THE MYCETOPHILIDA:. 105 
b. Brachial vein and cubital forming a petio- 
late fork. 
a. Base of this fork is nearer to the base 
of wing than is base of second. hind 
areolet. Ditomyia. 
6. Base of this fork is more distant from 
base of wing than is base of second 
hind areolet. Plesiastina. 
The other three British sub-families only contain a single genus. 
The above synopsis is compiled from Winnertz, whose knowledge of 
the Mycetophilide is unequalled, although, as we shall see, very 
much has recently been done in Russia, especially by Dziedzicki. 
Before ending the general account and classification of the fungus 
gnats, one word for their preservation. If, as mentioned in a former 
page, they do a certain amount of damage to mushrooms, the amount 
done is small compared with the benefits derived from their exist- 
ence. The larve of these gnats act as “scavengers”; not only do 
they do away with rotting fungi, but they cause these often injurious 
productions to putrefy and to become scarce by their destruction. I 
have seen large fungi on chestnut trees that were gradually increasing 
in number, until one of nature’s balancers came to the fore. The 
fungi, the first year of the attack of these Mycetid larve, decayed 
sooner than usual, and after that year they gradually decreased, until 
now scarcely any are to be found. This work was done, then, by 
these larve, which were abundant in most of the fungi, and from 
which I bred several species of Mycetids ; had the production of the 
fungi continued at their rate of increase the trees must certainly have 
suffered. We now pass on to the more detailed part of the subject, 
and commence with the sub-family Scarine, 
Chironomus, F. 
Histea, F. 
Molobrus, Macq. Lat. 
Tipuda, Lin. 
GENUs.—Sciara, Mg. = 
The members of this genus are small, and generally dark in 
colour, elongated and attenuated posteriorly. The antenne are 
porrect, 16-jointed, and have a few short hairs on each joint, the two 
basal joints devoid of hair. Five longitudinal nerves to the wings, the 
third forked and branching from the second about one-third from the 
base; wings longer than abdomen. Palpi curved downwards, 3 or 4- 
jointed. Proboscis large in proportion to the head ; the labium is a 
