55 



often with a slightly irregular course, to the margin of the wing; in 

 the fragment there are eight such veins on one wing and six on the 

 other and more imperfect wing, in both cases about equidistant, but 

 more regular and straighter on the left than on the right wing; in 

 both, also, one of the secondary veins, and one only, arising shortly 

 before the middle of the wing, is forked ; on the left side close to its 

 origin, on the right side near the middle of its course. Both borders 

 are perfectly preserved on the right wing, showing it to be 10 mm. 

 broad; the length of the longer fragment is 20 mm., and the probable 

 length of the wing is about 35 nun. 



On Dsmoupiiism in Western A.cridians. 



The different forms had in many instances been described as dis- 

 tinct species, and, indeed, been referred to distinct genera ; the short 

 winged forms having usually been placed in Pezotettix, while the 

 long winged types had been described as Callipteni. This peculiar- 

 ity is found in ten or twelve species, mostly occurring in the Missis- 

 sippi valley ; usually there is a very decided difference in the length 

 of the wings, althouiih in the long-winged forms the tegmina seldom 

 surpass or even reach the tip of the hind femora ; and no interme- 

 diate forms occur. In one instance three varieties occur, which are 

 with little doubt to be referred to one species ; and in this case the 

 variety with the longest wings has tegmina which extend past the 

 hind femora. The dimorphic forms of any one species are found at 

 the same stations, and can not be considered racial. Similar 

 dimorphism has long been known in Orthoptera, and this should 

 doubtless serve as a sufficient reason to group together several of the 

 foi-ras of Xiphidium which had been described as distinct species, 

 and the two northern forms of Gryllotalpa, as well as some so-called 

 species of Gryllus and Nemobius. 



