12 IOWA STUDIES IN NATURAL HISTORY 



is never sharply recurved. The hind tibiae of the males are 

 provided with a tuft attached at the proximal end and lying 

 along the upper edge of the joint in a groove formed of strong 

 scales. Vein five of the primaries is intermediate between veins 

 four and six. From these structures we may assume that the 

 immediate ancestors of the skippers had antennae enlarged at 

 some distance proximad of the distal end, leaving the terminal 

 portion slender, and that vein five of the primaries in these 

 insects had not yet formed a definite connection with either of 

 the adjacent veins. From such forms evolution has proceeded 

 with the permanent reflection of the apiculus by either a curve 

 or a sharp bend. (I can construe the reflexed club of the Pyr- 

 rhopyginae only as a further development of the Hesperiid an- 

 tenna, though this does not seem a satisfactory explanation), 

 [n addition the apiculus has been reduced as already mentioned 

 and various slight specializations have taken place. The wings 

 of the Hesperiinae have changed only in the variably complete 

 loss of vein five of the secondaries and the lengthening of the 

 cell in group A, while in the Pamphilinae vein five" of the pri- 

 maries, has formed a definite connection with the median stem 

 (English system; cubitus of Comstock and Needham), as also is 

 the case with the Megathymidae. Following these lines I have 

 drawn up the following diagram which I believe will indicate 

 better than a written discussion the relations and phylogeny of 

 the genera used in this work. The arrangement undoubtedly 

 has its faults, but I believe that it corrects a number of features 

 of former arrangements which were more or less unnatural. In 

 the main it adheres to the order of genera, which has been in 

 common use. 



Superfamily HESPERIOIDEA 

 Antennae clavate, in a few genera with the club very slender. 

 Club usually with a slender tip called the apiculus. Palpi 

 variable, usually relatively large and thick, upturned to porrect. 

 Head wide, eyes large and far apart, lashed. Insertion of an- 

 tennae near eyes. Body stout, slender in a few genera. Wings 

 relatively smaller than in the Papilionoidea and with very strong 

 venation in most genera, Primaries with twelve veins, all free; 

 cell open or weakly closed. One anal. Secondaries with eight 



