22 NORTH AMERICAN ACRIDIID^E. 



be it sub-alpine or sub-tropical, in forest or swamp or in burrows, 

 crevices, etc. in short, in stations where wings are not needed or 

 are at a disadvantage, are very generally apterous or brachypterous. 

 Brachypterism, therefore, appears to be largely not so much 

 a case of natural selection through the agency of the wind as an 

 adaptation in structure to habits. The fact that the heavier-bodied 

 female is more frequently or completely brachypterous than the 

 male and that the tegmina in the latter sex when used as musical 

 instruments are retained in a less degenerate condition (even when 

 entirely useless in flight), confirms this explanation of brachypterism. 



"BURNING OVER" AS A FACTOR IN DISTRIBUTION. 



A factor which must seriously affect the distribution of some 

 species is the widespread custom of " burning over" the mountains 

 to improve the range for stock. This practice results necessarily in 

 the destruction of much of the woody de*bris lying upon the ground 

 which is used as a nidus for the eggs by Chloealtis conspersa, a short- 

 winged boreal species of wide distribution in the Northern States, 

 where it is plentiful in numbers even on the offshore islands. A 

 very few examples of this species were found at high elevations in 

 the mountains of western North Carolina and Virginia, and it would 

 seem not unlikely that the custom referred to may be largely 

 responsible for its scarcity in that region. Since the burning is 

 usually done during the winter, or at least in the inactive season of 

 locust life, it would affect a species having the habit of oviposition 

 mentioned more injuriously than one ovipositing in the earth. 



HYBRIDS, VARIETIES, AND OTHER TOPICS. 



What is apparently a case of hybridization resembling that of 

 Basilarchia arthemis and B. astyanax among butterflies occurs in 

 Virginia between two species of Trimerotropis . T. citrina has been 

 already referred to as being widely distributed in the Southeastern 

 States, frequenting sandy areas. At Cape Henry and Virginia Beach 

 it meets T. maritima, a more northern species whose range extends 

 to North Carolina at least. Where the ranges of the two overlap, 

 typical forms of both species are found, and intergrades of all 

 degrees of resemblance to either occur in numbers. Were not the 

 typical forms present it would appear to be simply intergradation, 

 as appears to be the case in the related genus Scirtetica. In the 

 latter genus 6*. marmorata, found in Massachusetts and Connecticut, 

 differs markedly in degree of pigmentation of the wings and slightly 

 in structure from 6*. picta of Florida ; but North Carolina specimens 



