1907.] Wheeler, The Polymorphum o] AjUs. 13 



smoother thorax, and less prominent scutehum and epinotuni. In colora- 

 tion it is like the Texan species, except that the thorax is less golden above 

 and the mesopleurse are more shining. In the male the petiole is shorter 

 and the tibise are more or less infuscated. The mature pupte of the two 

 species are very readily distinguished by the character of the last pupal 

 envelope. In coloradensis (PI. IV, Figs. 53 and 54) this is pustulate like 

 the semipupal envelope of viridis, the pustules appearing on the abdomen 

 as dilatations in the transverse intersegmental welts above described for 

 viridis. Then, too, the pupal skin of the Colorado species has a series of 

 large pustules extending along the middorsal line of the epinotuni and 

 abdomen and about the front of the pronotum where they are completely 

 absent in viridis. 



0. coloradensis was first noticed August 3, in a colony of S. vaUdiuscula 

 (PI. V, Fig. 68) at Manitou. The ants with their brood were confined in a 

 bottle for the purpose of rearing some of their numerous male and female 

 pupae. The tiny workers were seen to spend much time shampooing an 

 adult female Orasema. Later other females and a few males hatched in the 

 nest and were cared for by the ants like members of their own species. In 

 the course of a few days two of the Orasemoe were found dead on the refuse 

 heap, one having been decapitated and shorn of its legs and wings. This 

 led me to wonder whether the Solenopsis workers which are themselves 

 parasitic and feed on the larvae and pupae of other much larger ants of the 

 genera Formica, Myrmica, Cremastogaster, etc., are quicker than the species 

 of Pheidole to recognize the Orasevice as aliens after they have been reared. 

 August 11, while collecting near Broadmoor, south of Colorado Springs, I 

 found two more infested Solowpsis colonies. This Solenopsis was paler 

 than the form taken at Manitou, and in this respect approached the typical 

 molesta. In one of these colonies I counted twenty pupae and adult Orasemoe. 

 At the same time I noticed that there were very few male and female pupae 

 of the ant. The other colony, which contained nearly as many of the para- 

 sites, was living in cleptobiosis with a large colony of Formica ciliata INIayr. 

 As S. molesta has only one form of worker, and this of minute size compared 

 with the males and females and since, moreover, the males and females of 

 O. coloradensis are of about the same size as the corresponding sexes of the 

 ant, I infer that the larvae of the parasite must feed exclusively on the sexual 

 forms, while the tiny workei's enjoy complete immunity from their attacks. 

 In the same locality in which I saw the Solenopsis nests above described, 

 and on the same day, I found two colonies of Pheidole vinelandica contain- 

 ing the same species of Orasema. One of these colonies was taken alive and 

 placed in a Fielde nest. A careful examination of the worker brood revealed 

 the presence of a single phthisergate with somewhat pigmented eyes and 



