15^ W. M. WHEELER AND J. F. McCLENDON. 



find cross-fertilization by males of their own species from other 

 nests very difficult and fertilization by males of clai'igcr a rela- 

 tively easy matter. 



(K) The nuptial flights of the two species may occur simul- 

 taneously. In fact, the senior author witnessed a flight of clai'igcr 

 from a nest not twenty feet away from the latipcs nest and at the 

 very same time (3.30 P. M.) as the above-described flight of the 

 latter species. And it may also be stated that both these nests 

 were large and must therefore have existed side by side for some 

 years. We could suppose that a /3-female of latipcs in some 

 previous year had been fertilized during her nuptial flight by a 

 male clai'igcr and had returned into the parental nest to give 

 birth to the ^-females which celebrated their nuptial flight on the 

 1 7th of September, 1902. 



() This view is also supported by the fact that the -female is 

 so clearly intermediate in nearly all its characters between the 

 female clai'igcr and the ^-female, as has been shown in the above 

 tables. 



The arguments that can be brought to bear against the hy- 

 pothesis are the following : 



(a) We have failed to find any hybrid workers in the nests 

 containing the - and /9-females. This should be the case un- 

 less we suppose that all the hybridized /9-females produced only 

 queens. 1 But it must be borne in mind that the hybrid between the 

 worker clavigcr and worker latipcs would differ presumably from 

 the parent species only in intermediate pilosity and in having a pet- 

 iole intermediate in shape. Such differences would not be easily 

 detected, as anybody will confess who has examined a large series 

 of workers of the two species. The workers are of small size 

 and the petiole is sometimes decidedly variable even within the 

 limits of the same species of Lasins. 



(t)] It is improbable that hybridization could occur so fre- 

 quently in a state of nature as appears to be indicated by the 

 high percentage of nests containing r/.-females, and their occur- 

 rence in such widely separated localities. If we are really con- 

 fronted by a case of hybridism we are almost compelled to believe 



1 Obviously the male offspring of the hybridized queen would not he affected, 

 since they arise from unfertilized eggs. 



