494 MOTIONS OF INSECTS. 



Dipterous insects, wliicli in general have these organs, and some three 

 on each foot', are not exclusively gifted with themf 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, 

 particuhuly those of B. fascicularis . A Brazilian beetle in my cabinet, 

 belonging to the family of the Chrida, but not arranging well under any 

 of Latreille's genera, which I have named Priocera varicgata, has curious 

 involuted suckers on its feet. The strepsipterous genera Stylops and 

 Xcnos are remarkable for the vesicles of membrane that cover the under 



taching every part of it from iheir 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 rubbing of the tarsi together, 

 as it usually does, that the object is rather for the purpose of completing the entire cleansing 

 of the tarsal brushes (for which the row of strong hairs visible under a lens on the exterior 

 margin of the wings seems well adapted), so that they may act more perfectly on the pul- 

 villi. Here, too. it should be noticed, in proof of the importance of all the pulvilli being 

 kept clean, that as the tarsi of the two middle legs cannot be applied to each other, flies are 

 constantly in the habit of rubbing one of these tarsi and its pulvillus sometimes between 

 the two fore tarsi, and at other times between the two hind ones. I ought also not to omit 

 stating, that having taken out of a spider's net one of the minute Chaicididce just caught, 

 and pulled away the threads attached to it, it spent some time in passing its hinder tarsi over 

 its wings and abdomen, and then in passing its fore tarsi through its palpi, apparently as in 

 the case of flies, to clean its pulvilli from any remains of the spider's net ; and that having 

 surrounded a minute beet'e (Meligethcs aiieus), which chanced to be on the window, with a 

 slight circle of moisture, it was unable to pass through it, and repeatedly drew its wetted 

 fore tarsi through its mouth, and rubbed the hind tarsi together ; and that precisely the same 

 results took place in the case of an Ichneumon placed in similar circumstances, only it spent 

 much more time in rubbing both its fore and hind tarsi together after being wetted, and in 

 passing the former over its antenncc and through its mouth ; and when powdered with flour, 

 It spent, like the flies before mentioned, some minutes in cleaning itself by the same processes. 



Though the above observations, hastily made on the spur of th^ occasion since beginning 

 this note, seem to prove that it is necessary the pulvilli of flies and of some other insects 

 should be kept free from moisture and dust to enable them to ascend vertical polished sur- 

 faces, 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 pro- 

 gression ; and my main reason for here giving these slight hints is the hope of directing the 

 attention of entomological and microscopical observers to a held evidently, as yet, so imper- 

 fectly explored. 



After writing the above, intended as the conclusion of this long note, I witnessed to-day 

 (July 11) IS 12) a fact which I cannot forbear adding to it. Observing a house-fly on the 

 ■window, whose motions seemed very strange, I approached it, and found that it was making 

 violent contortions, as though every leg were affected with S;. 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 eflbrt get first one and then another 

 detached, yet the moment they were placed on the glass again, they adhered as if their un- 

 der side were smeared with bird-lime. Once it succeeded in draging 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 suc- 

 ceed 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 ililliculty 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 feel with a lens, it seemed by a vigorous effort to regain its powers, and ran quite ac- 

 tively on the glass, and then flying away I lost sight of it. I am unable to give any satis- 

 factory 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 ad- 

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

 far in favor of I\Ir. iJlackwall'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 muscQlar strength of the fly was able to cope 

 with. 



• Philos. Trans. 181(7, 325. t. xviii. f. 8—11. 



