INSECTS AND VEIIMES. 401 



striking its tail on the ground, and against the grass that 

 stands in its way, in a quick manner, for several times to- 

 gother. 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 sub- 

 stance. MARKWICK. 



MUSCLE. FLIES. 



In the decline of the year, when 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 

 difficulty, 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 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 fast 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 them- 

 selves, 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. 



