THE CANADIAN ENTOMOLOGIST. 125 



the number of spurs in the same species (Acidalia rusticata), a second 

 instance of a varying species (see below Pamphila Alcides). 



Of no more value in a systematic relation are the spines (dornborsten) 

 of the tibiae, so far as-I can judge from the limited number of species 

 that I have examined. The genus Pamphila affords ample evidence of 

 this ; Pyrgus, also, attests to its truth, for its only spined species, crib- 

 rellum, no one would ever think of separating, because of this peculiarity, 

 from tesse/tum, etc. 



The spines the most generally occur on the middle tibiae, where they 

 are always the most strongly developed ; occasionally they are only present 

 here. Then follow, both in frequency of occurrence and in their develop- 

 ment, the posterior tibiae ; and lastly the anterior tibiae. Often the 

 spines of both these legs are so slight, or so covered up by hair and 

 scales, that one has great difficulty in recognizing them, and their actual 

 presence seems a matter of doubt. The manifold differences which are 

 presented in the form of the club of the antennae are of value for sys- 

 tematic purposes ; but, unfortunately, these differences are not often 

 sharply defined and are difficult to express clearly in words. And there 

 are not wanting species deviating from their generic association only in 

 these points, that is to say, aberrent forms (such as Pyrgus Poggei), which 

 could not be separated without an unnatural disruption of genera. 



The palpi, particularly in the form and direction of their apical joint, 

 afford some useful generic characters, while they offer, also, negative 

 indications similar to those taken from the form of the knob of the 

 antennae. Some other valuable systematic peculiarities are developed 

 only in the male sex, while the female has in general remained a step 

 behind. Their use as generic characters, therefore, cannot be recom- 

 mended in this, as in other difficult groups, nor can they be wholly dis- 

 pensed with. To these belong the costal fold and the discoidal stigma 

 of the fore wings, the hair-pencil of tire hind tibiae, the appendages of the 

 hind breast,* and the abdominal fossa (bauchgrube). 



The costal fold affords in the European species, in which it is present, 

 only unimportant differences. It begins near the base of the anterior 

 margin and terminates on or near its middle. The portion of the anterior 

 margin, which it here covers, is not clothed with scales, but with a peculiar 



[Hiitterfireast ; Metasturnum (Burmeister), post pectus (Kirby).- L.1 



