384 
Annual Report for 1913 of the Zoologist. 
to. have a beneficial effect. Theoretically any time in the 
winter might be selected for such treatment, but probably the 
larvae are more vulnerable immediately after descending to the 
ground and before they have thoroughly established themselves 
in their winter quarters. 
Animal Parasites. 
In May a remarkable plague of “ sand-flies ” occurred in the 
Lake District. These insects, though often a nuisance on a 
small scale, very rarely occur in such prodigious numbers in 
this country as to be a serious pest as they often do abroad, 
especially on the banks of the Danube and in North America. 
In the present case the flies seem to have been more or less 
troublesome for two years past and this year they were so 
numerous that, in the words of my correspondent, i( dogs 
suffered much ; the bellies and udders of cattle were black with 
them ; children came in with their faces covered with blood, 
and they got up sleeves and trousers and down the neck so 
that no part of the body was safe from them.” 
The flies are small, black insects, belonging to the genns 
Simulium , and called in America u buffalo gnats ” from the 
humped appearance of their backs. They are not to be con- 
founded with the true gnats or mosquitoes, nor with the 
“ midges ” ( Ceraiopogon ), so troublesome, especially under 
trees, in the summer. The trouble is that instead of breeding 
in stagnantwater ponds, puddles, water-tanks, &c., like the gnats, 
they live as larvae in the clear water of lakes and rivers. The 
measures which have proved so successful against mosquitoes 
are, therefore, of no avail against these flies, and there seems to 
be little to be done except to dress the cattle with some prepara- 
tion calculated to warn them off and to hope that their natural 
enemies will soon come to our assistance. 
Mr. Austen, of the British Museum, identified two species 
as concerned in the present plague. 
As usual, . several applications having reference to the 
diseases of animals had to be referred to the Meterinary depart- 
ment. Among the most frequent were complaints of stomach 
worms in sheep, which cause great annual loss and are most 
difficult to treat effectually because of the uncertainty that any 
di ug administered will reach the fourth stomach, where the 
worms live, in an unaltered condition. The whole subject is 
being investigated by Mr. Pethybridge at Cambridge, and it is 
hoped that some light will be thrown on the sources of infesta- 
tion and possible methods of prevention. 
Observations on the warble-fly last summer confirmed the 
view that the eggs are not laid on the back of the cattle but on 
the hairs on the legs, and this supports the conclusion, arrived 
