374 Retrospective Criticism. 



scout the idea of the bird's sleeping in the air will impute to 

 the desperateness of its necessity. 



With the considerations on the wing-muscles of birds, which 

 the above remarks may induce, it may not be irrelevant to 

 couple those which E. S. offers (Vol. IV. p. 4*36.) on the 

 powers of flight of "Sphinx A'tropos," and other insects 

 " met with at sea," at from 20 to a 100 miles from land. 

 — J.D. 



G. W:s Notices on Butterflies, &c. (p. 198— 202.) — Sir, 

 The title prefixed to G. W.'s communication (p. 198.), 

 namely, " Notes on butterflies, and other natural objects," 

 &c, somewhat disappointed me, as but little is there said 

 about butterflies, and that little of no great interest or im- 

 portance. By " the veined white butterfly" (p. 199.) is, no 

 doubt, meant the green-veined white (Pontia napi). As there 

 is another and quite different insect, Pieris cratae v gi, which 

 has been distinguished by the English appellation of " black- 

 veined white," the simple term " veined white " may apply 

 to one as well as to the other, and so may mislead the in- 

 experienced. 



The Cuckoo 9 s singing at Night. (Vol. IV. p. 147. 466., 

 Vol. VI. p. 199.) G. W. is not quite correct in saying 

 (p. 199.) that the cuckoo sings by day only. It was after 

 sunset when I heard the bird for the first time this season ; 

 and during the first week in May I heard him singing after 

 dusk, between eight and nine in the evening. This is no 

 unusual circumstance. I recollect once hearing him before 

 daylight in the morning. [See a notice on this subject inci- 

 dentally given by Mr. Clarke, p. 291, note *.] 



\7jyg(Z7iajili])endul(Z.~\ Under the date May 25. (p. 201.), 

 your correspondent says, " Although I picked up several 

 cocoons and caterpillars of the six-spot burnetmoth (2ygse N na 

 filipendulse), I did not meet with an imago." It was not 

 likely he should, as the season for the winged insect was not 

 arrived. 



[Familiarities effected with Butterflies, fyc, by Mr. Lukis. 

 (p. 222.)] I have seen enough of the familiar habits of 

 Vanessa Atalanto to corroborate, in some degree, Mr. 

 Lukis's interesting communication on that subject, in p. 222., 

 though certainly I never witnessed such decided instances of 

 the insect's "friendly intercourse with man," as are there 

 stated. Gonepteryx rhamni will often permit itself to be 

 taken up with the thumb and fingers, while it sits with closed 

 wings on the blossom of a thistle, &c, and is busily employed 

 in extracting the juices of the flower. The purple emperor 



