454 Retrospective Criticism. 
E. S. (p. 148. fig. 30. a 6) tends, I regret to say, from the additional initial 
affixed to his signature, to show that there still remain some disciples of 
that school, who, although they deem it an honourable mark of distinc- 
tion to rank themselves as members of that society which bears the name, 
and which ought also to adopt the principles, of the great Linnzus, yet 
apparently consider that the labours of that great master were, unlike those 
of other men, susceptible of no further improvement ; and who consequently 
overlook not only the labours of men almost equal in rank with himself, 
but also the very principles which guided him throughout his bright career, 
and which would doubtless have induced him to adopt, if not absolutely 
to propose, those very alterations and improvements in science which his 
would-be-considered disciples refuse to countenance and employ, if they do 
not actually laugh at and deride, but which more accurate investigation 
and by far greater numbers of the objects of such investigation have proved 
to be well-founded and correct. Ineed not, in this place, attempt to show 
the differences of structure which exist between the insects composing the 
family called Criocéride, to one of the genera of which, Donacia, the 
subject of your correspondent’s observations actually belongs; and the 
family Lepttridz, in the typical or chief genus of which, Lepttra, your 
correspondent has placed the insect alluded to, doubtless because Linnzeus 
himself regarded those species with which he was acquainted as belonging 
thereto. It is sufficient for my present purpose to point out. the circum- 
stance, that this difference in structure is borne out by difference in habits, 
inasmuch as the true Lepture do not form silken cells, but undergo a naked 
transformation; whereas the Donaciz, as E. 8S. himself informs us, construct 
cells for purposes which it may not be uninteresting to enquire into, more 
especially as E. 8. has left the question, whether they are the production of 
the larva or perfect insect, in doubt, and also in consequence of the circum- 
stance described by E. 8. involving the interesting enquiry of the hyberna- 
tion of insects. 
Cases of the nature of those described by E. 8. may be fabricated either 
by the perfect insect or by the larva. If by the former, they may be con- 
sidered as constructed either for the purpose of a general habitation, or 
merely for the purpose of hybernation. But it appears to me very evident 
that it was for neither of these purposes that these cases were formed. 
Indeed, in respect to habitations formed by the perfect insect, for the pur- 
poses of a general and constant, or even an occasional, habitation, Messrs. 
Kirby and Spence (Jntroduction, vol. i. p. 473.) remark, in treating upon this 
subject, “ From the next division of the habitations of insects — those 
formed by solitary perfect insects for their own accommodation —I shall 
select for description only two, both the work of spiders, which, indeed, 
with the exception of the inartificial retreats made by the Achete, Cicin- 
délze, and perhaps a few others, are the only ones properly belonging to it.” 
With regard also to the formation of habitations by the perfect insect for 
the purpose of hybernation, the same authors (vol. ii. p. 440.) observe 
that “ it does not appear that any perfect insect has the faculty of fabri- 
cating for itself a winter abode similar to those formed of silk, &c., by some 
larve. Schmid, indeed, has mentioned finding Rhagium mordax and 
inquisitor F. in such abodes, constructed, as he thought, of the inner bark 
of trees ; but these, as Llliger has suggested, were more probably the deserted 
dwellings of lepidopterous larva, of which the beetles in question had 
taken possession.” One, of the circumstances mentioned by E. S. must 
also be considered as sufficient in itself to prove that the perfect insect was 
not the architect of the cases in question, since it cannot be supposed that 
an insect living above the surface of the water, and constantly on the wing, 
would select a spot for its abode under water. 
It only remains therefore to regard these eases as the production of the 
larvee: and here the researches of thg same interesting authors will at 
