198 PROCEEDINGS OF THE ACADEMY OF [April, 



yellow line narrows and finally dies out, the fastigium broadens out 

 and the pronotum and head become more robust toward the "rubi- 

 ginosa" type in the intermediates in certain extensive series. We 

 have such series of alutacea from a number of localities in New 

 Jersey, South Carolina and Georgia. The proportionate depth of 

 the caudal femora in general is greater in the rubiginosa type, but 

 this is by no means an absolute rule, as some series of that phase 

 show all sorts of variation in this respect. The "alutacea" phase, 

 however, is more uniform in having the femora more slender. The 

 number of scutes in the paginal pattern on the caudal femora also 

 varies greatly and without phase correlation. 



We have examined a number of New England specimens of 

 "alutacea" and " rubiginosa " determined by Morse, and the remarks 

 he has made about their differences hold true, but when material 

 from New Jersey southward is considered the inter-relation of the 

 two forms becomes so complicated that they cannot be separated 

 when large series are considered. 



Taking up the question from the standpoint of habitat, it is true 

 that as a rule the striped types prefer moist areas with bracken, etc., 

 while the brown forms are more at home in dry woods and brush, 

 old fields and among dune thickets, although numerous specimens 

 of each phase have been taken in the habitat preferred by the other. 

 It is highly probable that the near future will show similar environ- 

 mental preferences by other forms of this genus now considered of 

 specific rank, but doubtless of no more standing relatively than the 

 phases of obscura and alutacea. Sufficient field observations have 

 been made, outside of those in the eastern United States, to convince 

 us that in the genus Schistocerca color per se is, as a rule, a poor 

 specific criterion, while sufficient laboratory experience has been 

 had to convince us equally well that, in this genus, certain structural 

 features are quite plastic, and in consequence to be used with caution 

 and discrimination in diagnostic work. 



The principle of dimorphism, which plays such an important part 

 in the Orthoptera, satisfactorily explains to us the problem here 

 considered. In the present cases the color differences are quite 

 decided, with a fair number of non-typical specimens nearer one 

 type than the other and a relatively smaller number really interme- 

 diate. The structural differences, generally correlated with the 

 color differences, are typically quite appreciable, but their constancy 

 fluctuates in different localities. Color dimorphism is known to 

 exist in certain genera not distantly related to Schistocerca and 



