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CIRCULAR 3 46, U. S. DEPARTMENT OF AGRICULTURE 



grubs are exposed by plowing during the summer months they are 

 often found to bear larvae of some other insect attached to the body, 

 or the soil cells which they had occupied contain instead brownish- 

 colored, oval cocoons measuring from one-half to 1 inch in length. 

 Only the head and a portion of the skin remain to identify the origi- 

 nal occupant. The insect responsible for the death of the grubs is 

 one of the digger wasps, so called because of their habit of digging 

 burrows in the ground or wood to make nests for their young, or in 

 search of prey. 



As typical of this group Tiphia popilliai-ora Koh. (fig. 9), which 

 attacks the grubs of the Japanese beetle (Popillia japonica Newm.), 



Figure 9. — The adult female of the black digger -wasp Tiphia popiJUavora. X 6. 



may be mentioned. This wasp is jet black, with dusky wings, and 

 measures about two-thirds of an inch in length. It appears in the 

 field late in August and in September, and may be found feeding 

 upon the blossoms of wild carrot, smartweed, and other plants. 

 When the time for egg laying arrives, the female enters the soil in 

 search of grubs, and when one is found it is stung until completely 

 paralyzed and the egg is then laid on the underside of the body. 

 The grub recovers its powers of movement within about half an 

 hour and resumes feeding. The young wasp larva, immediately after 

 hatching, makes a feeding puncture through the skin of the grub 

 and sucks out the body juices. This feeding continues for 2 weeks or 

 more, and during this time the white parasite larva may be seen 

 lying across the abdomen of the grub (fig, 10, B), The beetle grub 



