THE SHIELD-BACKED BUGS. 37 



h. Second and third joints of beak subequal in length, the fourth 

 shorter; tube of osteole distinctly shorter than the canal, the 

 latter almost flat, the peritreme or supporting plate shining, 

 shallowly and sparsely punctate; length, 9 — 11 mm. 



V. Symphylus, p. 43. 



/;/;. Second joint of beak as long as third and fourth united, the 



third and fourth subequal; tube of osteole as long as canal, 



the latter distinctly grooved, the peritreme opaque, deeply 



and closely punctate; length 6 — 7 mm. VI. Stethaulax, p. 44. 



cc. Second joint of antennae distinctly shorter than third; osteolar 



canal long, slender and curved forward; length less than 9 mm. 



VII. Hom^mus, p. 46. 



bb. Pronotum with a distinct transverse submedian groove; head 



deflexed or bent downward. 



i. Groove of pronotum narrow, sharply delimited; front of head 



angulate or obtusely rounded ; fourth and fifth ventrals with a 



very finely striated stridulatory area; length, less than 6 mm. 



;'. Side margins of head and pronotum entire. VIII. Camirus, p. 49. 



jj. Side margins of head and pronotum finely and irregularly 



toothed. IX. Acantholoma, p. 50. 



ii. Groove of pronotum wide, not sharply limited ; front of head broad 



and subtruncate; ventrals without a stridulatory area; length 



6 — 7 mm. X. Phimodera, 17 p. 51. 



aa. Scutellum narrow, oblong, not covering any portion of the costal 



border of elytra; ventrals without a stridulatory area; second 



joint of antennae slightly curved; length, 7 or more mm. 



XI. EURYGASTER, 17 p. 52. 



I. Tetyra Fabricius, 1803, 128. 



Species of large size, having the head nearly as broad in 

 front as behind, tylus convex, slightly surpassing the cheeks ; 

 second and third joints of antennae (in our species) subequal, 

 fourth nearly one-third longer, fifth equal to or slightly longer 

 than fourth ; beak reaching second ventral segment or beyond, 

 its second joint as long as third and fourth united ; scutellum 

 very broad, covering the apical third or more of costal border 

 of elytra ; connexivum exposed beyond the middle ; osteolar 

 tube reaching middle of its supporting plate, its opening very 

 small, the tube not continued as a definite canal, but as a broad 

 expansion with apical margins elevated. Two of the three 

 known North American species occur in our territory. 



KEY TO EASTERN SPECIES OF TETYRA. 



a. Antennae black annulated with white near the tip and base of each 



1T These two genera are, by Stal (1872), and most subsequent authors, placed in 

 the subfamily Odontotarsina? which is separated from the Tetyrina? only by the 

 absence of the so-called stridulatory area on the fourth and fifth ventrals. In old or 

 dirty specimens this character is often very difficult to ascertain, and I doubt very 

 much its being one worthy of subfamily division. 



