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 ihejirst 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. I. viii. c. 27. 
b The Principles of Botany and of Vegetable Physiology, §310—353. 
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. d'Hist. Nat. ii. 282. 
A Vol.. I. p. 55-. e Vol. II. p. 16fi— . 
