INDIRECT INJURIES CAUSED BY INSECTS. 321 



Marsham that the grub of B. splnicUda was ascertained to have existed 

 in the wood of a deal table more than twenty years.' 



Another tribe of internal wood-borers belongs to the genus Sirex of the 

 order Hymenoptera. Mr. Stephens informs me that the fir-trees in a 

 plantation of Mr. Foljambe's, in Yorkshire, were destroyed by the larva^ 

 oi Sirex gigas ; while those of another, belonging to the same gentleman, 

 in Wiltshire, met with a similar fate from the attacks of Sirex juvencus. 

 In proof of the ravages made by this last insect, Mr. Raddon exhibited to 

 the Entomological Society a portion of the wood of a fir-tree from 

 Bewdley Forest, Worcestershire, of which twenty feet of its length was so 

 perforated by its larvte as to be only fit for fire-wood ; and being placed 

 in an ont-house, five or six of the perfect insects came out every morning 

 for several weeks.^ When fir-trees thus attacked are cut down, it often 

 happens that the larvae of the species of Sirex inhabiting them have not 

 attained their full growth at the time the wood has been employed as the 

 joists or phmks for floors, out of which the perfect insects, even years after, 

 emerge, to the no small surprise, and even alarm, of the inmates. An in- 

 stance of this, where several specimens of S, gigas were seen to come out 

 of the floor of a nursery in a gentleman's house, to the great discomfiture 

 both of nurse and children, is related by Mr. Marsham, on the authority 

 of Sir Joseph Banks ^; and a simihir circumstance, stated by Mr. Ingpen, 

 occurred in tlie house of a gentleman at Henlow, Bedfordshire, from the 

 joists of the floors of which whole swarms, literally " thousands," of Sirex 

 duplex Shuckard"*, emerged from innumerable holes, large enough to admit 

 a small pencil-case, causing great terror to the occupants. As the house 

 had been built about three years (the joists of British timber), there 

 could be no doubt of the larvae having been more than that time in arriv- 

 ing at their perfect state.^ Amongst the most formiilable wood-borers 

 with us is the larva of the great goat-moth (Cossiis lignipcrda*^), which 

 attacks willows, poplars, and occasionally even elms and oaks ; and from 

 its large size, and living above two years in the larva state, the holes which 

 it makes are a great deduction from the value of the tree, even if it be not 

 entirely destroyed. The larvae of Zeuzeiri cescuU, though much smaller, 

 has similar habits, and is injurious by boring into apple, pear, and walnut 

 trees. 



The insects which attack the bark of trees mostly belong to the family 

 of Scolytida: Westwood (including the genera Scolytus, Hylesimis, Ili/liirgus, 

 7\>mict!.i, &c.) ; a numerous tribe of beetles, the larvae of which, after being 

 hatciied from the eggs deposited by the parent beetle, excavate in the sub- 

 stance of the inner bark, and partly also in the adjoining alburnum or 

 sap-wood, lateral parallel channels more or less sinuous, proceeding on each 

 side from a central one (that in which the eggs were placed), and thus 

 giving to the under side of the detached bark and exposed alburnum, that 

 pinnated labyrinthine appearance, and fancied resemblance to letters, 

 which made Linne affix to* one of these insects, to be presently alluded to, 

 the trivial name of Ti/jmgraphus. When in small numbers these larvae 



1 Linn. Trans, x. 399. 2 Trans. Ent. Soc. Land. i. proc. Ixxxv. 



3 Linn. Trans, x. 403. 



4 This species inhabits the Spruce-fir {Pinus nigra'). — Shuckard in Loudon's 

 Mag. oj Nat. Hist. 1837, p. 632. 



* Trans. Ent. Soc. Land. ii. proc. Ixxxii. : and iii. proc. ii. 

 « Curtis, Brit. Ent. t. (iO. 



