THE CANADIAN ENTOMOLOGIST 167 



than to add to the subdivisions of Pyrgus still another. Should transition 

 forms exist, Sceloihrix must certainly be absorbed, but no such forms are 

 known to me : — the tibial tuft and the appendages are either completely 

 developed, or entirely absent. 



Maculata is characterized by very acute fore-wings, by the particular 

 color and marking of their undersides, and above all by the white fringe 

 being marked with black only on the upper side, and not both above and 

 below as in the other species. Appendages of the pectus and tuft of the 

 tibiae in the male well developed, the latter extending to the end of the 

 first tarsal joint. The other species stand very close together, and it hap- 

 pens here again, as in other very natural groups, that the genera which are 

 easiest to define, are those in which the species are the most difficult — 

 declaring distinctly that if the genus should be easy to define, the parts of 

 which it consists must be very homogeneous. Here are chiefly those 

 species or varieties nearest to alveiis : fritiUum, serratulcs, cacalice, anrfro- 

 //icdcB (and quite independent of the Ramburian cersii, carlince and o/iopordi, 

 concerning which nobody has accurate knowledge), which difficult in 

 themselves to separate by fixed characters, become in the mass still more 

 difficult to separate from their originals, the more that the number of speci- 

 mens compared increases, and their localities widen. The reason for this 

 may be that these forms have not begun until recent times (geologically 

 speaking) to separate themselves from their common originals ; and as 

 species (in a systematic sense), have not yet become perfect, the inter- 

 mediate forms still existing as such in many localities, while in others they 

 have disappeared. The evidence for this last position appears to me to 

 be given in the following observation. The two forms of the alrcus-groxnp, 

 which occur here in Rhoden, are fritiUum (H. 464-5, HS.) and scrratn/ce 

 (HS. fig. 18-20) ; the supposed stem-species, alvcus (H. 461-3) is entirely 

 absent. The first two fly in the same locality (upon the Muschelkalk 

 formation), which I visit diligently every year, and where I find my 

 richest source for Uiurnals and many other Lepidoptera. FritiUum, and 

 also serratuhe, appear here in quite typical form, and 1 have not yet met 

 with an example which has raised a doubt as to which of the two forms it 

 should be referred, nor which had assumed the characteristics of alvcus. 



I found fritillum on this spot during the whole of June, and again at 

 the end of August, and in September ; also, during several years, singly, 

 in the last half of July. In former years this butterfly appeared some- 

 times in large numbers, but recently it has become much more scarce. 



