 insect pests have been 

 brought under control in a 

 marvelous way by these 

 parasites, and in these cases 

 they should be given credit 

 for the great good accom- 

 plished. 



Unfavorable weather con- 

 ditions and the work of 

 secondary parasites are also 

 often responsible for the 

 poor showing of these bene- 

 ficial friends. 



Not all of the insects be- 

 longing to the above super- 

 families are strictly para- 

 sitic upon other animals. 

 Some have become feeders 

 of plant tissues and may be 

 classed as injurious. In this 



Fig. 359. — Soft brown scale, showing exit holes i j.+ .„ _™^ _ , % , v i -j 



of the parasite, Microterys flavus ( How. ) . Greatly l«t ier group may De placed 

 enlarged. (After Quayle, Cal. Agrcl. Exp. Sta.) the clover Seed chalcis and 



the wheat joint-worm, already referred to. The blastophaga feeds in 

 the figs, but is beneficial as a fertilizing agent, which is necessary in 

 the raising of certain varieties of figs. 



