G. S. Graham-Smith 
523 
and the next day the chelifer appeared to be dead. The house-fly 
caught on Oct. 20 with one chelifer attached to a leg was also kept in 
a glass box. On the following morning the chelifer dropped off, but 
towards the evening it attached itself again. During the second night 
it left the house-fly and attached itself to the leg of a Stomoxys, which 
had been placed in the same box. It remained in this position till the 
Stomoxys died about 36 hours later, and was still attached in the same 
position some hours after its death. 
It was noticed that the chelifers occasionally came off when the flies 
to which they had been attached were confined in glass vessels. Some¬ 
times this appeared to be a voluntary act on the part of the chelifer, 
but on other occasions the fly got rid of the chelifer by means of its 
legs. The fly most commonly succeeded in detaching the chelifer 
when it got into a confined space, and was able to use its legs with 
greater effect than under natural conditions. Usually the detached 
chelifer made no attempt again to seize the fly though the fly often 
passed over it. When undisturbed it often walked forwards swaying 
its pedipalpi from side to side, and sometimes opening and shutting 
the claws, but occasionally stopping and bringing one of its claws to 
its mouth. At the approach of the fly it either ran backwards rapidly, 
or remained quite still. When touched by the fly’s legs it seemed to 
be greatly irritated. On two occasions, however, detached chelifers 
were seen to seize the legs of flies. The movement was very rapid, 
the chelifer appearing to spring towards the fly’s leg as the insect was 
approaching. 
All interested in this subject should consult Ivew’s (1901) interesting 
paper. 
Parasites of fly larvae and pupae. 
During the autumn of the year 1914 flies were allowed to deposit 
their eggs on the carcases of small animals. Some of these carcases 
were allowed to remain undisturbed on the ground through the winter 
in an outdoor cage, and others, laid on earth, were placed in two large 
galvanised iron receptacles into which flies could enter freely. One of 
these iron receptacles was kept in an open situation, where it was 
exposed to the extremes of heat and cold, and the other in a shady 
protected situation, where it never became very hot. These may 
be called the “Sun and Shade Tins” respectively (see p. 442). In 
the winter the minimum temperature recorded in the “sun tin” was 
usually about 1-2° F. below that in the “shade tin” ; on the other hand 
Parasitology vm 34 
