52 THE INSECT WORLD. 
the nutritive substances contained in the ground. After having 
done so, they are obliged to come out of it, in order to seek at 
a distance a place where they will find food, or perhaps only 
a suitable place to undergo their metamorphosis. It is then that 
this singular journey commences. As regards the uniting of 
these myriads of individuals into columns, M. Guérin-Méneville 
thinks that it can be explained by the necessity these insects feel 
for mutual protection against the drying effect of the atmosphere 
when they are forced to leave the ground. United into masses, 
and moistened by the glutinous matter which connects them, they 
can leave their former place of abode without danger; if each 
were by itself, they would soon perish. Here, as in other cases, 
union is strength; and the strength of these larvee lies in this 
protecting moisture. However it may be explained, the migra- 
tions of these troops of insects are among the most astonishing 
phenomena of nature. 
BRACHYCERA. 
The Brachycera, from Boayts, “ short,’ and épas, “a horn,”— 
these Diptera having short antennse,—are divided into four groups. 
In this subdivision the sucker is composed of six bristles. Amongst 
other families it includes that of the Tabanide; the insects be- 
longing to which family are of remarkable strength, and possessed 
of daring and courage in the highest degree. Their wings are 
provided with powerful muscles, their feet are very strong, and 
their trunk is provided with six flat, sharp lancets. Distributed 
over the entire world, their instinct is everywhere the same: it 
is the desire for blood, at least in the females, for the males are 
not so warlike. They do no harm, but live on the juices of 
flowers. They are chiefly found in woods and pastures, and, 
during the hottest part of the day in summer, may be seen flying 
about, seeking for their prey. 
M. de Saint-Fargeau has described the manner in which the 
males fly. They may be seen flying hither and thither in the 
glades of woods, remaining for some time suspended in the air, 
then darting quickly and suddenly away a yard or two, again 
