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possible source of error. The influence they hare had in the formation of opinion since 
the date of their publication is the best test possible of the esteem in which they are 
held. And, in addition, the merit may fairly be claimed for them, of having stimulated 
other inquirers to a closer examination of the questions under consideration, 
E. Newman (1841)* speaks, from independent observations, of the "almost infinite 
number of minute hairs" composing "the soft cushions vt pulvilli, on the under surface 
of the joints of the tarsus," in insects generally, which, at their ends are slightly dilated, 
and constantly exude an adhesive gummy matter. By means of these gummy pule 111% 
■ insects possessing them are enabled to walk freely on smooth surfaces, even with their 
backs downwards, against the power of gravity." 
"Until lately discovered by Mr. Lister," it is added, " the true cause " by which they are 
enabled to do this "was unknown." 
Kirby and Spence do not appear to have used the compound microscope in their 
investigations into the minute structures of insects. In the earlier editions of their sreat 
° • 
work they seem to have been guided in the formation of their opinions by the weight 
they attached to Home's authority, and subsequently by Mr. Black wall's latest published 
observations. Mr. Kirby makes some valuable observations on the action of the parts 
composing the Fly's feet, as deduced from the habits of the insects, both when in what 
we may term the natural condition of the foot, and when it is defiled by the insect's 
attempting to walk on a surface slightly moistened by the breath, or coated with flour, 
or when the same material was powdered over them. 
It is added " that these observations on the way in which flies are able to support 
themselves against gravity 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 entomological and microscopical observers to a field, evidently 
as yet so imperfectly explored." 
Under date "July 11th, 1842," Kirby adds an observation of considerable interest. 
Shortly after writing the remarks above quoted, he observed a " fly on the window, 
whose motions seemed very strange. I approached it," he says, " and found that it was 
making violent contortions, as though every leg was 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 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 pulviUi against the tarsal 
brushes ; but on replacing them on the glass, they adhered as closely as before, 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 
matching it with much interest for five minutes, it at last by continued exertions got its 
feet released and flew away, and alighted on a curtain, on which it walked quite briskly, 
* 
Entom. Mag. vol. i. p. 447. Grammar of Entomology, a Familiar Introduction to the History of Insects 
