CONTROL OF BLOOD-SUCKING INSECTS                     33

Recently, Harris [1931], working in Natal, has introduced a type of trap
which, judging from the results reported to have been obtained from its use, would
appear to represent a very notable advance towards the formulation of measures
for the control of Glossina. The construction of the trap, as described by Harris,
is as follows : "It consists of a platform, 6 feet by 3 feet, across which is an
opening 6 inches wide, extending from side to side. Attached to the ends are
folding legs which taper from 3 feet in width at the top to 6 inches at the bottom.
The whole of this table-like shape is then covered with double hessian forming
a hollow bulk. The legs are kept apart by a wooden stretcher inserted between
them. Covering the 6 inches opening in the platform is a cage fitted with a non-
return passage through which the flies go, to become entrapped in the cage. The
trap is painted white and suspended from a wire about 3 feet above the ground
surface ". The habit of the fly which it has been sought to exploit in the cons-
truction of this trap is described as follows : " When they alight on the animal,
according to Mr. Harris, tsetse-flies crawl down towards the under parts, possibly
to get out of reach of the tail or muzzle, possibly in search of softer skin "
( Times Weekly Edition, March 26, 1931). The trap, therefore, would appear to hold
out very little prospect of proving successful for the purpose of combating
Tabanids, inasmuch as these flies are seldom observed to behave in the manner of
the tsetses as described above ; on the other hand, they would appear, as a rule, to
get engorged at the very spot where they alight on their host's body.

                                 (d) Traps for other Biting Insects.

For the control of fleas, Delanoe [1922] recommends the use of a fairly large
receptacle containing water covered with oil. In the centre of this receptacle a night
lamp is placed, and the fleas are stated to be attracted to the light and get drowned
in the oil. In one locality in Morocco, about 300 fleas are reported to have been
entrapped by this method. The same author [1922] mentions live sheep as being
quite a practicable trap, as the wool asphyxiates the fleas. Further, Delanoe
quotes Weisgerber as having stated that a sheep skin, even if washed, can be used
as a flea trap, the reason being probably that the flea is held captive by the hairs.

The control of the minute species of blood-suckers, such as sand-flies (Phleboto-
mus) and the midges, is a matter of considerable difficulty. However, Cathcart
[1923], in Iraq, records having obtained good results in attracting and destroying
sand-flies, by the use of hurricane lamps smeared with vaseline.

                                     (e) Traps for House-flies.

Several methods have been recommended for entrapping the larval forms of
Muscidæ, but as a consideration of these methods would have but little bearing