ENEMIES OF PLANT-LICE 105 



The holes were quite inconspicuous, and they were per- 

 ceived only when the wasps entered them. If the openings 

 were as inconspicuous to their enemies as they were to us, 

 there was little need for their closing them. 



None of these wasps seemed to be making burrows. It 

 is possible that these were the holes from which they had 

 originally emerged. We see no reason why they should not 

 serve perfectly well as places of nidification as well. To be 

 sure, the wasps may have dug them before they were dis- 

 covered, but we saw none of them digging at this time. 



On the second day, instead of dancing or digging, all 

 were busy carrying in prey which consisted of aphids, 

 Aphis setariae Thos. [J. J. Davis]. These they carried in 

 their jaws. The wasps clung tightly to their booty, and even 

 when taken in a test-tube and violently shaken they would 

 not release their hold. 



The bank was of "made" or "filled in" ground, with pieces 

 of glass, crockery, cinders, etc., strewn thickly through it, 

 so it was impossible, at this stage, to trace out the delicate 

 burrows to the end; but some that we followed for a dis- 

 tance showed that they were usually very crooked and grad- 

 ually wandered downward in their course. 



From time to time, until the end of September, we visited 

 these tiny black wasps in the dirt bank. While they contin- 

 ued plentiful, they were by no means so abundant as they 

 were on the first day, when they performed the sun-dance. 

 This might have been due to the elimination of the males. 

 The specimens present later and those entering the holes 

 were all the larger ones, probably females, and at no time 

 did we again find the mating behavior ; hence we suspect that 

 X. metathoraticiis mates once for all time. 



Approaching autumn did not seem to cause their industry 

 to wane. On October 6 many of them were out. They 

 were all females, coming and going busily at their nests, 



