14 STUDIES IN AMERICAN TETTIGONIIDAE (oRTHOPTERA) 



from the Great Basin region, no specimens having been examined 

 from southern Cahfornia, Nevada, Utah, southern Idaho, western 

 Wyoming and Colorado, or Arizona and New Mexico west of the 

 Rio Grande. 



The center of distribution of the genus is in the Middle Atlantic 

 states, the greatest percentage of the forms occurring in the 

 region comprising the states of Pennsylvania, New Jersey, Dela- 

 ware, Maryland and Virginia, where in the northern end of the 

 Coastal Plain no less than ten of the species of the genus occur. 

 To the southward the number of forms decreases slightly and in 

 the Mississippi Valley region there is a still further diminution, 

 until but three forms are known to reach the region of the Rocky 

 Mountains and of these but one is known to occur west of that 

 uplift. In coastal and southern Texas the number of species is 

 lower than in the Middle West and from the whole of Mexico we 

 at present know of but two forms. 



Variation. — An examination of certain characters which have 

 been used by previous authors for differentiating the species of 

 this genus shows that they are either entirely unreliable or only 

 of occasional application. The first and most important of 

 these is the number of spines on the ventro-external margins of 

 the caudal femora. This character has been given a position of 

 prime importance; as a matter of fact, as in Conocephalus {Xiphid- 

 ium of authors), quite a few species show considerable individual 

 variation in the presence or absence of these spines, while prac- 

 tically all the forms show great individual variation in the number 

 of the same when they are present. In consequence we have 

 not utilized the spination of the limbs as a major character in 

 making our key, but under each species will be found a sum- 

 mary of the amount of variation in this feature. 



The proportionate length of the tegmina and wings is another 

 feature which is, in the majority of cases, of no diagnostic value. 

 This genus, with many other Orthopterous genera, exhibits con- 

 siderable individual variation in the length of these appendages, 

 individuals taken at the same place and at the same time showing 

 marked diversity in this respect. In over half the species of the 

 genus we find a mesopterous type {i. e. with tegmina and wings 

 little or not at all surpassing the apices of the caudal femora) and 

 a macropterous type (with same very considerably surpassing 

 the femoral apices). The extremes of these conditions often 



