BEHAVIOR OF POMPILID WASPS 89 



group of identical cells was found under a plank which 

 covered a depression in the ground. Both lots, however, 



FIG. 20 B. A mud nest of Pscudagenia mellipcs within an oak-apple. 

 Slightly enlarged. 



gave us not Pscudagenia wasps, but both sexes of the para- 

 sitic cow-killer, Sphaerophthalma scaeva Blake [S. A. 

 Rohwer] . 



