ox IXDIAX PARASITIC PLIES. 
709 
deposit it on the back of the caterpillar it would be much less certain 
of securing an attachment. The alarming size of the fly, the con- 
sequent frantic efforts of the caterpillar to shake off the maggot and 
the hairs which protect the back and sidis of the caterpillar with an 
almost impenetrable thicket, are thus circumvented. 
The maggots of this group are protected by a thicker and darker 
integument than the usual white and thin-skinned forms, since they 
have to pass a time exposed to the atmosphere. 
Tachinids form an enormous group of parasitic flies with wide 
geographical distribution. Over 300 genera have been established. 
Classification and nomenclature are in a state of flux. The Indian 
species have hardly been studied at all and must be very numerous.* 
Here is a rich and almost virgin field for Indian collectors and ob- 
servers. 
Muscidee and Sarcophagida'. Although most of the species in 
these two allied families are not parasitic at any stage of their exis- 
tence, others are always or occasionally parasitic as larvaj, and a few 
are blood-suckers in the adult stage. The frontier which divides 
these two families is undetermined. The Muscoidea are of extremely 
recent evolution ; in fact their evolution is still going on. In 
these two families we can see parasites in the making. It has already 
been pointed out that a promiscuous choice of hosts is evidence, and 
indeed a necessary result, of the recent origin of the parasitism. 
No fixed habits comparable with those of the Hymenopterous 
parasites are to be found in any parasitic Muscoidea except the 
(Estridee. 
Muscidee. To this family belong the only blood-sucking 
Cyclorihapha, other than Diptera pupipara if these latter are to be 
regarded as one of the cyclorrhaphous sections. The blood-sucking 
Muscids, which as everyone knows, are well represented in India, 
belong to the three sub-families following : 
(1) Philcematomyince : with a single genus and three species all 
Indian. 
(2) Stomoxydince : with some six genera and many Indian species. 
(3) Glossinince : with a single large genus : the African Tse-tse 
flies. 
These three blood-sucking groups contain perhaps some potential 
or embryo parasites. The pupiparous habit is highly developed in 
the last of the three ; and it is but a step to the Hippoboscidee with 
a completely parasitic life. 
The eggs of the Muscidee usually hatch in a day but sometimes larvee 
* Tliere is an excellent coloured plate (Plate LXVIII) of some Indian Tachinids, 
after Van der Wulp’s water-colour drawings in H. Maxwell Lefroy’s “Indian Insect 
I-#e ” Calcutta 1909. 
F. ^1. Van der Wulp’s “Catalogue of described Diptera from South .Asia.” The 
Hague, 1896, mentions under fifty Indian species and is otherwise far from perfect. 
