2 NORTH AMERICAN BLATTIDAE 



Other considerable collections of Blattidae, particularly those from 

 Africa, has aided, but mainly in affording negative evidence of 

 close affinity, the species examined representing, in the great ma- 

 jority of cases, groups and genera having but little bearing on those 

 at present under consideration.^ 



Generic association of the species was at once found to be a 

 serious problem, the difficulties in the present work being particu- 

 larly complex in the Pseudomopinae, where two genera, Blattella 

 and Ischnoptera, were found to include each a large number of 

 valid generic units, while Kakerlac, Ceratinoptera and Temnop- 

 teryx have been used as a veritable dumping ground for a varied 

 assortment of perplexing forms, many agreeing only to some ex- 

 tent in the degree of reduction of the tegmina and wings. 



Treatment 



Detailed descriptions of each genus and species in the present 

 paper were deemed inadvisable, but careful analyses of the features 

 of real differential value are given as well as full descriptions of 

 coloration. Particular attention is also given to the range of vari- 

 ation in each species, as confusion in subsequent work is much the 

 more likely to occur upon encountering features representing mere 

 individual, though striking, variations. 



The treatment of certain groups is more detailed than that of 

 the majority. Thus, the very large series of the genus Parcohlatta 

 has led us to discuss in detail the species of the group Ischnopterites 

 included in the present study. The confusion which has existed 

 in the group Blattellites has also necessitated a more elaborate 

 study of the genera and the species there considered. In the 

 Polyphaginae, series of intimate significance, from both the south- 

 western United States and Mexico, have led us to include all our 

 North American material in the present treatment, not confining 

 the study, as almost universally elsewhere, to material from north 

 of the Mexican boundary. 



3 As an examiile; the African species, which have been described as IscJinoptera, now 

 before us, are indeed members of the Group Ischnopterites, but in no case arc they re- 

 ferable to Ischnoptera s. s., or to any other of the New World related genera. 



