4                                    Surra.

at the lower stages. After the rains commence these flies
soon disappear, and the first case of Surra in 1907 is said to
have been observed when they were becoming scarce. None
of these flies were to be found at the time of investigation.

A Stomoxys which sucks the blood of horses and bullocks
is present throughout the hot weather and disappears towards
the end of October, when, as a rule, no further cases of Surra
occur. It is to be found at every stage on the line. At night
they collect on the leaves of trees and seem to have a prefer-
ence for a tree locally known as " Simal. " They bite all parts
of the body but particularly the fore legs below the knee. A
Hippoboscus is also present at every stage during the same
period, but in much smaller numbers. It is to be seen at com-
paratively high altitudes over 5,000 feet and is found on horses
both during day and night.

At Bojiaghat and Kathgodam, horses, bullocks and buffa-
loes were observed to be severely bitten by some insect
at night time. Late in the evening it is usual to find a few
small fresh blood clots on the hairs of these animals. Early
in the morning, before the Stomoxys commence to bite, nu-
merous dry clots are found attached to the end of hairs on most
parts of the body. Of the pony the withers and back are most
attacked and even in the buffalo the thickest part of the hide
is penetrated. These blood clots are very distinctly seen
on a white or grey pony in the morning.

That these clots were not caused by the Hippoboscus was
concluded from the fact that few of these flies were found in
the stables at nights. The bites occurred to a lesser extent
when the ponies were rugged. The Hippoboscus was never
found on cattle or buffalo.

Many visits were made to the stables at night in order
to discover the cause of these blood clots. An insect resem-
bling a small mosquito* was found in large numbers on the
ponies, but it did not appear to be a blood sucker, as no trace
of blood was found in the stomach after many examinatinns.
Other mosquitoes were present in small numbers, but none
could be secured while biting either ponies or bulls. The syces

* Classified by Dr. Austen as a Phlebotomus (new species) Flies Classified by Dr.
Austen, see page 15.