74 



THOMAS SAY FOUNDATION 



posed by Klapalek, but they 

 have not been well defined. 

 In so far as recognizable, our 

 species will be found grouped 

 under them in the systematic 

 list at the end of the volume. 

 Genotype, Perl a maxima 

 Scopoli (European). 



Key to the Species. 



1. Cubito-anal crossvein 

 of forewing (except 

 in P. phalerata) situ- 

 ated more than its 

 own length beyond 

 the apex of the anal 

 cell ; first fork of 

 vein Rs far out be- 

 yond the cord ; male 

 with segment 10 

 cleft dorsally and a 

 retractile U-shaped 

 supra-anal process 

 occupying the cleft 2 

 Cubito-anal crossvein 

 of fore wing situ- 

 ated at the front of 

 than its own length 

 beyond the apex of that cell ; basal fork of vein 

 Rs involved in the cord or not remote there- 

 from ; male with no supra-anal process occupy- 

 ing the dorsal cleft of the 10th segment but 

 with the edges of this cleft elevated into geni- 

 tal hooks 20 



Male with no conspicuous lobes beneath abdom- 

 inal segments 7 and 8 (occasionally a small lobe 



on 7) : larger species 3 



Male with conspicuous lobes beneath both the 7th 

 and the 8th segments, larger on 7: small east- 

 ern species 19 



Cubito-anal crossvein well out beyond the anal 



cell 4 



Cubito-anal crossvein close to (somewhat less 

 than its own length beyond) the anal cell ; larg- 

 er, western species with copious venation 17 



Fig. 14. Perla immarginata Say. 



the anal cell or less 



