H4 EVENINGS AT THE MICROSCOPE. 



hints is the hope of directing the attention of entomologi- 

 cal and microscopical observers to a field evidently, as yet, 

 so imperfectly explored. 



''After writing the above, intended as a conclusion of 

 this note, I witnessed to-day (July 11, 1842) a fact which 

 I cannot forbear adding to it. Observing a house-fly on 

 the window, whose motions seemed very strange, I ap- 

 proached it, and found that it was making violent contor- 

 tions, as though every leg were affected with St. Vitus's 

 dance, in order to pull its pulvilli from the surface of the 

 glass, to which they adhered so strongly that though it 

 could drag them a little way, or sometimes by a violent 

 effort get first one and then another detached, yet the 

 moment they were placed on the glass again they adhered 

 as if their under side were smeared with bird-lime. Once 

 it succeeded in dragging off its two fore-legs, when it 

 immediately began to rub the pulvilli against the tarsal 

 brushes ; but on replacing them on the glass they adhered 

 as closely as before, and it was only by efforts almost con- 

 vulsive, and which seemed to threaten to pull off its limbs 

 from its body, that it could succeed in moving a quarter 

 of an inch at a time. After watching it with much interest 

 for five minutes, it at last by its continued exertions got its 

 feet released and flew away, and alighted on a curtain, on 

 which it walked quite briskly, but soon again flew back to 

 the window, where it had precisely the same difficulty in 

 pulling its pulvilli from the glass as before ; but after 

 observing it some time, and at last trying to catch it, that 

 I might examine its feet with a lens, it seemed by a vigor- 

 ous effort to regain its powers, and ran quite actively on 

 the glass, and then flying away I lost sight of it. I am 

 unable to give any satisfactory solution of this singular 

 fact. The season, and the fly's final activity, preclude 

 the idea of its arising from cold or debility, to which 

 Mr. White attributes the dragging of flies' legs at the close 

 of autumn. The pulvilli certainly had much more the 



