160 ON THE BLIGHT 



to try the experiment with the larvae of other 

 insects. Capturing, indiscriminately, such as 

 came in my way, I soon collected a considerable 

 number ; and, on introducing them into the 

 phials, found that several of them made their 

 way up the glass without any apparent difficulty, 

 while others were totally incapable of doing so. 

 These ascents, in many instances, were effected 

 by spinning lines, which were made to answer 

 the purpose of a ladder, as noticed above ; in 

 some, by the assistance of a slimy or glutinous 

 secretion which left a sensible trace on the glass ; 

 and in others, by a method which I cannot satis- 

 factorily explain; the caterpillars, in this case, 

 neither spinning lines, nor leaving any percepti- 

 ble trace behind them. At first, I was disposed 

 to think, that their spurious legs, or prolegs, 

 (propedes,) as they are denominated by Messrs. 

 Kirby and Spence, in their Introduction to Ento- 

 mology, acted as suckers; and that they were 

 held to the sides of the phials by atmospherical 

 pressure. It soon occurred to me, that the accu- 

 racy or inaccuracy of this supposition might be 

 ascertained by means of the air-pump. Under 

 this impression, I applied to Mr. Dalton, who 

 was so obliging as to allow me the use of his 

 instrument, and to lend me his assistance in con- 

 ducting the experiment. The result, however, 

 proved the reverse of what I had anticipated ; 



