136 EVENINGS AT THE MICROSCOPE 



effort get first one and then another detached, yet the mo- 

 ment 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 appear- 

 ance of adhering to the glass by a viscid material than by 

 any pressure of the atmosphere, and it is so far in favor 

 of Mr. Blackwall's hypothesis, on which one might con- 

 jecture that from some cause (perhaps of disease) the hairs 

 of the pulvilli had poured out a greater quantity of this 

 viscid material than usual, and more than the muscular 

 strength of the fly was able to cope with." 1 



1 "Intr. to Entom.," 7th ed., p. 458. 



