398 PROCEEDINGS OF THE NATIONAL MUSEUM vol. m 



suture straight or bisinuate; membrane about two-fifths of hemelytral 

 length, yellow or milky hyaline. 



Propleuron: Polished, impunctate; prosternal carinae low; anterior 

 margin broadly and weakly lobed on either side of middle. 



Mesopleuron (fig. 90): Slightly concave, shining, evaporatorium 

 very lunited or absent and replaced by rough, close, oblique rugae 

 on inner basal half; posterior margin entire; mesosternum carinate 

 medially, with numerous long hairs. 



Metapleuron (fig. 90, a-d) : Rather convex, shining, evaporatorium 

 restricted to simple outline of peritreme and may become evanescent 

 apically, remainder of surface shining, weakly rugose or with few 

 punctures; peritreme reachmg almost to or slightly past middle of 

 segment; terminal modification strongly to weakly auriculate (figs. 

 90,a-(/j always with anterior part extended posteriorly around 

 osteolar opening which is visible ventrally. 



Legs: Short; anterior tibia (fig. 118) moderately dilated, with seven 

 or eight stout, blunt spines on dorsal margin, not prolonged beyond 

 tarsal msertion; tarsal II shortest; middle and posterior tibiae sub- 

 terete, latter (fig. 151) straight, dorsal and ventral spines equal in size. 



Sternites: Convex, polished, wrinkled and more or less punctured, 

 each segment with transverse row of setigerous punctures approaching 

 posterior margin toward middle; each segment laterally with sub- 

 marginal elevated band which gives rise to two or more than twelve 

 long hairs per segment. 



Type of genus.— Mzcro^orits obliquus Uhler (1872, p. 394), mono- 



typy. 



Distribution.- — Two species of this genus are known to occur 

 throughout the enth-e United States (but only from scattered local- 

 ities in the eastern half) and south to central Mexico; the third only 

 from Argentina in South America. 



Discussion. — The division of the genera of the Cydninae into two 

 groups based upon the absence or presence of a differentiated terminal 

 part of the peritreme has proved to be very workable in nearly all 

 cases. The "exception" proves to be in the present genus — Micro- 

 porus. In the original description of the Microporus, Uhler (loc. cit.) 

 said, "Osteolar canal short, at tip enlarged into a circular auricle." 

 He described two species in this genus, obliquus, the genotype, and 

 testudinatus. Several years later, Distant (1880, p. 8), after quoting 

 Uhler's statement concerning the "circular auricle," described a third 

 species, mexicanus. From all this one would assume that the circular 

 auricle was a characteristic of all three forms. The first clue that 

 such was not always the case appeared in Signoret's (1881b) intro- 

 ductory remarks concerning Uhler's genera. At that time Signoret 

 (1881b) transferred testudinatus to Aethus (defined on p. 423 as having 



