i2o THOMPSON YATES AND JOHNSTON LABORATORIES REPORT 
The larva possesses slight inconspicuous spines at the joints of the segments. 
On the anterior segment it is marked with pits, while elsewhere there is a 
reticular pattern. 
On the terminal bulbous segment of the larvae are situated two beautifully 
adorned structures, the openings of the respiratory syphons (Fig. i). These are like 
two discs without any perceptible stalk, with the margin turned slightly downwards. 
The inner portion is marked by a beautiful convoluted (chitinous) yellow marking 
(peritreme), which is interrupted atone point, and in the larvae examined the interruptions 
in each convolution are at corresponding points, so that they face each other. In the 
larger larvae this convoluted arrangement could not be clearly traced, and a central 
dark area of the discs noticeable in the large larvae was absent in the small. In the 
larger larvae the syphon seemed to consist of a disc, on which was situated a little 
mole hill (area of convoluted marking), and in this was a small central crater (Fig. 4). 
On the anterior end of the larvae could be made out a pattern of more or less 
elongated spaces passing round the larva. 
The larvae of Musca corvina are then characterized by 
1. The single hook. 
2. The polygonal areas (seen anteriorly). 
3. The lateral respiratory appendages with their eight processes. 
4. The posterior respiratory syphons (2) with their convoluted tracings. 
Larva of Homalomyia canicularis. 
They differ much in appearance from the former. They are of a brownish 
colour, about 6 mm. in length, pointed at the anterior extremity and rounded 
posteriorly (Fig. 1). They have a dorsal convex surface and a flattish ventral 
surface. To the naked eye they appear' hairy. On examination with a low power 
of the microscope the larva is seen to possess thorny appendages on each segment. 
There are two sets of main appendages — a dorso-lateral and a ventro-lateral pair on 
each segment. The dorsal pair of hairs are somewhat coarse and longer than the 
ventral pair. Further, on the true dorsal surface between the dorso-lateral hairs 
exist a short pair of central hairs on each segment (Fig. 2). The hairs are attached 
in the hind segments to the posterior margins of the segments, but, as we proceed 
anteriorly, they shift their position gradually, so that in the anterior segments they 
are attached to the anterior margin. The hairs, on examination, are seen to be 
markedly spinous (Fig. 2), coarse at the base, decreasing in size towards the tip, and 
there are about twenty main thorns on each process. They are arranged in two 
rows — anterior and posterior. 
The lateral margin of the segments, from which the hairs proceed, are also 
coarsely spinous. Besides these principal segmental appendages, there are the smaller 
spinous dorsal hairs already mentioned, but we also have between these and the lateral 
