ENEMIES OF PLANT-LICE 



103 



FIG. 27. The clay bank where Xylocelia mctaihoracicus build their 

 burrows. 



time, in the same manner as Bcmbi.v and other wasps, to 

 participate in a sun-dance at the opening of their season of 

 activity. 



They did not wander far from the general region ; neither 

 did they keep in a strictly defined swarm as some insects 

 do, but wavered lightly and leisurely to and fro in front of 

 the face of the bank. As they hovered and flew they 

 always kept their heads toward the wall. Occasionally they 

 sat down at the foot of the bank to rest and rub their abdo- 

 mens. Frequently, while one was resting thus, another 

 dashed down and bumped against it, or pounced upon it 

 and stirred it into flight again. Only twice on these occa- 

 sions did we see real matings accomplished. One mated pair 

 on the wing was soon lost to view; the other remained in 

 copulo, the male surmounting the female, for five minutes 

 before we lost sight of them. The pairs seemed to be 

 equally at ease walking, resting or flying. While at rest, 



