50 Journal New York Entomological Society. [Vol. xvi. 



have found that they agree with the measurements given by Casey, and 

 to be very constant in the same species, so far as I can determine from 

 the small series of each. 



If these organs in Blapstinus are of no use for the primary function 

 of flight, and are adapted to no secondary use, it would seem that we 

 must look elsewhere than toward natural selection for the explanation 

 of their origin and maintenance in so many and such constant degrees 

 of degeneration among various species. As we have seen in the sev- 

 eral groups previously discussed, this genus forms a very compact series 

 separable only by minute specific differences which are apparently not 

 or very slightly correlated with the variations in the wings. 



The abundance of wingless beetles in arid regions has led me in 

 this case to examine rather closely the geographical range and habitat 

 of the various species so far as they have been recorded. I have been 

 unable, however, to detect any positive connection between wing-length 

 and environment with the exception of an apparent, but slight tend- 

 ency toward smaller wings in desert or dry regions and longer ones 

 in moist or cooler regions. Species with long, and others with very 

 short wings often have overlapping or nearly coincident ranges in both 

 humid and dry regions, but as has been found among other groups of 

 Tenebrionidse, the distinctly northern or northeastern species have the 

 wings comparatively well developed. 



That we have here another case not explainable by natural selection 

 alone, I strongly suspect, while the acceptance of mutation will give 

 at least a plausible explanation of the conditions as we find them. 



The species belonging to the Hymenoptera are among the most 

 active forms of insect life, yet we find two large and very many smaller 

 groups where the wings of one sex are regularly absent or more or less 

 atrophied. The more interesting cases from our present standpoint 

 are to be found in the normally winged large groups where certain 

 genera are regularly wingless. 



In the Hymenoptera the wings whenever present, even as vestiges, 

 are always entirely external, and never permanently concealed as 

 among the Coleoptera heretofore considered, so that we must be 

 extremely careful in assuming that they can ever be entirely without 

 selective value. Nevertheless the occurrence in precisely similar 

 environments of fully winged and partially or completely apterous 

 species is not at all rare. A genus of small parasitic Hymenoptera, 

 Megaspilus, is well represented in this country by a number of winged 



