324 DR. A. E. SHIPLEY ON [ Mar. 16, 
stated above, we believe to be S. stercoraria, may eventually turn 
out to be a local variety. 
The larva of the fly has the usual maggot-like shape, tapering 
from behind forward towards the mouth. Counting what appears 
to be the cephalic segment—but which in reality probably repre- 
sents more than one segment, and which is thus conveniently 
called the ‘ pseudo-cephalon ” *—as one segment, there are thirteen 
in all, the usual number for Dipterous larvee (Pl. XLV. fig. 26). 
The cuticle is thin, the maggots are white. ‘They bear numerous 
small spines which are especially conspicuous in a ring around 
the anterior end of each segment. These rings emphasize the 
segmentation of the larva. 
The ‘pseudo-cephalon” is pointed, and varies in outline 
according to how much of the mouth and its sclerites are pro- 
truded or not. These sclerites are the most conspicuous structures 
in the larve; jet-black, they stand out against the white tissues 
of the maggot. There is a pair of hooks which apparently 
correspond with the single median mandibular sclerite of Musca 
domestica. At the base of each of these is a dentate sclerite, 
and behind the mandibular sclerite articulates with the hypo- 
stomal sclerites. These latter are irregular longitudinal bars 
connected by a slight transverse plate on the ventral side. In 
M. domestica the salivary glands open into the pharynx just 
in front of this transverse piece. Posteriorly the hypostomal 
sclerites are very closely articulated, or perhaps even fused with 
the large lateral pharyngeal sclerite. This consists of a ventral 
plate, continuous with two lateral plates which are deeply notched, 
and in the house-fly the nerves and tracheze which supply the 
pharynx enter through this notch. The two lateral plates are 
united anteriorly by a dorsal cross-piece. The whole of these 
sclerites are being continually pushed forward and retracted by 
a complicated series of muscles which have been carefully described 
in the case of MW. domestica by Dr. C. Gordon Hewitt (Pl. XLV. 
fig. 27). 
The mouth is bordered by tumid lips, above which the hook- 
like mandibular sclerites are pulled and pushed in and out. 
Dorsal to these again are two elevations which each bear two 
sensory papille; these correspond with the sensory tubercles of 
AW. domestica, though the latter are not borne on an elevation. 
The anus opens on the truncated thirteenth segment, well 
forward on the ventral surface ; around it, symmetrically placed, 
are four anal papille, which assist in the movements of the 
maggot (Pl. XLVI. figs. 31 & 32). 
The tracheal system opens on the flattened posterior end, about 
the centre. Ventral to the stigmata there are two or three 
pairs of low papille. Hach stigma leads into a trachea, which 
almost immediately splits into a visceral branch (Pl. XLV. fig. 26) 
which bends down into the viscera and extends a little way in 
* Henneguy, L. F., ‘Les Insectes,’ Paris, 1904. 
+ C. Gordon Hewitt, Quart. J. Mic. Sci. lii. 1908, p. 495. 
