294 OBSERVATIONS ON INSECTS AND VERMES. 
when it abounds greatly, is very prejudicial to the grains of wheat. 
This operation I have frequently seen it perform with wonder and 
delight. — Markwick. 
BOMBYLIUS MEDIUS. 
The Bomhylius medius is much about in March and the beginning of 
April, and soon seems to retire. It is an hairy insect, like a humble- 
bee, but with only two wings, and a long straight beak, with which it 
sucks the early flowers. The female seems to lay its eggs as it poises 
on its wings, by striking its tail on the ground, and against the grass 
that stands in its way, in a quick manner, for several times together. 
• — White. 
I have often seen this insect fly with great velocity, stop on a sudden, 
hang in the air in a stationary position for some time, and then fly off 
again ; but do not recollect having ever seen it strike its tail against 
the ground, or any other substance. — Markwick. 
MUSC^.— FLIES. 
In the decline of the year, when the mornings and evenings become 
chilly, many species of flies (Muscce) retire into houses, and swarm in 
the windows. 
At first they are very brisk and alert ; but as they grow more torpid, 
one cannot help observing that they move with dilflculty, and are scarce 
able to lift their legs, which seem as if glued to the glass ; and by 
degrees many do actually stick on till they die in the place. 
It has been observed that divers flies, besides their sharp hooked 
nails, have also skinny palms, or flaps to their feet, whereby they are 
enabled to stick on the glass and other smooth bodies, and to walk on 
ceilings with their backs downward, by means of the pressure of the 
atmosphere on those flaps ; the weight of which they easily overcome 
in warm weather, when they are brisk and alert. But in the decline of 
the year, this resistance becomes too mighty for their diminished 
strength ; and we see flies labouring along, and lugging their feet in 
windows as if they stuck to the glass, and it is with the utmost difficulty 
they can draw one foot after another, and disengage their hollow caps 
from the slippery surface. 
Upon the same principle that flies stick and support themselves, do 
boys, by way of play, carry heavy weights by only a piece of wet 
leather at the end of a string clapped close on the surface of a stone. — 
White. 
TIPULJS, OE EMPEDES. 
May. Millions of empedes, or tipulce, come forth at the close of day, 
and swarm to such a degree as to fill the air. At this juncture they 
sporb and copulate ; as it grows more dark they retire. All day they 
hide in the hedges. As they rise in a cloud they appear like smoke. 
