ox IXDIAX FABASITIG FLIES. 
705 
^ouping becomes in a large measure a true and natural one though 
not founded on the ordinary taxonomic characters. 
The ten groups are as set out below : 
1. Species which glue a short flattened macrotype egg to the 
host’s body. 
2. Species which deposit on the food of the host a microtype 
egg containing the developed maggot and destined to be swallowed. 
3. Species extruding large and strong larvae known as ordinary 
flesh maggots. 
4. Species which deposit maggots (naked or in choria) in the 
path of the host. 
5. Species which deposit maggots (naked or in choria) probably 
in the neighbourhood of the host. 
6. Species which deposit maggots (naked or in choria) on the 
body of the host. 
7. Species which introduce into the host’s body maggots (naked 
or in choria) by means of separate instruments of perforation and 
injection. 
8. The same but by means of a combined instrument to perforate 
and inject. 
9. Species destitute of incubating apparatus but provided with a 
variable chitinous ovipositor for introducing the undeveloped eggs 
into the host. 
10. Species which deposit on the host a pediceled egg in which 
the maggot is already well developed. 
Examples of most of these groups will be met with in the five 
families now to be dealt with. 
Taohiiiidce and DzxiiicB. The habits and life histories of these 
two families are so much alike that the) can be treated together. 
The Dexiidce closely resemble the Tachinidce. Willistone consi- 
ders that the distinction between the two families is very difficult 
to make, if it be not actually evanescent. Townsend lumps most 
of the old Dexiidce with the Tachinidce. Both are smallish to fair- 
sized hairy flies with strong legs and conspicuously large squamae. 
The habits of the mature Tachinid flies are much the same in all the 
members of the group which is a large one. They are found on plants 
and on leaves or flowers which are the haunts of the hosts which they 
seek to parasitize. So far as is known all the larvae are parasit.c 
in habit and the parasitism is confined to the larval stages of other 
insects. The individual female Tachinid is not always particular 
in the choice of the species of larvae which she parasitizes. 
In the Muscoidean flies the integument is furnished with many 
large bristles called machrochaetce. In the Tachinidce this hairiness 
is most characteristic and is of some interest in connection with their 
parasitic habits which involve running about and searching for 
caterpillars. Osten-Sacken has pointed out that these bristles occur 
