CHAPTER IV 

 THE ENEMIES OF THE PLANT-LICE 



Xylocelia metathoracicus 1 Mickel. [S. A. Rohwer]. 



The picture herewith (fig. 27) will give the reader an 

 idea of the physical features of the site of the only colony 

 of Xylocelia mctathoracicus which we have observed. This 

 perpendicular bank, six feet high, was the side of a gully 

 which had been washed through a vacant lot by many rains. 

 The wall at this point faced directly southward, where the 

 sun beat down with burning glare, and not a breath of 

 breeze could enter the hole walled in by dirt and tall vege- 

 tation. 



On September 3 we came here in quest of large game, but 

 found instead a swarm of these tiny black wasps dancing 

 in the sun on the face of the bluff. We were startled to find 

 them here in so great numbers, for none had been in evi- 

 dence when we had visited the place only the week before. 

 At that earlier date, however, in digging out a Philanthus 

 burrow in this same bank, we had exhumed a tiny cocoon 

 from which emerged one of the X. metathoracicus, the first 

 we had ever seen. This one incident leads us to think that 

 the normal time of emergence of these wasps was Septem- 

 ber i, and that the entire population had come forth at this 



1 This wasp has been only recently described by Mickel, Ann. Ent. 

 Soc. Amer. 9: 3/19. 1916. Mr. Rohwer writes that Xylocelia is the cor- 

 rect name for Diodontus in the Pemphredonini as treated by Fox. 



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