212 ON THE BLIGHT OF OAKS IN THE 
think that their spurious legs, or prolegs ( propedes), 
as they are denominated by Messrs. Kirby and Spence, 
in their ‘Introduction to Entomology,’ acted as 
suckers, and that they were held to the sides of the 
phials by atmospherical pressure. It soon occurred 
to me that the accuracy or inaccuracy of this suppo- 
sition might be ascertained by means of the air-pump. 
Under this impression I applied to Dr. Dalton, who 
was so obliging as to allow me the use of his instru- 
ment, and to lend me his assistance in conducting the 
experiment. The result, however, proved the reverse 
of what I had anticipated ; for, notwithstanding the 
pressure was very greatly reduced, the caterpillars 
were still capable of ascending the phial in which they 
were enclosed: it is probable, therefore, that some 
adhesive matter, which, perhaps, is not liable to leave 
a sensible stain upon glass, may be secreted in small 
quantities by the spurious legs of these larve, and: that 
they are thus, in opposition to the attraction of gravi- 
tation, enabled to climb up the vertical sides of bodies 
with smooth and even highly polished surfaces*. A 
minute examination of the structure of the false legs, 
under a powerful microscope, might possibly throw 
some light on this curious subject, which, it must be 
acknowledged, merits further investigation. 
* The near approximation of this conjecture to the truth will 
be rendered apparent when the means by which certain animals 
ascend the vertical surfaces of highly polished bodies are treated 
upon. 
