1941] 
Male Diptera 
83 
illustrated by the Helomyzid Neoleria crassipes shown in 
Fig. 7, in which the relative proportions of the segments are 
essentially those characteristic of the typical Muscoid flies 
next to be considered. The fifth segment is practically un- 
modified, the sixth tergite, 6t, retains its normal position, 
but its asymmetrically developed sternite, 6s, is lateroverted 
and becomes attached by one corner to the lateroverted 
seventh sternite, 7s, which, in turn, is attached by one corner 
to the inverted eighth sternite, 8s. The left spiracle of the 
seventh abdominal segment is displaced dorsad, but is not 
enclosed in the sclerites behind it. 
A higher stage of specialization is illustrated by the 
Muscid Hylemya antiqua shown in Fig. 20, in which the 
parts bear essentially the same relations to each other as 
they do in Fig. 7, save that the seventh sternite, 7s, has now 
become adherent to the eighth sternite, 8s, from which it is 
demarked by an incomplete suture ; and the left spiracle of 
the seventh segment is now borne in the anterior region of 
the composite sclerite made up of the lateroverted seventh 
sternite and the inverted eighth sternite (with which the 
reduced seventh tergite may also have united, although the 
fate of the seventh tergite cannot be definitely determined 
from the available material) . 
We may speak of the composite sclerite made up of the 
uniting seventh and eighth sternites (7s and 8s of Fig. 20) 
as a synsternite, to denote the fact that it is composed of the 
sternites of more than one segment, although it is usually 
spoken of as one “segment,” called the first genital “seg- 
ment, while the ninth segment is then called the second 
genital segment. The so-called second genital segment, 
(or ninth abdominal segment) of the Muscoid flies is called 
the andrium in lower insects, while its sternite is called the 
hypandrium and its tergite is called the epandrium; and 
these terms might also be applied to the parts in Muscoid 
flies, in which the term protandrium might then be substi- 
tuted for the designation “first genital segment,” which is 
not a single segment but is a composite synsternite. 
The slender curved sixth sternite 6s of Fig. 20 supports 
a genital pouch, or cubiculum, in which the anteriorly 
directed aedeagus, ae, is received in repose, and this type of 
structure is typical of many Muscoidea. The fifth sternite 
