4 io ECONOMIC ZOOLOGY AND ENTOMOLOGY 



The most extensive experiment in attempting to control a 

 serious insect pest by its insect enemies is the work that is now 



FIG. 194. FIG. 195. 



FIG. 194. Aphids on a leaf, which have been parasitized by a Braconid 

 parasite. (About natural size.) 



FIG. 195. Larvas and pupae of the oak tree moth, Phryganidia califor- 

 nica, that have been killed by a disease caused by bacteria. (Natural 

 size.) 



being carried on by the Bureau of Entomology in the fight 

 against the gipsy-moth in the New England states. The way 



