Ecological and Behavior Notes 37 



of this species about the middle of July. Tlie interior 

 of this twig gave every evidence of being, or at one time 

 having been, the property of a Ceratina bee, but I could 

 not discover whether or not P. cressoni was a parasite 

 on Ceratina, or merely an occupant of her abandoned 

 dwelling. 



Colletes compactus Cress. [J. C. Crawford]. We have 

 described the courtship and mating habits of this species* 

 on a bright September afternoon. I was so fortunate as 

 again to meet this species, on September 17 and October 

 3, 1917, on a sandbar in the Mississippi River at Wickes. 

 They were abundant on both of these occasions. Identi- 

 fication by Mr. J. C. Crawford showed that the first lot 

 collected contained some males of Colletes willistonii. 

 Associated with the bees in great numbers was the beetle, 

 Cicindela rapanda De Jean [E. A. Schwarz]. The court- 

 ship behavior witnessed on October 3 was just as exciting 

 as the sun-dance observed a few years ago, despite the 

 fact that the weather was dark and gloomy. Hence it 

 seems that the courtship is not influenced by the sun- 

 light, since a more sunless and dreary day could hardly 

 be imagined than the last. Furthermore, the sandy area 

 upon which their activities occurred was thoroughly 

 moist. Hundreds came from their mysterious hiding- 

 places to dance over an area about three feet in diameter. 

 All were in a great state of excitement, weaving in and 

 out in the air, in the limited space and never higher than 

 two or three inches from the ground. When one of them 

 stopped to rest, others were soon on top of it. All ap- 

 peared from their size to be males, and there was no sign 

 of mating. Once a drowsy Polistes annularis happened 

 to alight in their midst; at once several male Colletes 

 alighted on her back, and one actually attempted to mate. 

 The Cicindela beetles which were watchers on the out- 

 skirts of the dance area often slowly crept into the ring 



•Journ. Animal Behavior 6:367-370, 1916. 



