Structure and Life-history of the Holly-fly. 279 
within the tube-like 7th segment. ‘The muscles effecting 
this retraction arise from the inner surface of the chitinous 
extension of the 7th segment, and are inserted into the 
9th segment, some at its beginning and some further back. 
Alimentary Canal.—The general arrangement is similar 
to that of the larva. The salivary glands (fig. 13) persist, 
but are much reduced in size. The posterior part of the 
cesophagus gives off a median ventral diverticulum. This 
passes back through the thorax as a narrow tube lying 
below the stomach, and dilates in the abdomen into a 
very distensible thin-walled sac, which corresponds to 
the sucking-stomach of other insects. As the pharyngeal 
‘Gao 
\ SS 
COPS 
sco USPS oe 5 Pag ee 
Fie. 19. 
Posterior abdominal segments of female fly, diagrammatic. The ovipositor is 
retracted into the 7th segment. 
pump no doubt serves to draw fluids into the mouth, it is 
rather uncertain what is the special function of the sucking- 
stomach. The rectum dilates near its beginning into a 
pyriform chamber, the wall of which is provided with 
four papille. 
The Heart.—The heart (fig. 13) lies in the dorsal part 
of the abdomen. It is widest in front, where it abuts upon 
the posterior surface of the mesothoracic wall. From its 
anterior end a fine tube passes downwards and enters the 
thorax, lying along the dorsal surface of the stomach (this 
thoracic portion is not represented in fig. 13). Ostia occur 
in the first five abdominal segments. 
The Ovary.—The paired ovary (fig. 13) consists of twelve 
to fourteen tubules, which are connected at their base with 
the oviduct. The two oviducts unite to form the 
uterus, which opens ventrally between the 8th and 9th 
TRANS. ENT. SOC. LOND. 1907.—PaRT Il. (SEPT.) 19 
