INSECT PARASITES AND PREDATORS OF INSECT PESTS 



15* 



gradually becomes weakened by the feeding of the parasite and 

 finally dies. 



Other species of this group may emerge during the spring months, 

 and the adults feed upon the honeydew secreted by aphids and 

 various other insects. Some species, such as the banded digger wasp 

 (Elis quinquecincta Fab.), paralyze their prey permanently, but 

 these seemingly lifeless grubs are seldom encountered, because the 

 parasite female usually buries the grub to a depth of 1 or 2 feet or 

 more before laying the egg upon it. Grubs parasitized by Tiphia, 

 and the cocoons which are formed later, are usually found near the 

 surface of the soil. 



In addition to the wasps mentioned above, a number of parasitic 

 flies attack white grubs. The young maggots are deposited upon 

 the surface of the ground; they then penetrate the soil in search of 

 grubs upon which they may develop. When such a grub is found, 



Figure 10. — Two parasites of white grubs : A, A maggot of the fly Prosena sibirita com- 

 pleting feeding upon a grub; in its earlier stages it fed within the body of the living 

 grub. B, A half-grown larva of the black digger wasp, Tiphia popilliavora, feeding upon 

 a Japanese beetle grub. A, X 4 ; B, X 3. 



the maggot enters the body and feeds upon the juices. The adult 

 flies are found in the field during midsummer. Typical of this 

 group are Microphthalmos disjuncta Wied., which attacks the com- 

 mon white grubs infesting field and pasture lands in the Middle 

 West, and Prosena sibirita (Fab.) (fig. 10, JL), which attacks the 

 grubs of the Japanese beetle. 



EGG PARASITES 



Large numbers of insect eggs are destroyed by minute parasites 

 which develop in them, and some of these egg parasites are so small 

 that nearly 100 may reach maturity in each of the eggs of the larger 

 moths. The adult wasps of these species may measure only one 

 twenty-fifth of an inch or less in length. 



The best known of the species which confine themselves entirely 

 to insect eggs is Trichogramma minutum Riley (fig. 11), which is 

 usually yellowish in the South, nearly black when found in the 



