PARASITISM 
57 
1. Begin early to kill the flies that are seen. 
2. Remove all manure piles and make a general cleaning 
up of all refuse, thus destroying their breeding places. 
3. Put fly traps on the covers of garbage cans to entrap 
all those that hatch as well as adults that go in to feed. 
4. Keep many fly traps in operation in or about the house 
during the time of year that flies are active. 
5. Poison those that do come in the house and keep 
fly paper ready for them at all times. 
39. Tachina-fly. — This fly is beneficial to man. While 
it resembles the house-fly in appearance it has differences 
that may be clearly seen. It has long bristles on the abdo¬ 
men and the bristle of the antenna is bare. The tachina-fly 
lays its eggs on such larvae as tent caterpillars, army worms, 
and many other destructive caterpillars. After these eggs 
are hatched the tachina larvae bore into the bodies of the 
army worms or tent caterpillars and there feed until they 
consume them. Many kinds of caterpillars are held in 
check by the activities of these tachina-flies. 
40. Parasitism. — If a plant or an animal feeds on a 
living plant or animal, it is an example of parasitism. In the 
above, the tachina-fly is the parasite and the tent caterpillar 
is the host. The parasite feeds on the host. If it feeds on 
the outside of an animal, like the mosquito, it is called an 
external parasite. If it feeds on the inside of an animal, 
as in the case of the tachina-fly larva, it is called an internal 
parasite. Lice and fleas are external parasites. In some 
cases parasitism is helpful to man, as in the case of the 
tachina-fly; in other cases, it works harm to man, as in the 
case of the anopheles mosquito. 
SUMMARY 
The insects include a large number of animals, the smallest 
of which can be seen only through a microscope, while the 
largest, certain butterflies, measure nine inches across their 
