ISELY: EUMENID^ OF KANSAS. 291 



species of this genus, very stout, being larger near the anal end, 

 and whitish in color. 



The last of the pupal stage I had opportunity to observe in 

 the bank colony of nests. Two pupa;, almost ready to disclose 

 wasps, were taken from the lower two cells in a gallery of 

 four. In another nest in the lowest cell another pupa was 

 taken. The rest of the nests were empty. I placed these pupae 

 in glass vials. One disclosed the next day and the other two 

 disclosed on the third day after I had taken them. All were 

 females. These pupae were colored almost like the adults, ex- 

 cept that the rufous on the abdomen was lighter, and the yel- 

 low ornaments were pallid. All were resting on the tips of 

 their abdomens, with their heads upward. 



My attention was attracted to the location of the bank colony 

 by a number of males of 0. dovsalis which collected on the face 

 of the bank around openings to these nests from which wasps 

 had emerged. Occasionally one of the males would inspect 

 the entrance of all the open burrows in the bank. At two of 

 the burrows these males always stopped to put in their heads, 

 and sometimes one would enter part way. While he would fly 

 to the others in the course of his circuit, Mr. Wasp would stop 

 at them only momentarily, and then take wing again. The 

 two burrows in which the males manifested such a special in- 

 terest proved to be the ones which contained the female pupae 

 nearly ready to be disclosed. 



These males were very quarrelsome. Often when one would 

 put his head into the burrow another would dash at it, and 

 together they would fall to the base of the cliff. Occasionally 

 they would dash at each other without any evident provocation. 



From the fact that only females were found in the lower cells 

 of these nests, and that males were waiting apparently for 

 their emergence at the mouths of the burrows, I should judge 

 that males emerge first, as in the case of others of this genus. 

 Perhaps the upper cells of the galleries, which were empty, 

 had contained these males. 



In a number of the empty cells of this colony I found heads of 

 caterpillars, probably hesperids, evidently discarded by the 

 wasp grub. 



0. dorsalis had an abundance of insect enemies. The find- 

 ings in the cells of the bank colony may suggest the extent to 

 which other insects interfere with their increase of numbers. 



