VETERINARY ENTOMOLOGY FOR INDIA                  193

    The presence of water is necessary for the majority of Tabanidae, so that dry
and arid tracts are inhabited only by some rare—evidently migratory—species
[Seguy, 1924]. According to Surcouf [1921] the regions that have yielded the largest
number of Tabanids, both in respect of genera and species, are those that enjoy
a moderately elevated temperature and possess some forests or mountainous reliefs
with water and a varied fauna. Galli-Valerio [1930] says that the abundance of
Tabanids does not depend on the presence of cattle, but varies with the year and
the place, for Tabanids leave their normal habitats only if man and animals pass
through them, when the flies may follow them for long distances. In most localities
in India, Tabanids are common during the Rains, the adult females and occasionally
the males visiting human habitations where they may be seen on the walls and
window panes, sometimes even attacking the occupants.

    The females only are blood-suckers, the food of the males consisting of the
nectar of flowers, the sap oozing from plants and frequently the sweet juice of over-
ripe fruits dropped on the ground [Surcouf, 1924]. Williston [1908] says that the
females also feed on the honey-dew secreted by plant-lice and scale-insects and on
similar substances. As originally observed by Portchinsky and later confirmed by
other observers, several species of Tabanidae have the curious habit of swooping
over the surface of pools and other collections of water, evidently for drinking
purposes. The females are almost exclusively parasites of warm-blooded
animals, their usual hosts being horses, cattle, mules, buffaloes, camels, elephants
and sometimes man. Surcouf [1923] refers to certain genera of Tabanids
(Adersia, Brodenia and Lesneus) which in their adult stage have the appearance of
Œstrids and which do not appear capable of taking nourishment on account of the
extreme reduction of their buccal apparatus, so that, like the Œstridæ, they
probably live as parasites in their larval stages. Members of these genera,
however, are not known to occur in India. It is relatively simple to capture the
females while they are in the act of sucking blood or ovipositing, but the males are
relatively seldom seen ; they may sometimes be swept with a net from grass and
other vegetation or noticed at rest on tree-trunks or walls.

    To those having to deal with stock under field conditions in India, the Tabanids
are conspicuous by reason of their relatively large size and the severity of their
bites, it being not unusual to observe blood freely flowing from the wounds inflicted
by them. This is often accentuated by the large number of individual Flies which
attack. It is not unusual to be able to catch fifty or more Tabanids on one animal
in an hour.

    The different species of Tabanids have a curious predilection for the site in the
host's body from which to feed. Thus, according to Patton and Cragg [1913], in

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