50 THE BLOWFLIES oF NortH AMERICA 
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gonapophysis (AC) (here called the anterior clasper) has a wide 
base which is fused to the under surface of the quadrilateral 
plate. The ventral edge is often ornamented. The posterior 
gonapophysis (PC) (here called the posterior clasper) is usually 
a stout, elongate plate which is often heavily sclerotized at the 
base but less so apically. The ventral surface may also be or- 
namented. The shape and ornamentation of these parts are 
sometimes of specific importance, but the perspective from which 
the plates are viewed often distorts these characters. 
The inner forceps (IF) and the outer forceps (OF) are the 
hindmost genital appendages. The inner forceps lie on each side 
of the anal opening or slightly below it. These articulate at their 
bases with the outer side of an inner distal process of the second 
genital segment. Just anterior to these are the outer forceps, 
which articulate basally on the outer side with an inner distal 
process of the second genital segment and also with the inner 
forceps at their bases. Basally and anteriorly, these forceps ar- 
ticulate with the posterior end of the basal plate of the outer 
forceps which unites the forceps and the vinculum. Both the 
inner and outer forceps afford characters which are often visible 
in some degree without special preparation. The inner forceps 
may appear hook-like in profile, the outer foreeps — andr more 
pad-like. 
Internal sexual organs of male. The ‘teen sexbal organs of 
the male blowfly (Fig. IV) consist of a pair of testes (T), one on 
each side in the posterior portion of the fourth abdominal seg- 
ment, their ducts (VE) (vasa efferentia), a pair of vehicular 
glands (VG) (paragonia), an unpaired vas deferens (VD), an 
ejaculatory sac (ES), and the ejaculatory duct. 
In the various species of Calliphoridae the testes are usually 
pyriform, often with an hour-glass constriction at the lower 
third (which apparently acts as a pump), surrounded by an 
envelope of fat cells, and extending into a short vas deferens. 
The vehicular or accessory glands open by means of a very 
short duct and accompany the distal ends of the vasa efferen- 
tia into the vas deferens. The latter usually tapers gradually 
for about half its length into a tube of more or less uni- 
form diameter which opens into the ejaculatory sae or bulb, 
from which the thin and extensile ejaculatory duct passes to 
the terminal portion of the phallosome. 
The testes in Pollenia (Polleniinae) are long subpyriform and 
taper distally. In Rhyncomyia (Rhiniinae) they are fusiform 
in thick hoods of tissue. In Callitroga (Chrysomyinae) males 
have testes that are more or less elongate and also in tissue hoods, 
