62 Proceedings of the Royal Physical Society. 
they will at once attack and mutilate one another, and I have often seen a 
specimen of this rapacious species seize another beetle in the collecting 
bottle and tear it to pieces. 
It is more difficult to observe the habits of the larva, as it lives 
exclusively under bark, but it undoubtedly feeds upon Scolytide and 
other bark-frequenting insects, and upon their larve and pupe, as it 
constantly occurs in the runs of Scolytide. 
Ratzeburg reared many specimens in captivity, and was able to verify 
these facts; he thought the larvee might also possibly feed on the vegetable 
debris produced in making the burrows and passages they construct in 
order to chase their prey. 
Though I sought for larve after finding the imago last July, I was 
unsuccessful, but I hope during the coming summer to make an attempt 
to rear some larve in captivity, with the object of ascertaining if there is 
any structural difference in the larve of the two species, or in their life- 
history. 
tatzeburg in his VForst Insecten, vol. i, p. 35, deals with the life- 
history of formicarius, and rightly includes it under the group of useful 
forest insects; though it is difficult to find the larve, the extraordinary 
abundance in which the imago sometimes appears is a testimony to the 
important part these insects play in the maintenance of an adequate check 
upon the destructive species of the Scolytidw and other foes of our forest 
trees. 
(Issued separately, 23rd October 1913.) 
