DISEASES OF INSECTS. 205 



this subject a , and that the learned Willdenow has de- 

 voted a distinct portion of his excellent introductory work 

 on Botany to the diseases of Plants b , you will per- 

 haps be of a different mind : indeed, some facts I shall 

 have to communicate are so remarkable and interesting, 

 that I am sure, when you have read this letter, you will 

 not think the subject one that deserves to be slighted. 



Insect diseases may, I think, be divided into two great 

 classes ; those resulting, namely, from some accidental 

 external injury or internal derangement, and those pro- 

 duced by parasitic assailants. 



I. Under the Jlrst head we may begin with wounds, 

 fractures^ mutilations^ and other extraneous causes of dis- 

 ease. To these insects are peculiarly subject; and 

 though they are not, like the Crustacea and Arachnida c 

 and some other invertebrate animals, endowed with the 

 power of reproducing a mutilated limb, yet their wounds 

 appear to heal very rapidly, and at the time they are in- 

 flicted to produce little pain d . But if those important 

 members, their antenna, are mutilated, insects seem to suf- 

 fer a kind of derangement; the great organ of their com- 

 munication with each other, and in various respects with 

 the external world, being removed, all their instincts at 

 once fail them. I formerly related how the amputation 

 of these affects the queen-bee e . A similar result, as Huber 



a Hist. Animal. 1. viii. c. 27. 



b The Principles of Botany and of Vegetable Physiology,^ 310353. 



c Dr. Leach, from a communication of Sir Joseph Banks, has 

 given a very interesting history of a spider which, having lost five of 

 its legs, from a web-weaver had become a hunter ; these legs it after- 

 wards reproduced, though shorter than the others. Linn. Trans, xi. 

 393. Comp. N. Diet. (THist, Nat. ii. 282. 



d VOL. I. p. 55-. e VOL. II. p. 166. 



