This tribe contains many well-known insects--namely, the Midges, Gnats,
Daddy-longlegs, etc., which are divided into twelve families.
_Family 1, Cecidomyiidæ._--These are small delicate species, generally
clothed with long hair. They are all vegetable feeders, some of
them being very destructive to crops. The Hessian Fly (_Cecidomyia
destructor_) is probably one of the best-known species, on account of
the terrible mischief which it has caused in various countries, and
particularly in the United States of America. Miss E. A. Ormerod, the
well-known economic entomologist, has recently written a great deal
concerning this insect, with the view to preventing its increase in our
own country.
The Wheat Midge (_Diplosis tritici_) is another very mischievous
species.
[Illustration: Fig. 123.--Mycetophila Distigma (Mag.)]
_Family 2, Mycetophilidæ._--These are generally small species. They are
all vegetable feeders. The _larvæ_ live gregariously in fungi, rotten
wood, bark, etc.
The Army Worms (_Sciara_) of America, which belong to this family,
sometimes congregate in enormous numbers.
[Illustration: Fig. 124.--Macrocera Lutea (Mag.)]
The flies are remarkable for their remarkable powers of leaping.
_Family 3, Simuliidæ._--This family includes only one genus, _Simulium_.
It is, however, widely distributed, and some of the species, which are
popularly called Sand Flies, are exceedingly annoying in hot climates.
[Illustration: Fig. 125.--Simulium Ornatum (Mag.)]
_Family 4, Bibionidæ._--Several species belonging to this group are
very familiar insects. Among them is the St. Mark's Fly (_Bibio
Marci_), which is black, with transparent wings in the male and
brownish in the female.
These flies appear in the spring, and their _larvæ_ live in dung or
damp earth.