112 Bulletin of the Brooklyn Entomological Society Vol. XIV 
who are not conversant with the species as a whole, and give as 
little latitude as possible to individual opinion, so reducing prob- 
ability of error to a minimum. 
The standard indicated is a rather high one and undoubtedly 
very difficult of attainment, but in the case under consideration 
it is possible by the use of one character to separate nearly all 
of the calyptrates, including Scatophagide, from the other cyclor- 
rhaphous Diptera. This differentiating character is the position 
of the abdominal spiracles. In the calyptrates these are situated 
in the tergites, while in the acalyptrates they are situated in the 
conjunctiva, or membrane between the tergites and the sternites. 
There are very few exceptions to this rule, those in the former 
group being present, so far as I know at present, in Gastrophi- 
line, and a few males in the Scatophagide and Fanniinz, while 
in the acalyptrates the exceptions are met with in some genera of 
Ephydridz and in a few species of Dryomyza. The second an- 
tennal joint of all calyptrates has a longitudinal split on its upper 
outer surface which usually extends to or nearly to the base, a 
feature rarely present in any of the higher acalyptrates. Acces- 
sory characters for the differentiation of the groups are found in 
the venation of the wings, and the tibial armature. The outstand- 
ing fact developed by accepting the tergal spiracles as the differ- 
entiating medium is that the Scatophagide belong to the calyp- 
trate series, a conclusion which is borne out by their larval 
characters. 
_ That the position of the abdominal spiracles is of primary 
importance in classifying mature insects is beyond question, as 
may be proven by an examination of forms belonging to the 
various orders, the most generalized forms having them situated 
in the sternites, while the most specialized have them in the 
tergites. A striking instance of this specialization is seen in the 
family Cyrtide, the larve of which live as internal parasites in 
spiders, where the species have so far I have seen tergal spiracles, 
the other Brachycera examined by me having the spiracles in the 
conjunctiva. 
