290 FAMILY IX. — ARADIDjE. 



side; females with two visible genital segments, the first with 

 a lobe each side partly visible from above, the second much 

 smaller, terminal, not visible from above. 



The members of this genus are more numerous in the north- 

 ern countries of the world than are those of the Mezirinae, the 

 main distribution of the latter being in the tropics. Brachyp- 

 terous forms of a number of species are known. About 60 

 species of Aradus are known from North America, 33 species 

 and three varieties from our territory. For convenience of 

 treatment they are separated into seven groups. 



KEY TO GROUPS OP EASTERN SPECIES OF ARADUS. 



a. Beak extending back of base of head; side margins of pronotum 



more or less explanate. 



b. Median carina? of pronotum distinct, usually extending to front 



margin ; antenna? longer than head. 



c. Second antennal segment but slightly longer than third, both 



slender and cylindrical; length 8 or more mm. Group I, p. 290. 



cc. Second antennal segment generally distinctly longer than third, 



one or both often not cylindrical. 



d. Third antennal segment about one-half thicker than second, 



the latter with apical third or more pale (fig. 3c) 47 ; length, 



7.5—9 mm. Group II, p. 292. 



del. Third antennal segment slightly if at all thicker than second. 



e. Antenna? very robust, at the widest point distinctly thicker 



than front femora (figs. 6c— 16c). Group III, p. 293. 



ee. Antenna? more slender, often cylindrical, not or but slightly 



thicker than front femora (figs. 19c — 22c). 



/. Side margins of pronotum distinctly serrate, never deeply 



sinuate (figs. 26d — 36d) ; corium always strongly dilated 



at base, its sides never straight. Group IV, p. 297. 



//. Side margins of pronotum entire, evenly granulated or very 



rarely denticulate, often deeply sinuate (figs. B9d — 53rf) ; 



corium either dilated at base (the lateral margin sinuate) 



or not so dilated. Group V, p. 306. 



66. Median carina? of pronotum but slightly developed, obsolete in 



front; antenna? scarcely longer than head, very robust, the 



third segment not twice as long as first (fig. 55c) ; length, 



less than 4 mm. Group VI, p. 314. 



aa. Beak not reaching base of head; pronotum more or less distinctly 



trapezoidal, the side margins not explanate. Group VII, p. 315. 



Group i. — Aradus. 



This group comprises two of our larger eastern species hav- 

 ing the antennae slender, second and third joints cylindrical, 

 subequal in length. 



> T The figures cited in the keys and descriptions of the semis Annlns mostly refer 

 to those on Plates I. II and III. occurring on pages 289. 300. and 306. 



