ON JNDIAN PAliASniC FLIES. 
711 
by their red eyes and grey thorax striped longitudinally with black. 
They are thick-set flies of moderate size and frequent the neighbour- 
hood of decaying animal and vegetable matter. The known Indian 
species nearly all belong to the genus Sarcophaga and the commonest 
Indian species is probably S. Imeatocollis Macq. In Gujarat it is 
not uncommon to see large sores on the human scalp full of the larvae 
of a species of Sarcophaga ; whether such larvae truly deserve the name 
of parasites depends on how far this method of nutrition is an estab- 
lished and regulai habit. 
(Estridee. The flies of this family are sometimes included among 
Calyptrate Muscoids but are best regarded as a distinct group which, 
has arisen from several Muscoid types and now is much specialised 
for a parasitic life. They form a small and well defined group with 
about seventy or eighty desciibcd species scattered over the world. 
The larvae are always parasitic on mammals and on mammals only. 
The hosts of the Indian species are horses, sheep, cattle, elephants, 
rhinoceroses and camels. The note-worthy feature in the life history 
of an CEstrid fly is that feeding is confined to the larval 
stage. This is the parasitic period when the growing insect lives 
surrounded by nourishment. 
Parasitism of the larval insects takes three principal forms. We 
have parasities (1) in the food canal, (2) in tumours formed by the 
larvae under the skin, and (3) in the normal cavities of the nose and 
throat. It is a general rule, with but few exceptions, that each species 
of CEstrid fly is confined to a single species of mammal ; and allied 
species of fly are parasitic in the same fashion upon allied mammals. 
The adults are free-living, large, hairy flies, which take no food 
and exist only for procreation of their species. The adult fly 
has a minute mouth and often such atrophied vestiges of mouth, 
parts that it is incapable of taking any food. Nevertheless some of 
these flies live for three or four weeks and display great activity. 
Brauer classified the CEstridee according to the combined characters 
of the larvae and the perfect insects*. He divided the typical 
CEstrids into three groups, which ^coincide with a classification based 
on the parasitic habits of the larvae. His three divisions are the 
following : — 
1. Gaslricolce. Larvae found in the stomach and gut of Equi- 
dae (Horses, asses, etc), Bhinocerotidee (rhinoceroses) and Probos- 
cidea (elephants). To this group belong Gastrophilus, Gyrostigma 
and Cobboldia which are all three Indian genera. 
* Profe.ssor Friedrich Brauer of Vienna brought out his monograph in 1803. .1/o- 
nofjraphie der CEslriden, by Friedrich Brauer. Wien, 1863. It was an epoch-making 
work ami contains a complete bibliography of all the literature on the (Estridm 
up to that year. It is still a standard authority in spite of much recent work on t! e- 
group. See also “ Nachtrdge zur Monographie dir CEslriden ”, Wiener Eniom. 
Zeitung, (1887) vol. VI., p.4. by F. Brauer. 
18 
