134 EVENINGS AT THS MICROSCOPE 



as the pulvilli, thus clogged with it. After slipping down 

 from the painted surface of the window-frame, which she 

 in vain attempted to climb, she seemed sensible that before 

 the pulvilli could be brushed it was requisite that the 

 brushes themselves should be clean, and full two minutes 

 were employed to make them so by stretching out her 

 trunk, and passing them repeatedly along its sides, appar- 

 ently for the sake of moistening the flour and causing its 

 grains to adhere; for after this operation, on rubbing her 

 tarsi together, which she next proceeded to do, I saw dis- 

 tinct little pellets of flour fall down. A process almost 

 exactly similar I have always seen used by bluebottle-flies 

 and common house-flies which had their tarsi clogged with 

 flour by walking over it, or by having it dusted over them ; 

 but these manoeuvres are required for an especial purpose, 

 and on ordinary occasions, as before observed, the object 

 in rubbing the tarsi together is not to clean them, but the 

 pulvilli, for which they serve as brushes. Besides rub- 

 bing the tarsi together, flies are often seen, while thus 

 employed, to pass the two fore tarsi and tibiee with sudden 

 jerks over the back of the head and eyes, and the two hind 

 tarsi and tibiae over and under the wings, and especially 

 over their outer margins, and occasionally also over the 

 back of the abdomen. That one object of these operations 

 is often to clean these parts from dust, 1 have no doubt, 

 as on powdering the flies with flour they thus employ 

 themselves, sometimes for ten minutes, in detaching every 

 part of it from their eyes, wings, and abdomen; but I am 

 also inclined to believe that, in general, when this passing 

 of the legs over the back of the head and outer margin of 

 the wings takes place in connection with the ordinary rub- 

 bing of the tarsi together, as it usually does, that the ob- 



