INTRODUCTION 7 
Malloch (1919) stated that most, if not all, of the calypterate 
flies have a longitudinal suture on the dorsum of the second an- 
tennal segment and that this suture, with minor exceptions, is 
absent in acalypterate species. In this paper Malloch also stated 
that the abdominal spiracles are located in the tergites in species 
of Calypteratae but are located in the membrane between the 
tergites and sternites in species of Acalypteratae. These char- 
acters have been found to hold with remarkably few exceptions, 
the most notable being pointed out by Malloch ina later paper 
(1925) when he erected the family Glossinidae for the species 
of Glossina (these have the abdominal spiracles located in the 
membrane, possibly owing to their pupiparous mode of reproduc- 
tion). These two characters alone will usually separate nearly 
all the calypterate species from the acalypterate species. Mal- 
loch also introduced many other characters hitherto unnoticed, 
such as the pilosity or bareness of the propleura, postalar de- 
elivity, prosternum, and posterior surface of the hind coxa 
(1918) ; later still he introduced others such as the form of the 
reniform greater ampulla (1925) and the presence or absence 
of intrapostocular cilia (1935), which he used to separate doubt- 
ful Tachinidae from certain Calliphoridae. In the last mentioned 
paper Malloch placed Silbomyia in the Tachinidae, but most of 
the specimens which I have seen have intrapostocular cilia and 
the form of the male genitalia is conspicuously calliphorid. Be- 
cause he introduced many such characters in the body of de- 
scriptions or in keys, the exact dates when some were first pro- 
posed are difficult to ascertain. 
Baer (1921) introduced the character of the ‘‘infrascutellum’’ 
to distinguish the Tachinoidea from the Sarcophagoidea. The 
same character was independently employed by Malloch in 1925. 
Shannon (1923 and 1926) again raised the blowflies to family 
status, and in the former paper separated this family from the 
Sarcophagidae by the presence of pile on the prosternum and 
propleura and a patch of setae on the metanotum below the 
squamae. These characters excluded the Polleniinae, but Shan- 
non included these in Calliphoridae in his second paper by giv- 
ing precedence to the character of the absence of hair on the 
posterior surface of the hind coxa, which is present on all the 
species of Sarcophagidae then known to him. 
In another paper Shannon (1924) pointed out that the pres- 
ence or absence of hypopleural bristles is closely correlated with 
the biologies of the major groups within the Calypteratae. He 
observed that groups lacking these bristles are mainly phyto- 
phagous in larval habits, while those groups which have hypop- 
