114 LETTERS ON ENTOMOLOGY. 
which Reaumur has illustrated with engravings, 
but I fear I cannot make it clearer. The beau- 
tiful feathery antennae of many kinds are visible 
even to the naked eye. The tipulidos, which 
strongly resemble the gnat, are, however, essen- 
tially different in not having any trunk or offen- 
sive weapon ; they have only a mouth without 
even any teeth. They are a very numerous tribe, 
and are probably generally mistaken for gnats. 
They are for the greatest part born under ground, 
while the maggot of the gnat is always aquatic. 
You must often observe, even in winter, clouds 
of little flies at different times of the day, which 
are constantly rising and falling in a straight 
line; and these are commonly of this species, 
and quite harmless. The largest tipula appears 
to be mounted on stilts, having legs of a most 
disproportionate length, which, however, are 
well adapted for walking in grass. 
The saw-flies are four- winged, and have two 
saws indented like ours, but much more curiously ; 
for the teeth themselves are indented again, and 
the fly in using them makes a double action, by 
drawing one back while she pushes the other 
forward. The use of them is to make a hole in 
the branches of different trees for the reception 
of the eggs. 
