360 Prof, Mialland Mr. R. Shelford on the Structure and 
The dorsal abdominal projections consist of one pair 
on the sixth abdominal segment, which are curved, 
pointed, and directed backwards, and of two pairs on the 
eighth, which diverge from each other. Of these last the 
anterior pair are directed forwards, and are finely 
serrated on both margins; the posterior pair are turned 
backwards, and are serrated only on the anterior margin. 
A chitinous thickening which surrounds the segment con- 
nects them all together. On the ventral surface of the 
seventh abdominal segment isa pair of short, straight, and 
pointed processes, directed obliquely backwards. The 
last segment of all terminates in four small processes, 
two dorsal and two terminal; the dorsal pair are short 
and pointed, the terminal pair somewhat longer and also 
pointed. The processes of the eighth segment seem to 
serve for attachment; those of the sixth segment for 
maintaining the erect posture. Most of the segments 
show a division into three annuli, 
10. The imago. 
The perfect insect usually emerges in April, but one 
or more later broods may appear. ‘The males and 
females are about equally numerous. The fly is slug- 
gish, and does not travel far from the pool in which it 
was reared. 
IL. Hgg-laying. 
A female fly was observed to lay her eggs in a piece of 
moss. She crawled over the moss, inserting the 
extremity of the abdomen into the axils of the leaves, 
until about sixty had been laid. The moss selected is 
submerged. The eggs are laid singly, and adhere 
shghtly to the moss; they are dark-coloured, opaque, and 
spindle-shaped. The surface of the chorion is irregularly 
pitted. At one end is a rosette-like micropyle, which 
was found to be beset with numerous spermatozoa. 
12. Comparison with nearly allied insects. 
The larva of Cylindrotoma distinctissima, as described 
by Zeller,* bears some resemblance to that of Phalacro- 
cera. Unfortunately it has not been anatomically studied. 
* Tsis, 1842, p. 808. 
