198 DISEASES OF INSECTS. 
but when you recollect that Aristotle has a chapter on 
this subject*, and that the learned Willdenow has de- 
voted a distinct portion of his excellent introductory 
work on Botany to the diseases of Plants’,—you will 
perhaps 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 jirst head we may begin with wounds, 
Jractures, mutilations, and other extraneous causes of dis- 
ease. To these—insects are peculiarly subject; and 
though they are not, like the Crustacea and Arachnida‘ 
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*.. But if those important 
members, their antennae, are mutilated, insects seem to 
suffer a kind of derangement; the great organ of their 
communication 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 amputa- 
* Hist, Animal. |. vii. c. 27. 
» The Principles of Botany and of Vegetable Physiology, § 310—353. 
* 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. Dict. d’ Hist. Nat. ii, 282. * Vou. I. p. 55—. 
