SOMK onSEKVATlOXS l)N THE LAKV.E OF COSSUS T.KiNIPERDA. 89 



Some observations on the larvae of Cossus ligniperda, with special 

 reference to the Coleoptera haunting its burrows. 



By NORMAN H. JOY, F.R.C.S., F.E.8. 



( 'ossits lii/iiijierda, Fb., is such a coiumon moth in the Bi'adtiekl 

 neinhbourhood tliat I have had an exceptional opportunity of observinj^- 

 its depredations, although it is chieHy as a coleopterist that 1 have 

 examined the trees it has attacked. These trees are in nearly all cases 

 oaks, of which I know between 25 and 30. There are also two ash-trees 

 in this neighbourhood, one quite killed, and one elm. In nearly every 

 case about here the ('os.s•/^s- infected trees are found in small groups of 

 three or four close together ; even in one large wood where there are a 

 number of such trees they are arranged in four distinct groups. One 

 often finds that one of the trees in a group is more severely attacked 

 than the others, and is no doubt the original " source of infection."' It 

 is pi'obable that, as a rule, the ? moth very seldom travels far before 

 laying its eggs, generally laying them on the same tree it has been 

 bred from, or at any rate on an adjacent tree. This would account for 

 tliis grouping of infested trees. One also occasionally finds an old 

 tree very much eaten, with no others in its vicinity. These solitary 

 trees have obviously been attacked for many years by the moth, and it 

 would be interesting to know if the tree is in all cases standing alone, 

 i.e., without a tree within a few hundred yards of it, or is only 

 surrounded by young and healthy trees. In the few cases I know of, 

 one of these conditions prevails. 



I have noticed in every case that trees that have only recently 

 been attacked have already got a large number of dead branches on 

 them, and so no doubt are already on the down grade, and I have 

 never yet seen a really healthy tree showing signs of attack. I believe 

 that, as a rule, the moth lays its eggs on the tree from which it has 

 itself bred, and here the young larv* have a good chance of living 

 under the already weakened bark, but that if the eggs are laid on a 

 young and healthy tree the vitality of the bark resists the attack of the 

 very young larvte. 



If a forester wishes to clear himself of this pest the quickest plan 

 would be to cut down all the infested trees at the end of July. By 

 this time all the ? moths would have laid their eggs, and the full- 

 grown larvie would not yet have left the tree, as one usually finds 

 these wandering about in search of a place to hybernate at the middle or 

 end of August. Of course, it would be necessary to keep a look-out 

 during the next two years in case some eggs have been laid on a fresh 

 tree. Besides this " radical cure," I believe good can be done in some 

 cases by stripping off the dead and undermined bark in August and 

 September; one thus often finds the larvie in all stages just under the 

 bark, and they are destroyed. In a few trees where I have done this 

 while searching for beetles, I have found that the next year the sap no 

 longer runs from the tree, the bare place left dries up, and the living 

 bark heals perfectly round the edges. 



The coleoptera that are found at the exuding sap and under the 

 bark of r'os.s».s-infected trees may he roughly divided into four groups : 

 (1) The species that are exclusively found in such a situation or to 

 which this sap is certainly a special attraction ; (2) species usually 

 found under bark or at sap, but which are not specially partial to the 



