﻿126 [November 



OBSERVATIONS ON THE CECONOMY OF THE BRITISH SPECIES 

 OP SCOLYTUS. 



BY T. ALGEENON CHAPMAN, M.D. 



1. Scolytus Eatzebtjbgii, Janson. It is somewhat unfortunate 

 that I should at the commencement of my observations be compelled 

 (after the manner of a certain chapter " On the Snakes of Iceland ") 

 to omit any remarks upon the very first species : Coleopterists, how- 

 ever, are well away that S. Batzeburgii has hitherto occurred with us 

 only at Eannoch, in birch trees ; and further particulars of it will, of 

 course, be found in the " Entomologists' Annual " for 1856, p. 86, in 

 which Mr. E. W. Janson introduced the species. All our remaining 

 Scolyti I have found in this district. 



2. Scolyttjs destettctob, 01. This, the next largest in size to 

 8. Batzeburgii, and the commonest of our species, may be found early 

 in June making its galleries of oviposition in any elm trees felled 

 during the previous winter, and usually in such numbers as to ensure 

 the destruction of the bark. I do not recollect to have seen it in 

 timber smaller than 8-in. in diameter. The female makes her way 

 along the bottom of some crack in the bark, often by widening it for 

 some distance, before commencing to burrow, so that the real opening 

 of the gallery is some distance from where the little heap of out-turned 

 frass lies which marks its orifice. 



The male is present for only a brief interval, viz., after the burrow 

 is well commenced, but before any eggs are laid, and I once found a pair 

 in cop. at this period. The burrow is usually about three inches long 

 (very rarely five inches), almost always close to the wood, and slightly 

 encroaching on it. Its construction occupies about three weeks. The 

 eggs are laid along either side close to the bark, the cavities in which 

 they lie being somewhat irregular, not nicely fitting the egg as with 

 Hylesinus. The eggs in a burrow number about 100, but I have met 

 with more than 160 in one. They are covered by a rather thick con- 

 tinuous layer of frass, which also lines the floor of the burrow, and 

 extends partially into the roof. 



The young larvae, starting at right angles to the parent gallery, 

 which is parallel with the axis of the tree, form a very regular " typo- 

 graph," at least in those somewhat rare instances, in which contiguous 

 broods do not interfere with each other. Most of the larva? are full 

 fed towards the latter part of July, and I daresay that, in favourable 

 seasons, there are sometimes two broods in a year. A certain propor- 



