GEOGRAPHICAL DISTRIBUTION OT INSECTS. 491 
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, 1 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 food, — 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- 
pkagous, and the latter saprophagous. 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 thaleropliaga in 
both tribes may be further subdivided as they take their 
a It has lately been discovered that the larva of Drilus Jlavcsccns, 
a beetle, feeds upon the common snail. (.Bulletin des Scienc. Nat. 
1824. iii.297; v. 110; vi. 221.) I have found an Acarus o\\ the same 
animal. b See above, p. 219 — . 
c We employ this term, because the more common one, herbivo- 
rous, does not properly include devours of timber, fungi, dec. 
