304 KANSAS UNIVERSITY SCIENCE BULLETIN. 



species as observed by Mr. Hartman. When he pulled up the 

 grass before her nest she was disturbed only for the moment. 

 Neither 0. papagorum nor 0. dor sails objected to being ob- 

 served. 



0. annulatus was sensitive even to my presence in the 

 vicinity of her nest, and sometimes delayed work because of it. 

 None of these species were as extreme in sensitiveness as 

 0. vagus, mentioned by the Peckhams, which delayed work for 

 half an hour because of a red match head within two inches of 

 her burrow. 



It was interesting to me to note that 0. annulatus, which 

 seemed to be the most plastic in habits of all the species I ob- 

 served, was also apparently the best observer. 0. papagorum, 

 whose habits seemed inflexible, at least in the choice of a nest- 

 ing site, appeared to be a very poor observer. 



A fact that greatly impressed me in my study, and that 

 sometimes astonished me, was the variability in habits exhib- 

 ited by members of this family. I had expected the different 

 species of the family to differ from each other, but a wide 

 variation was often exhibited by members of a species. 



Within the species O. annulatus I found one lazy individual 

 that used a vacated mud dauber's nest as her storehouse; an- 

 other individual of the same species laboriously excavated a 

 twenty-two-celled nest in the hardest of clay. The variation 

 among individuals of 0. dorsalis is not less striking. I was 

 surprised when I found that this wasp dug its nest in two situ- 

 ations, as either in the side of a bank or in level ground. My 

 surprise grew to astonishment when I read Mr. Hartman's 

 account, stating that 0. dorsalis also constructs cells above the 

 ground. O. arvensis, too, varies widely in its choice of nesting 

 sites ; I found her to be a burrower in various situations, while 

 Mr. Hartman credits her with building in convenient holes and 

 crevices. 



As far as I observed, 0. papagorum is in many ways a dis- 

 senter from this rule of variation, at least in regard to nesting 

 sites and the type of nest used. She appeared to have but one 

 favored nesting site, and that was limited by a number of con- 

 ditions. I believe her to be less plastic also in her other habits 

 than the species mentioned. Yet within this most stable 

 species variations were on every hand. For instance, consider 

 the cells, their variability in number in a nest, in arrangement, 

 and in the direction of their long axes. Or consider excep- 



