366 BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



Sun.mary of the CydnidcB of N'orth America. 



Fam. CYDNID^. 

 Form geuerally oval, suborbicular, or quadrangularly elliptical ; head 

 clypeate, semicircular; antennss of five joints (exceptionally of four), 

 which are loosely united by slender threads between the second and 

 third, third and fourth, and fourth and fifth joints, inserted under the 

 flat margin of the sides of the head; rostrum of four joints, the second 

 of which is usually compressed ; scutellum either broad and bluntly 

 rounded or triangular, with the apex pressed down ; tibise beset with 

 stout spines, generally fossorial ; the first ventral segment very narrow, 

 generally occult. Color generally black, or piceous. 



I. Tribe CYDNINL 



Femora compressed ; tibise closely armed with stout spines, the ante- 

 rior pair more or less compressed ; the tarsi slender, filiform. 



Scheme of genera. 



I. Scutellum triangular, convex: 



Head with erect, submarginal bristles, or teeth : 

 Body very deep and convex : 



Ostiolar canal fusiform Gyrtomenus. 



Ostiolar canal a long gutter Amnestus. 



II. Scutellum broadly rounded : 



Head with comb-teeth: 



Body deep and convex : 



Ostiolar canal obsolete, sulcate, with raised margins ; sur- 

 face closely hairy Trichocoris. 



Ostiolar canal short, at tip enlarged into a circular auricle ; 

 surface hairy exteriorly Microporus. 



III. Scutellum triangular, narrow at tip : 

 A. Head with submarginal comb- teeth : 



a. Pronotum, collum with an impressed, submarginal, deeply 



arcuated line : 

 Ostiolar canal reaching almost to the outer end of the 



episternum, flat, clavately rounded at tip.. Macroporus. 

 Ostiolar canal short, ligulate, obliquely indented next the 



tip o Somaloporus. 



Ostiolar canal half the length of episternum, flat, fusiform, 



scale-like behind, oblique at tip ; pronotal submarginal 



line obsolete - ^thus. 



h. Pronotum without the arcuated line : 



Ostiolar canal short, narrow, subfusiform, with the ostiole 



at tip ^. Ehytidoporus. 



Ostiolar canal obsolete, shorter than the coxa, narrow-lig- 



ulate Cryptoporus. 



