708 Retrospective Criticism. 



portion to its consumption : that " bursting buds, lengthening shoots, expand- 

 ing leaves, swelling fruit," or swelling galls, equally attract currents of sap, 

 and in the last instance, even into a foreign channel ; proving what Du Petit 

 Thouars, and other botanists, have long ago advanced as their opinion ; viz. 

 that the growth of a tree is not caused by the motion of the sap, but the 

 movement of the latter is caused by the distension of the various members. — 

 J. Main, Chelsea, Sept. 26. 



The Excrescences iqoon the Oaks mentioned by your Correspondent in p. 498. 

 were very numerous here (North Riding of Yorkshire) this summer. Those 

 which I observed, however, could not aptly be compared to strings of the 

 Champagne currant ; one, two, or three globular processes, considerably larger 

 than the berry of a ciu'rant, being attached, at wide intervals, to a slender 

 stalk 1 in. or 2 in. long. The globules were soft and spongy in texture, 

 something like the cellular substance of an aloe leaf, but probably destitute of 

 organisation; and every one which I examined had a little round hole in its 

 side, communicating with a larger chamber in its interior, evidently once the 

 habitation of an insect, which, after changing from the egg to the larva state, 

 had eaten its way into the light. The strings appeared to me to be the stalks 

 of the male flowers of the oak (which had remained attached to the branches 

 after the flowers themselves had fallen off) ; and the " berry-like excrescences " 

 were, no doubt, caused by the punctures of some insect for the purpose of 

 depositing its eggs, in the same way as the excrescence called the " oak-apple " 

 is produced. I observed many similar galls upon the midribs of the leaves; 

 and some that I lately examined contained, in their interior cavities, ^each a 

 diminutive, roundish, brown-coloured shell, the remains of an insect egg ; and 

 in one, which had not the usual little hole in its side, I found a small dead grub. 

 Wasps feed upon the extravasated sap of the oak, as well as upon that of the 

 elm : hornets are unknown here. — J. B. W. Sept. 15. 1836. 



Cossus Ligniperda Fabricius, Zeuzera ce'sculi Latreille, Jiorciis parallelopi- 

 pedus Macleay, and other Species of Insect treated of in p. 463 — 471. : cor- 

 rective and additiojial hformation on. — A printer's proof of the treatise referred 

 to was submitted to J. O. Westwood, Esq., secretary to the London Ento- 

 mological Society, in the hope of obtaining of him the kind service of his 

 correcting any errors that he might find included in it. The proof was not 

 received back from him in time to infuse into the treatise the corrections and 

 additions that he had made, and the chief of them are now presented : — 



In p. 463. line 16,, for " Stephens,'' read " Macleay; " in line 33., for "in 

 some species," read "in a very few species; " in line 45., for "the species 

 whose," read "the species Hippobosca equina, whose." 



P. 464., 465. Cossus Ligniperda. Li relation to the etymology of the word 

 Cossus, Mr. Westwood has stated that Linnaeus called the insect Phalae^na 

 (^ombyx) Cossus, considering that its larva was the animal eaten by the 

 Romans, under the name of cossus ; but which others have supposed to be 

 the larva of the stag beetle. — " Classification." Cossus is of the family 

 Hepialidse of Stephens. — " Egg." Each female has but one course of laying 

 in its life. 



P. 465, Mr. Westwood has been so kind as to supply, at my request, a 

 drawing to represent {fig. 110.) the jaws, or mandibles, of the larva, with 

 which it cuts its way through the wood: a is a man- j^o 



dible ; b is marked as the labrum, or upper lip ; c as the 

 clypeus. The mandibles, in a living larva that I have 



seen since the matter in p. 465. was prepared, were [ ^*SM-B^ - j . e 

 formidable-looking instruments, and seemed as if each 

 were a sort of chisel with a toothed edge : in the part 

 receding from the edge it was obviously stout, and, so, 

 looking strong. 



P. 466. in lines 23. and 24., for " the hinder edge of its abdominal segments 

 bearing prickles directed backwards," read " the abdominal segments each 

 bearing two rows of prickles directed backwards." 



The following note is by Mr. Westwood, and relates to p. 465. and 466. : — 



