8 THE BLOWFLIES OF NortTH AMERICA 
leural bristles are mainly parasitic or carnivorous. He noted ex- 
ceptions to this generalization, but pointed out that most of the 
species with omnivorous larvae belong to the Muscidae, Callipho- 
ridae, or Sarcophagidae, and that in each of these species suffici- 
ent characters are available to indicate a common ancestry. Ac- 
cording to Shannon, the groups lacking hypopleural bristles are 
the more primitive in the two stipes, and it might be expected 
that they would have less fixed larval habits. He stated further 
that there are some omnivorous species of Sarcophagidae, but 
noted that most of the oestrid flies are obligatory parasites and 
that the relatively few instances of true parasitism on both 
invertebrate and vertebrate hosts among the anthomylid species 
are of independent origin. | 
Townsend (1935 and 1937) gave the first synopsis of the 
generic and supergeneric relationships of the ecalliphorid flies 
for the entire world. His work gives due consideration to all 
the previously introduced characters and proposes others per- 
taining to head structure, chaetotaxy, and the internal repro- 
ductive organs of both sexes. Biologies and the immature stages 
were also taken into account. In his Manual of Myiology 
Townsend has given us the most extensive work yet published 
upon the entire calypterate series, and his knowledge of the 
group exceeds that of any previous student. 
Since the genitalic structures of the various species of blowflies 
have been little used in supergeneric classification, a history of 
the use of genitalic characters as a means of specific differentia- 
tion has been omitted from the above discussion. The use of 
such parts as taxonomic characters is less than half a century 
old, but within the past 30 years an extensive literature has 
become available upon the specific differences of the genitalia of 
calypterate flies, particularly of the males. 
coated (1752) was probably the first Saratov: to 
describe and illustrate the internal sexual structures of Diptera.® 
Reaumur (1738), Suckow (1828), Dufour (1848), and others 
also described and figured parts of the reproductive organs of 
certain species. Siebold (1838) described the reproductive 
organs of Calliphora and Onesia. Lowne (1890-1895) described 
the reproductive structures of Calliphora and introduced much 
of the terminology of parts which is now in general use. Bruel 
(1898) also published upon these structures in Calliphora. 
Townsend (1908, 1911, and 1914) published significant contri- 
butions to the knowledge of the female NRE US System, He 
“Swammerdam’s ‘‘Bybel der Natuur’’ was not published until after his 
death, but was written previously to 1670. 
