Mar.,i 9 o8.j Brues : Mutation Among Insects. 49 



partial winglessness associated with elytral anchylosis can hardly he 

 explained through the selection of slight variations, or in fact, by 

 selection of any sort. With this single genus at least, we can scarcely 

 imagine how the small wings can be either an advantage or a detri- 

 ment in any way. It cannot be a matter of the conservation of 

 moisture in the body as has been suggested in connection with certain 

 desert inhabiting Tenebrionidse, since these species of Calosoma seem 

 to be associated indiscriminately with either xerophytic or mesophytic 

 conditions. 



Some other genera of Carabidae contain wingless or subapterous 

 species, but I have not been able to find any which present such con- 

 tinuity as the two just described, although others no doubt exist. 



The Tenebrionid genus Blapstinus affords another interesting case 

 of a small group of beetles which shows a great range of variation in 

 wing development. It is represented in the United States by nearly 

 fifty species, and reaches its highest development in the southwest. 

 The beetles live in common with most members of the family con- 

 cealed beneath stones or bark, some species confined to arid regions, 

 others to the warm and moist regions of the Pacific and Gulf coasts, 

 and some to the more temperate regions of the upper austral and 

 transition zones. 



The great variety of wing development among the species was first 

 noted by Casey in 1890 (Ann. N. Y. Acad. Sci., Vol. 5, p. 416). 

 He found that the wings vary in length from about one fifth to nearly 

 six fifths of the elytral length, and that they are of almost constant 

 shape and size for each species. Regarding their utility, he says : "In 

 no case do they seem to be large enough, however, to give more than 

 a labored and feeble flight." 



In all species except those with the largest wings, the elytra are 

 more or less perfectly anchylosed. 



In a second paper published the following year Casey again refers 

 to the constancy of these organs, as follows : "I have recently by way 

 of experiment dissected a series of eight specimens of a form very near 

 Blapstinus ritfipes, probably a variety or race of that species, and have 

 found a singular and altogether unexpected constancy in the form and 

 size of the rudimentary hind wing, the extreme variation not amount- 

 ing to more than one fifth of the average length, the latter being a little 

 more than one half the total length of the elytra." 



I have been able to examine the wings of a number of species and 



