456 PROCEEDINGS OF THE NATIONAL MUSEUM vol. ni 



Pangaeus) or limited (figs. 102, 104) laterally and posteriorly and not 

 reaching into posterolateral angle (subgenus Homaloporus). 



Metapleuron (figs. 103, 104): Flattened; osteole opening posteriorly 

 on peritreme; latter not surpassing middle of segment, apex not 

 difi'erentiated; evaporatorium occupying mcsal two-thirds of segment, 

 outer margin variously concave; polished lateral space impunctate. 



Legs: Moderately long; anterior tibia (fig. 127) compressed, with 

 nine to ten stout spines dorsally, not or only slightly siu-passing tarsal 

 insertion; middle and posterior tibiae usually slender, latter modified 

 in shape and spine arrangement in males of several species (figs. 

 152-159). 



Sternites: Alutaceous to polished; with one or two lateral submar- 

 ginal setigerous tubercles; sutures entire or finely denticulate. 



Type of genus. — Aethus margo Dallas (1851), subsequently desig- 

 nated by Van Duzee (1914, p. 378). The name margo as well as 

 several others have been found to be synonjTiis of Cimex aethiops 

 Fabricius. Further data on tliis synonymy can be found in the dis- 

 cussion of Pangaeus aethiops. The type of subgenus Homaloporus is 

 congruus Uhlcr by nature of Uhlcr's monobasic proposal for his 

 generic name. 



Distribution. — A New World genus, Pangaeus ranges throughout 

 North America from southern Canada (Provancher, 1886) south 

 through Central America and the West Indies into South America as 

 far south as Argentina and Uruguay. The two "species," douglasi 

 and scotti, that Signoret (1882) described from Australia and New 

 Zealand respectively may or may not have been correctly labeled. 

 Study of the types of both of these species shows that they were based 

 on undoubted specimens of the common North American species 

 bilineatus (Say). For further information on this see the remarks 

 under Pangaeus bilineatus. 



Discussion. — The nume^' Homaloporus" has long been maintained 

 in full generic status for one North American and one South American 

 species which resembled members of the genus Pangaeus in having an 

 impressed, subapical line on the pronotum, but differing in possessing 

 a submarginal row of pegs on the head. As the present study progres- 

 sed and the value of the head vestiture for generic separation lessened, 

 a reevaluation of the relationships of these two "genera" became 

 necessary. 



The presence of an undifferentiated apex of the peritreme coupled 

 with the impressed subapical line on the pronotum definitely allied 

 these two taxa and separated them from all other Cydnidae. Experi- 

 mental joining of the two revealed such a starthng similarity of 

 development between the northern members of each and between the 

 southern members of each that one could not believe this to be a case 



