GEOGRAPHICAL DISTRIBUTION OF INSECTS. 4-91 



ceed the former in number : but when you reflect that 

 not only a very large proportion of Vertebrate animals, 

 and even some Mollusca a , have more than one species 

 that preys upon them, but that probably the majority of 

 insects, particularly the almost innumerable species of 

 Lepidoptera, are infested by parasites of their own class, 

 sometimes having a different one appropriated to them 

 in each of their preparatory states b , and moreover that 

 a large number of beetles and other insects devour both 

 living and dead animals, you will begin to suspect that 

 these two tribes may be more near a counterpoise than 

 at first seemed probable. In fact, out of a list of more 

 than 8000 British insects and Arachnida taken several 

 years ago, and furnished chiefly by Mr. Stephens, I found 

 that 3894? might be called carnivorous, and 3724- phyti- 

 phagous c ; so that, speaking roundly, they might be de- 

 nominated equiponderant. 



Carnivorous and phytiphagous insects may be further 

 subdivided according to the state in which they take 

 their foody whether they attack it while living, or not 

 till after it is dead. To adopt Mr. W. S. MacLeay's 

 phraseology, the former may be denominated thalero- 

 phagous, and the latter sapropkagous. The British sa- 

 prophagous carnivorous insects, compared with those 

 that are thalerophagous, are about as 1:6; while the 

 phytiphagous ones are as 1:9. The thalerophaga in 

 both tribes may be further subdivided as they take their 



a It has lately been discovered that the larva of Drilus flavescens, 

 a beetle, feeds upon the common snail. (Bulletin des Scienc. Nat. 

 1824. iii.297 ; v. 110; vi. 221.) I have found an Acarus on the same 

 animal. b See above, p. 219 . 



c We employ this term, because the more common one, herbivo- 

 rous, does not properly include devourers of timber, fungi, &c. 



