THE CANADIAN ENTOMOLOGIST. 91 



A REVIEW OF OUR GEOMETRID CLASSIFICATION.— No. 3. 



RICHARD F. FK.ARSALL, BROOKLYN, N. Y. 



The endeavour to place our species under genera based upon structural 

 characters, easily observed, yet possessing stability, has resolved itself 

 into an extensive study and rearrangement of the species themselves, 

 especially ot" the type forms, which in a number of cases are found to 

 differ from the generic requirements. I need not rehearse here the 

 opinions set forth by Mr. Meyrick, Dr. Halst and others as to the pro- 

 priety of using certain characters, whether sexual or not, in defining 

 genera. I have simply, throuiih my own investigations, sought to deter- 

 mine upon the value of those which in our fauna I have tested and found 

 to be reliable, and these I intend to use in future descriptive work, 

 dividing them into basic and auxiliary groups. 



Basic Group. 

 In this grouj) the cliaraclers do not vary as between individuals, 

 excei)t in rarely aberrant form«, which will be noted. 



The aniennce. They maybe filiform, flattened (^ ), compressed (9), 

 unipectinate, bipectinate, serrate, lamellate, or dentate, and smooth, ciliate, 

 fasciculate, or spinose. They generally differ between sexes of the same 

 species. 



The palpi vary in length of joints often between sexes of the same 

 species, but not between individuals of the same sex. Their position is 

 not given, since it is not always natural after death. The comparative 

 terms used to describe them may be thus limited as nearly as is possible : 



Short, when looking downward vertically their tips are not, or 

 are just visible beyond the front. 



Moderate, when ihey |)ruject beyond the front equal to the 

 width of it between the orbits. 



Lotig, when they exceed that limit. 

 The front a/ tubercles and tujts. 

 1 he tongue. 

 The claws on fore tibice. 



Veins J and S 0/ hind 7i'ings, the former by its presence or absence, 

 the latter by its connection with or separation from the discal cell, are 

 important divisors of families, as well as genera. 



March, 1907. 



