162 FAMILY V. TETRIGID.E. THE GROUSE LOCUSTS. 



Hancock (1906) lists 49 nominal known species, 17 of them 

 from North America, but a number of these are now known to be 

 only long- or short-winged forms or geographic races of the same 

 species, only five valid species and three races or varieties being 

 recognized from our territory. 



KEY TO EASTERN SPECIES OF ACRYDIUM. 34 



a. Median carina of pronotum more or less distinctly elevated along its 

 entire length; dorsal surface of prouotum higher in the middle, 

 sloping on the sides, more or less rugose or wrinkled as well as 

 granulated; sides of vertex sinuate, its disc therefore feebly nar- 

 rowed opposite the middle of eyes. 

 b. Front of vertex, viewed from above, obtusely angulate, its median 



carina not projecting beyond the sides (Fig. 3.) 

 c. Body very slender, the pronotum relatively narrow between 

 the shoulders and posteriorly attenuate; frontal costa, viewed 

 from the side, very slightly sinuate between the eyes; upper 

 or tegminal sinus of lateral lobes nearly as deep as the lower 

 one. 65. GRANULATUM. 



cc. Body stouter, the pronotum much broader between the should- 

 ers, much less attenuate but acute posteriorly; frontal costa 

 viewed in profile distinctly sinuate between the eyes; teg- 

 minal sinus obviously more shallow than the lower one. 



66,. BRTJNNERI. 



bb. Front of vertex, viewed from above, convex or rounded, its me- 

 dian carina distinctly projecting as a small tooth beyond the 

 sides (Fig. 2b.) 



d. Median carina of pronotum not elevated or compressed and 

 curved between and before the shoulders; frontal costa but 

 slightly sinuate between the eyes; form more slender. 



67. ORNATUM. 



dd. Median carina of pronotum between and before the shoulders 

 obviously more elevated, compressed and more or less curved; 

 frontal costa distinctly concave or sinuate between the eyes; 

 form more robust. 



e. Tegminal sinus almost as deep as the inferior one; middle fe- 

 mora enlarged, in male nearly one-half as wide as long; pro- 

 notum more slender, in short form distinctly surpassing the 

 tips of hind femora. 67a. HANCOCKI. 



ee. Tegminal sinus much more shallow than the inferior one; mid- 

 dle femora three times or more as long as wide; pronotum 

 broader and shorter, in the short form scarcely reaching the 

 tips of hind femora. 68. ACADICUM. 



OCT. Median carina of pronotum indistinct, not at all or very little ele- 

 vated; dorsal surface of pronotum flat or nearly so, the surface 



3 'Hancock (1909, 414) described Tctti.r (Acrydiinn) ainc>'icaiia and its short form di- 

 morplia from specimens in the Oxford (England) University Museum. Since their or- 

 iginal locality is in doubt, being designated only as "Amer. b.," they are not consid- 

 ered in this work. 



