NOTES AND QUERIES. 439 



of citrus trees, and causes a great distortion of foliage (Cape of Good 

 Hope, Department of Agriculture, Reprint No. 21, 1898). — Ed.] 



" Making the best of Difficulties." — With regard to the communi- 

 cation on this subject (ante, p. 392), my own experience may be of 

 interest. I have had many larvas of Dicranura vinula at various 

 times, and have always found that they can be persuaded to manu- 

 facture their cocoons out of any material which is given to them, in 

 default of the natural supply. If one of these larvae be put in a tin, 

 with pieces of coloured paper, a very pretty result may be obtained. I 

 have in my possession cocoons composed of pink paper, another of 

 blue and white, and a third of bright yellow. I have also a very 

 singular cocoon which is made entirely of white muslin and brown 

 elastic, although this specimen was quite unintentional as far as I was 

 concerned. The larva was enclosed in a glass jam-jar, over the top of 

 which I had placed a piece of muslin, with an elastic band round it, 

 to prevent the larva from making its escape. The captive was ready 

 to spin before I was aware of the fact, and, finding nothing in the 

 bottle but leaves, endeavoured to escape by biting a hole through the 

 muslin. Even then the caterpillar found that it could not get away, 

 as the overhanging edges of the muslin did not reach near enough to 

 the ground to enable it to climb down, and apparently it did not like 

 to risk a drop. Doubtless it wandered round and round the edge of 

 the muslin many hundreds of times before it finally decided to make 

 the best of a bad job, and compose its cocoon of muslin and elastic. 

 A friend of mine had another caterpillar which made its escape, and, 

 after wandering round the room disconsolately, set to work, and com- 

 posed its cocoon out of his best table-cloth ! — H. W. Shepheard- 

 Walwyn (Dalwhinnie, Kenleyi. 



SEXUAL SELECTION. 



In his interesting paper on the " Colouring of Stercorarius crepi- 

 datus," Mr. Edmund Selous gives it as his opinion that the gradations 

 of plumage in this species are due to sexual selection. He finds no 

 evidence in favour of natural selection in the case before him, and 

 consequently he sets aside all probability of that agency. "Without 

 evidence," he writes, "such a view is a mere supposition, and there- 

 fore not worth while considering. The main facts suggest choice in a 

 certain direction." 



It is the plain statement of personally observed facts which has 

 made Mr. Selous' papers in ' The Zoologist' so valuable; but what facts 



