91 



tion on a comparatively calcareous soil*." The Scarites 

 abbreviatus, KoH., occupies the loftiest peaks of nearly 

 all the Madeiran islands, and was probably once abun- 

 dant over the entire ancient continent, whatsoever its 

 limits may have been, of which the present group forms 

 but an isolated part. "There are traces of it in the 

 Canaries, from whence occasional specimens have been 

 brought, and which, from the want of local data and of 

 sufficient numbers to reason upon, have in their turn 

 been severally regarded as distract. The fact however is, 

 that the species ia question is an extremely variable one, 

 assuming diiFerences of size according to the altitude at 

 which it lives, and differences of sculpture according to 

 the circumstances of the spot on which it is isolated. 

 That such is actually the case, a careful observation of 

 the many minute changes which the insect has under- 

 gone in the various islands and altitudes of the Madeiran 

 group will, I think, prove to a demonstration. For it is 

 impossible to suppose that every rock contains its own 

 species, that is to say, has had a separate creation ex- 

 pressly for itself, — a conclusion at which we must 

 assuredly arrive, if small and even constant differences 

 are of necessity specific. Rejecting therefore this hypo- 

 thesis as utterly untenable, and as contrary to all expe- 

 rience, we are driven to acknowledge that isolation does, 

 in nearly every iastance, in the course of time, affect, 

 more or less sensibly, external insect form ; — which 

 being admitted, we have at once an intelligible principle 

 * Insecta Maderensia, p. 452. 



