INTRODUCTION 9 
was apparently the first to appreciate the taxonomic importance 
of the female genitalia of Diptera. Patton (1932-1939), together 
with certain of his students (E. C. Cushing and Chi Ho), has 
published extensively upon the external structures of the male 
and female genitalia of certain muscoid flies. His conclusions are 
that these parts are of considerably more importance in the 
ultimate classification of such flies than has hitherto been 
attributed to them. 
With the sole exception of Townsend’s papers on the female 
reproductive system, however, there has been little or no attempt 
to use the internal sexual organs as a means of indicating rela- 
tionships of such flies. 
Pandelle (1896) described the male genitalia of a number of 
Palaearctic calypterate species. He gave no illustrations and his 
descriptions of such parts were little used by later students. 
DuRoselle (1904) in Europe and Lahille (1907) in Argentina 
illustrated the male copulatory organs of several calypterate 
species, these illustrations being intended for use as an aid for 
the identification of the species involved. Boettcher (1912-1913) 
published a synopsis of the Palaearctie species of Sarcophaga 
and used the male genitalia as a means of specific determination. 
In this he was followed by Parker (1914) and Aldrich (1916) in 
North America. The use of the male genitalic structure as a 
means of specific determination in muscoid flies has become wide- 
spread since that time. Too often other available characters 
have not. been used in descriptions, and the result has often 
been that females cannot be accurately associated with their 
males. Furthermore, the grouping value of such characters has 
not been considered. Many contributors have figured genitalia 
without any attempt to evaluate the characters and have neglected 
to describe other essential details of the species. 
As new forms are discovered, characters previously introduced 
to separate larger groups of species become obscured. Thus, 
while Shannon endeavored to maintain the Calliphoridae as a 
distinct family, Aldrich indicated to the author (in lott., 1926- 
1928) that, on the basis of the same characters used by Shan- 
non, he regarded ‘the Sarcophagidae and Calliphoridae to 
be but one family, the Calliphoridae. Malloch (1925) had already 
indicated that he considered the Sarcophagidae to be a subfamily 
of the Calliphoridae. Curran (1934) proposed the name 
Metopiidae for the combination known to Malloch and Aldrich 
as the Calliphoridae. 
The furrowed dorsum of the second antennal segment, the 
presence of hypopleural bristles, the undivided metanotum, the 
