128 EVENINGS AT THE MICEOSCOPE. 



hairs of the under side of the pulvilU. Of this I wit- 

 nessed an interesting instance in an Eristalis tenax, 

 which by walking on a surface dusted with flour had 

 the hairs of the whole length of the tai'si, as well as the 

 pulvilU, 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 thepulvilli could be brushed it was requi- 

 site 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, apparently for the sake of moistening 

 the flour and causing its grains to adhere ; for afte^ this 

 operation, on rubbing her tarsi together, which she 

 next proceeded to do, I saw distinct 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 walk- 

 ing 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 ob- 

 ject in rubbing the tarsi together is not to clean tkem, 

 but the pulvilli, for which they serve as brushes. Be- 

 sides rubbing the tarsi together, flies are often seen, 

 while thus employed, to pass the two fore tarsi and 

 tibise with sudden jerks over the back of the head and 

 eyes, and the two hind tarsi and tibiiB 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 those 

 parts from dust, I 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 



