CYDNIDAE OF THE WESTERN HEMISPHERE — FROESCHNER 399 



"le canal ostiolaire terinine par un lobe de formes diverses, libre a 

 I'extremite ou plus ou moins confondu avec la suture mesosternale") 

 and in 1882 he transferred ohliqims to Cydnus (defined on p. 145 as 

 having "a I'extremite du canal ostiolaire un lobe Kbre, plus ou moins 

 sureleve, en forme de cornet et plus ou moins aplati sur les cotes"). 

 From specunens which Uhler apparently furnished him, Signoret 

 iUustrated the greatly reduced terminal modification of the osteolar 

 pattern in testudinatus and the auricular development of the same 

 structure in obliquus. Since that time, authors have treated these 

 species as members of the genus Aethus or Cydnus depending on how 

 the latter taxon was defined. 



With the intense examinations of the present study the specimens 

 assigned here appeared to stand apart from all others in the Western 

 Hemisphere. And again they appeared to be best defined as Uhler 

 had done, but with a limiting statement concerning the shape of the 

 terminal process of the peritreme. In the more than 200 specimens 

 examined, the shape of the terminal process of the peritreme proved 

 to be somewhat variable but exhibited two general types. The first 

 type was large and loop-shaped with the osteole opening ventrally 

 at its base (fig. 90, a). The second type showed more variability but 

 was essentially the loop-shape greatly reduced and somewhat com- 

 pressed, but still with the osteole opening ventrally at its base (figs. 

 90,b-d). The latter, or reduced t^^pe, was found almost exclusively 

 on a series of specimens from the coastal regions of central California 

 (see distribution notes under testudinatus); while the loop-shaped 

 type was found on specimens from all parts of the range of the genus, 

 even in the central coastal area of California. 



Additional support for keeping Microporus as a distinct genus is 

 offered by features other than the peritreme. The very limited 

 metapleural evaporatorium appears unique and by itself could be 

 relied upon to separate this genus from all other Cydninae in the 

 Western Hemisphere. The combination of a complete, submarginal 

 row of pegs on the juga and the unnarrowed apex of the scutellum, 

 which is broader than half the length of the membranal suture, appears 

 in no other species of the New World except in the brems section of 

 the genus Tominotus. 



With the genus thus tentatively established, attention must be 

 dh-ected to the three nominal species described within Microporus. 

 At the specific level the student of this group is again beset by the 

 same problem — exceeding variability of characters, even those that 

 might be considered critical for separating species. Considering 

 first Uhler's two species, obliquus and testudinatus, one gathers from 

 the literature that both an eastern and a western species, respectively, 

 are represented. Attempts to separate the two on the basis of 



