29 
So far as our own fauna is concerned, the species are too nearly 
related to one another, both structurally and also in regard to their 
habits, to permit of being separated into smaler groups with any 
degree of satisfaction. 
TERMS USED IN DESCRIBING TACHINID At. 
Only a few terms employed in the present work will require an expla- 
nation, since in most cases the terms used in designating the various 
parts of the specimens are the same as those employed in the other 
departments of entomology. The term macrochetew is used to desig- 
nate the stout bristles which arise from a convex and usually polished 
base; they are regularly arranged in pairs, rows, or otherwise, and 
afford excellent specific and sometimes even generic characters. The 
frontal bristles are composed of two rows of such macrochietie, which 
descend from the very top of the head to or below the insertion of the 
antenne. The ocellar bristles are composed of a pair of macrochiete 
placed among the ocelli, but they are absent in several species. The 
orbital bristles are two or more pairs of forwardly directed macrochietie, 
situated between the frontal bristles and the eyes; they are usually 
present in female specimens, and sometimes also in the males. Beneath 
the antenne is a cavity known as the facial depression, bounded on 
the sides by the facial ridges; at the lower ends of the ridges is a 
pair of macrochetie called the vibrissa. The cheeks are between the 
lower ends of the eyes and the opening of the mouth. The antenna, 
as well as their two arista, are always composed of three joints, but 
sometimes the basal joint is extremely short. 
On the thorax the two rows of macrochetie in the middle of the 
dorsum are known as acrostichal, and the next two rows are the dorsal, 
although these four rows are sometimes called the dorso-centrals; these 
rows usually extend the entire length of the thorax, those in front of 
the transverse suture being called the presutural and those behind it 
the postsutural; but when the latter term is used in the accompanying 
pages it applies to those in the outer rows only. The row on either 
side of these four is called the intra-alar; this row sometimes extends 
in front of the transverse suture by a single macrocheta, which has 
received the name of the presutural intra-alar bristle. One European 
author, Mr. Girschner, proposes to separate the Tachinidie into two 
groups according to whether this bristle is present or absent, but in 
some of our species it is present in some specimens but absent in others 
that belong to the same species; this character, therefore, is not of 
specific, much less of subfamily, importance. The sternopleural macro- 
chet are situated on the upper part of the transverse, more or less 
triangular, piece located on the sides of the thorax between the front and 
middle cox; when only one is present, this is the posterior; when two, 
these are the anterior and the posterior; when three, two are in front and 
one behind; and when four, these are in a downwardly curving row. 
Lhe macrochetse on the dorsum of the abdomen are called discal 
