MOTIONS OF INSECTS. 



263 



them ; for various others in different orders have them, and 

 some in greater numbers. As I lately observed, the foot- 

 cushions of the Buprestes are something very like them, par- 

 ticularly those of B. fascicularis. A Brazilian beetle in my 

 cabinet, belonging to the family of the Cleridce, but not 

 arranging well under any of Latreille's genera, which I have 

 named Priocera variegata, has curious involuted suckers on 

 its feet. The strepsipterous genera Stylops and Xenos are 

 remarkable for the vesicles of membrane that cover the under 

 side of their tarsi, which, though flaccid in old specimens, 

 appear to be inflated in the living animal or those that are 

 recent. 1 It is not improbable that these vesicles, which are 

 large and hairy, may act in some degree as suckers, and assist 

 it in climbing. 



ascend vertical polished surfaces, they cannot be considered as wholly settling 

 the question as to the precise way in which these pulvilli, and those of insects 

 generally, act in effecting a similar mode of progression ; and my main reason for 

 here giving these slight hints is the hope of directing the attention of entomo- 

 logical and microscopical observers to a field evidently, as yet, so imperfectly 

 explored. 



After writing the above, intended as the conclusion of this long note, I wit- 

 nessed to-day (July 11, 1842) a fact which I cannot forbear adding to it. Ob- 

 serving a house-fly on the window, whose motions seemed very strange, I ap- 

 proached it, and found that it was making violent contortions, 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 Avere 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 be- 

 fore, and it was only by efforts almost convulsive, 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 win- 

 dow, 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 vigorous 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 appearance of adhering to 

 the glass by a viscid material than by any pressure of the atmosphere, and it is 

 so far in favour of Mr. Blackwall's hypothesis, on which one might conjecture 

 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 Kirby in Linn. Trans, xi. 106. t. viii. f. 13. a. 



s 4 



