154 C - H> TURNER. 



On the nearly level, but slightly higher, land about the head- 

 waters of this brooklet, on the 26th of August, 1921, three colonies 

 of Odynerus dorsalis were discovered (Fig. i, B, a, c, c). One of 

 these (Fig. i, A) was on a spot that was absolutely barren; the 

 other two were in spots the barrenness of which was partly inter- 

 rupted by low-growing weeds (Fig. i, C). At no other place in 

 that desert strip, nor on any of the land for a half mile around, 

 were there any colonies of this species. There, and at no other 

 place in the neighborhood, were found the three essentials for the 

 existence of this species : a patch of hard, dry, land, a near-by body 

 of water, and a field infested with Hesperid caterpillars. 



Evidently such a locality a barren, or nearly barren, patch of 

 dry, hard, ground, near-by water, accessible Hesperid larvae is the 

 normal habitat of this species, for it is in just such situations that 

 it has been found by Isely ('14, p. 282) and by the Raus ('18, 

 p. 312). Hartman's statement ('05) that the species constructs 

 mud nests on grass stems is the only discordant note in the litera- 

 ture, but his experience is radically so different from that of Isely, 

 the Raus, and me that it is hard to believe that he is discussing the 

 same species. Indeed, in a letter to Mr. Rau, Hartman states that 

 it is probable that the species he discusses had been wrongly 

 classified. 



If one thinks in terms of social bees and hornets, the word popu- 

 lous could hardly be applied to these colonies ; but they were 

 slightly larger than those seen by Isely. Isely ('14, p. 293) writes : 

 " 0. dorsalis has a tendency to nest in colonies. I sometimes found 

 an isolated nest, but usually the nests were in small groups, some- 

 times as many as eight. Usually only two or three wasps would 

 share an open space in a pasture, each wasp digging one or two 

 nests. I never found them in populous colonies like those of 

 O. papagoruin." In speaking of O. papagorum, he says (op. cit., 

 p. 256) : "Hundreds of them were at work there in the high banks 

 of light earth." In the three colonies observed by me the number 

 of wasps varied from twelve to sixteen. This estimate was made 

 not by counting the wasps, but by noting the number of holes that 

 were in process of construction or of being provisioned at the 

 same time. 



