Systematic Course. 45 
buties itself in the ground, where it transforms into alittle brown 
bean-shaped pupa, from which the fly afterwards issues. Tachinid 
flies are of very great importance on account of the wonderful effect 
which they have in keeping down defoliating caterpillars of all 
kinds, They are excessively numerous in India, and every single 
caterpillar which is parasitised by them perishes before it reaches 
the stage in which it can reproduce itself. They are also a 
serious nuisance to silk-rearers,and special precautions have to be 
taken to prevent their destroying silk-worms wholesale. 
In the case of the house-fly (Musca domestica) the eggs are laid in 
horse-dung and other decaying matter, and asa generation of the 
insect, under favourable circumstances, only takes about a fortnight, 
multiplication is excessively rapid. House-flies are believed to be 
frequent carriers of infectious diseases. We may also notice the mango- 
fly (Dacus ferrugineus, Fabr.), the peach-fly (Revellia persica, Bigot), 
and the melon-fly (Carpomyia parctalina, Bigot) which lay their eggs 
in ripening fruit, and occasionally do a good deal of damage in India. 
Another important species is the locust-fly (Authomyta peshawarensis, 
Bigot) which is parasitic upon the eggs of the migratory locust 
(Acridium peregrinum, Oliv.) of North-West India, and is believed 
to have a very considerable effect in keeping this destructive insect in 
check. The School Museum contains various specimens illustrative 
of the Muscide for examination by the students, 
Culicida.—Mosquitoes lay their eggs on the surface of stagnant 
water, The larve are active little aquatic creatures, with tracheal 
breathing organs at the posterior of the body. They are usually to be 
found in great numbers in dirty water that has been allowed to stand 
for a few days. ‘They are said to form one of the chief food supplies 
of young tank fish in India, and may possibly have some slight effect 
in preventing stagnant water from getting foul, as they feed upon the 
organic particles it contains. The pupe live in water and, unlike this 
stage in typical Diptera, have considerable powers of movement. They 
have respiratory tubes connected with their thoracic stigmata, through 
which they breathe air at the surface of the water. The female sucks 
the blood of mammals and birds and is said by some writers to be the 
host of the injurious Nematode blood parasite Filaria sanguinis 
hominis. The male has mouth parts unsuited for blood sucking, and 
is said to take no food during the imago stage. 
Under favourable circumstances mosquitoes can develop in about 
three weeks in India from the egg to the winged form, and as each 
female is capable of laying’ some hundreds of eggs, multiplication 
goes on excessively rapidly. Stocking tanks with fish is likely to 
tend to reduce the number of mosquitoes bred in the water. In the 
case of stagnant pools close to houses, which are too small to be 
