170 REPORT UNITED STATES ENTOMOLOGICAL COMMISSION. 
A. A. Presternum unarmed. 
a. The styles of the subgenital plate of the male fixed (not movable). 
Siexroxys. Herm. 
aa. Stylos of the subgenital plate of the males articulated (movable). 
b. Median carina of the prouotum distinct throughout Decticus. Serv. 
bb. Median carina of the pronotum wanting or visible only on the posterior 
portion. 
c. Dorsum of the pronotum rugose ; elytra squamajform ; wings absent. 
Paorodonotus. Burin. 
cc. Dorsum of the pronotum smooth. 
d. Elytra short but not squamajform Platyclein. Fieb. 
dd. Elytra squamajform ; pronotum without distinct lateral carinas. 
e. Anterior tibia? with but three or four spines in front ; in one 
row Thamnotrizon. Fisch. 
ce. Anterior tibia? with six to eight spines in front ; iu two rows. 
Anabrus. Hald. 
From this table it will be seen, as stated, that A. Haldemanii Girard 
does not belong to the genus in which it was originally placed. For 
this reason we have omitted it from the present paper. 
We may note iu passing that according to the arrangement of the 
genera as here given, Thamnotrizon scabricollis Thos., which appears to 
be closely allied to this genus, and will by most unscientific observers 
be taken for A. purpurascens, must be removed to the genus Psoro- 
donotus. 
The genus Anabrus appears to be represented only in that portion of 
North America north of Mexico and west of the Mississippi. Four spe- 
cies are mentioned, A. simplex Hald., A. purpurascens Uhl., A. similis 
Scudd., and A. coloradus Thos. The third, A. similis Scudd., appears 
to be but a variety of A. purpurascens ; we therefore have but three dis- 
tinct species. 
These may be distinguished from each other by the following charac- 
ters : A. coloradus is the smallest, and has the abdomen distinctly marked 
by transverse bands. A. purpurascens, dark purplish-brown, mottled 
with yellow. A. simplex, dark shining brown. This species varies con- 
siderably in color, being found of every shade from light brownish-yel- 
low to almost entirely black ; specimens are sometimes found that are 
partly yellow and partly black or dark-purple. 
ANATOMY OF ANABRUS. 
External anatomy (Figs. 3, 4). — The following account is based on the 
external structure of Anabrus simplex. 
The head. — In these crickets, the first region of the body, or head, is 
large and rounded, the epicranium, or piece composing the bulk of the 
head, being large, while the eyes are small and situated far apart; be- 
tween them the vertex rises into a shield-shaped prominence, on each 
side of the base of which is situated a simple eye (ocellus), forming two 
pale, oval, roundish spots easily overlooked. The third ocellus is more 
