1910.] NATURAL SCIENCES OF PHILADELPHIA. 1 4v} 



from Live Oak, Florida, have six of their number with the pronotum 

 caudate. It is quite probable that immediate environment is the 

 governing factor in the production of the two types, and we have 

 here an interesting Held for experimental work. 



In size such variation as is found is, apparently, in the main 

 individual or environmental, while the rugosity of the dorsum of the 

 pronotum is another variable feature in all probability dependent 

 on environment. The fluctuations in the latter respect are con- 

 siderable, but in no case are they sufficient to cause confusion with 

 .V. bolti 



The variation in the form of the frontal costa is quite appreciable, 

 and of one hundred and ninety-six specimens examined for this 

 character, one hundred and fifty-six have the interantennal section 

 scutcllate or ''flask-shaped," nine show a slightly different type, 

 t \\ enty-three are more strongly divergent and three have the lateral 

 margin< of the costa regularly divergent ventrad as in the majority 

 of .V. bolteri. These three aberrant individuals are from widely 

 separated localities — Fredericksburg, Virginia; Homerville, Georgia, 

 and Live Oak, Florida — and in no other respect do they approach 

 bolteri. 



In coloration we find this species to be more uniform than most 

 of our common nearctic grouse-locusts, by far the greater portion 

 of the material being brownish, with or without triangular blackish 

 posthumeral areas. The variation consists of a more or less complete 

 "pepper and salt" effect, rarely a pale "saddle," a pale outline of 

 the median carina of the pronotum and very infrequently paired pale 

 areas on the dorsal surface of the caudal femora. In addition to 

 these rather infrequent differences, numerous specimens are strongly 

 infuscate, occasionally almost black, while quite rarely they are 

 almost uniform cinereous. The general tone is undoubtedly a 

 response to the environment, those from sandy or clayey soils, as at 

 Homerville, Live Oak, Greensboro and Fredericksburg, showing 

 the paler shades, but this is not absolute, as individuals from Jackson- 

 ville taken on bare white sandy soil are very dark. Apparently the 

 degree of moisture in the soil produces no response in color, as the 

 material from Augusta, which was taken in open, moderately dry 

 pine woods, averages darker than that from Homerville which was 

 taken on damp sandy ground. 



From the mapped distribution of this species it will be seen that 

 the northern boundary of its range is in the Upper Austral zone, 

 probably being the upper boundary of that area, southward the 



