156 STUDIES IN AMERICAN TETTIGONIIDAE (oRTHOPTERA) 



Differential Generic Characters. — The genus Conocephalus is 

 separated with great difficulty from the genus OrcheUmum. The 

 present genus includes diminutive forms; but the smallest indi- 

 viduals of several species of OrcheUmum, the majority of these 

 found onlj^ in the extreme northern part of the range of the re- 

 spective species, are not as large as the largest specimens of Con- 

 ocephalus before us. In the present genus the stridulating field of 

 the male tegmen is normally smaller, narrower and less extensive 

 than in OrcheUmum, the vicinity of the arcuate vein not strongly 

 produced or overhanging ^ and, when looking from the dorsum, 

 the humeral trunk is never hidden.^ The male cerci, though 

 showing many different types, do not in any of the North 

 American species exhibit the type found in the majority of the 

 species of OrcheUmwn, in which the tooth is placed in a more or 

 less decided socket-like depression; all of the American species 

 of the genus have the cerci unispinose. Further usual differen- 

 ces are found in the male subgenital plate which is truncate 

 distad in the great majority of American species. ■* The females of 

 all the North American species do not have the ovipositor de- 

 cidedly arcuate, though distinctly arcuate in C. nemoraUs, 

 occasionally of this type in C. nigropleur aides, and such a 

 condition even more weakly indicated in other species.^ Mate- 

 rial of the two genera is easily separated by a decidedly 

 different general appearance, but when the characters of the 

 two are compared, the variation in each of the genera leaves us 

 unable to state a single absolute difference. 



History. — In 1815, Thunberg erected the genus Conocephalus, 

 including in it twenty-four species; under one of these, C. hemip- 

 terus (p. 272), he placed as a synonym Locusfa conocephalus of 

 Fabricius, which citation forms, under the International Nomen- 

 clature rules, t^q^e designation by tautonjany, and in consequence 



2 The opposite of this is true for the majority of, but not all, the species of 

 OrcheUmum. 



^ This is the normal condition in the species of OrcheUmum, excepting in 

 0. volanlum and 0. hradleiji, and to a less degree in 0. gladiator. 



''This is not true of C. allardi, which has a distinctive and remarkal)le male 

 subgenital plate. 



'' In Orchelimuhi, mililare is the only species having a straight ovipositor; 

 several other species have the ovipositor with dorsal margin straight but with 

 ventral margin curved. 



