46 STUDIES IN AMERICAN TETTIGONIIDAE (oRTHOPTERA) 



Atlanticus glaber Rehn and Hebard 



Atlanticiis calcaratus new species 



In addition, Mr, Caudell has kindly furnished us with infor- 

 mation on the type of Walker's Decticus derogatus ( = americanus), 

 which is in the British Museum. 



Key to Species 



This key is admittedly artificial in a number of features, as it 

 has been found almost impossible to construct a key to the forms 

 along natural or presumably phylogenetic lines. The use of the 

 plate figures in connection with the key is strongly recommended. 



A. Medio-internal spur of caudal tibiae more than twice as long as the ven- 

 tro-internal spui". (Disk of pronotum narrow, subequal in width. Proster- 

 num unspined.) cjflcaratus new species 



AA. Medio-internal spur of caudal tibiae distinctly less than twice or not 

 more than twice as long as the ventro-internal spur. 



B. Pronotal disk in both sexes very narrow, subequal, the greatest width 



contained nearly or quite two and one-half times in the greatest length 



of the disk, with lateral angles subparallel. glaber Rehn and Hebard 



BB. Pronotal disk in both sexes more or less distinctly expanding caudad, 



the greatest (caudal) width ahnost never contained twice in the greatest 



length of the disk, the lateral angles more or less distinctly diverging caudad. 



C. Lateral angles of pronotal disk distinct but rounded in section and 



never sharp and carinate. Tegmina of male almost or quite completely 



covered by the pronotum. 



D. Size medium. Pronotum with the width of the disk at cephahc 

 fourth not less than that at cephahc margin; caudal margin of disk 

 arcuato-truncate. Caudal femora not greatly inflated proximad. 

 Cercus of male short, robust, with short tooth. dorsalis (Biu-meister) 

 DD. Size very large (largest in the genus). Pronotum with the width 

 of the disk at cephalic fourth appreciably less than that at cephalic 

 margin; caudal margin of disk strongly arcuate. Caudal femora 

 greatly inflated proximad. Cercus of male elongate, corniform, with 

 elongate equally corniform tooth. gibbosus Scudder 



CC. Lateral angles of pronotal disk very distinct, strongly angulate in 

 section, sharp and frequently carinate. Tegmina of male never com- 

 pletely covered by the pronotum. 



D. Cercus of male relatively elongate. Subgenital plate of male 

 narrowly and deeply fissate. Subgenital plate of female deeply divided 

 and lateral portions of same sublanceolate. (Ovipositor straight or 

 faintly decurved, apex ventral.) americanus (Saussure) 



DD. Cercus of male relatively short, robust. Subgenital plate of 

 male angularly emarginate to various degrees, never fissate. Subgenital 

 plate of female V- or U-emarginate, lateral portions of same never sub- 

 lanceolate. 



