Kinsey: The Genus N euroterus 
9 
down with repetitions of generic characters. The understand- 
ing of the species will be possible only when related forms 
are directly compared, when one will accept a paucity of 
distinctive characters, and when every possible sort of avail- 
able data is utilized. 
In the external anatomy of the insects of N euroterus, 
the total number of separate characters which show distinct 
variation between species is nearly 50. This includes all 
the characters that any student has ever used except a few 
which are to be measured only by inconveniently refined 
methods or which are so microscopic or hidden as to be un- 
available without dissections. The use of comparative de- 
scriptions makes it possible to readily count the average 
numbers of the characters which vary in particular groups. 
50 vary in the genus. 
27 vary in the subgenera. 
17 vary in species of Dolichostrophus, 
10 vary in species of Diplohius. 
9 vary in varieties of N eospatheg aster . 
7 (4-10) vary in varieties of Dolichostrophus. 
5 (4-7) vary in varieties of Diplohius. 
These statistics must be considered approximations, for 
it is to some degree a matter of individual opinion as to what 
constitutes a distinct character, and further the differences 
in magnitudes of the several characters affect their impor- 
tance. Nevertheless, several generalizations are evident. 
Altho a large number of variable characters are available, 
only half the number varies even between subgenera, and 
a very small number vary in any lower category. A taxon- 
omic group must not be recognized in whole by the relative 
number of its variable characters, but here is some evidence 
that in this genus the degree of similarity of varieties, for 
instance, is about double the similarity of species, and species 
are twice as similar as subgenera. It is noteworthy that both 
the species and varieties of the subgenus Diplohius are 
distinctly more similar than those of the related group 
Dolichostrophus. 
These figures give only the total numbers of variable 
characters ; an examination of the particular characters shows 
that practically all of them may at times vary, some varying 
in one species or subgenus, while entirely different ones are 
