CYDNIDAE OF THE WESTERN HEMISPHERE FROESCHNER 347 



somewhat nodular prominence, or umbone, near each lateral margin 

 and a differing sm-face sculpture. Anteriorly, on either side of the 

 midline of the prosternum, there may be present a longitudinal 

 ridge — the prosternal carinae. 



The dorsal surfaces of the mesothorax and metathorax, except for 

 the scutellum of the latter, are usually hidden from view and so have 

 been little used for taxonomic characters. In all species except 

 those of Amnestus the scutellum is typically pentatomoid in that it 

 is very large and surpasses the apices of the clavi, preventing the 

 latter from coming together to form a claval commissure. Therefore, 

 it is quite surprising to find that in Amnestus the scutellum is very 

 short, permitting the clavi to reach beyond its apex and form a claval 

 commissure. The scutellum itself varies in ratio of length to basal 

 width and in having the apex narrowed (fig. 79) or not (fig. 80). 

 The subapical width of the scutellum at the level of the claval apices 

 is often a useful measurement when compared with the width of the 

 membranal suture, the line of union between the apex of the corium, 

 and the base of the membrane. The ventral aspects of the mesothorax 

 and metathorax furnish a number of characters of generic, subgeneric, 

 and specific importance. In the present paper the area laterad 

 of the coxal insertions is referred to as the pleuron, that between 

 the coxal insertions as the sternum. A dull, finely roughened evap- 

 oratorium may be present or absent on the pleurae of one or both 

 segments; its occurrence plus its extent may be of varying value 

 depending on the species under consideration. The punctation in 

 the polished area laterad of the evaporatorium, referred to as "lateral 

 area," may be of specific value. The metapleuron bears the external 

 opening of the scent gland, usually referred to as the osteole. The 

 osteole occurs in a cuticular modification referred to here as the peri- 

 treme. The peritreme consists of a pah- of close-set transverse ridges 

 which may or may not be in contact along their summits; the anterior 

 ridge is usually more strongly developed and frequently modified 

 beyond the osteolar opening. When present, this apical modification 

 furnishes good characters for definition of genera. The osteolar 

 opening may be situated ventrally on the peritreme, or posteriorly 

 where it is concealed by a projecting ledge. In Amnestus the middle 

 carina of the mesosternum and metasternum is strongly elevated, 

 separating the coxal cavities. 



The basal thickened part of the anterior wing is divided into three 

 main areas — the clavus next to the scutellum, the triangular discal 

 area or mesocorium between the clavus and the radial vein, and the 

 narrow exocorium between the radial vein and the costa. The dis- 

 tinctness, relative sizes, and punctation of these areas plus the pres- 

 ence or absence of a variable number of setigerous punctures on the 



