592 



NA TURE 



[February 27, 1902 



minute. It is familiar knowledge that the intensity and the 

 polarisation of reflected and transmitted lights vary with the 

 incidence ; and it seems likely that in the Morpho the changing 

 tints of blue may arise through a varying partition of the re- 

 flected and transmitted colours. While, then, diffraction does 

 not usually affect the appearance of the wings, it is, however, 

 interesting to a student in optics to use the scales for experi- 

 ment. Let a few wings, light-coloured for preference, have the 

 scales scraped off on to a piece of glass, and let these be covered 

 with glass as in a lantern slide ; when they are placed in strong 

 sunlight, there is the appearance of so many minute sparkling 

 diamonds. 



Since I wrote before, I have felt that in humming-birds also 

 the colour is seldom due to diffraction. In one which I have 

 before me, the head is red or black, the breast is golden or olive- 

 green ; the details of the feathers have two colours, one on 

 each edge. They are sirong mixed colours, not like spectrum 

 colours of any order. In the Oould collection at South Ken- 

 sington I was, however, able to find two birds — Rliodopis 

 i'e<per and Calyple anitae — in which the pigment colours were 

 so subdued that diffraction lights were able to have some 

 influence in the mixed effect. W. B. Croi- i. 



Winchester College, February 17. 



Birds attacking Butterflies and Moths. 



I.N connection with the controversy on the above subject, I 

 am permitted to add the testimony of an old friend of mine, .Mr. 

 H. S. Wise, of Kord, Drewsteignton, South Devon, an ex- 

 tremely keen and accurate observer, with wide experience both 

 of British and Indian fauna. In letters to me dated February 9 

 and 12, 1902, he says: — "I have seen birds attack butterflies 

 both in England and in India," and gives the following notes : — 

 "On summer evenings, magpies hunt a grass field and catch 

 immense numbers of moths, beetles and, I believe, butterflies. . . 

 Last summer I .shot a magpie, one of a family that was care- 

 fully working a large grass field ; his beak was full of recently- 

 caught Swift Moths (ffepialiis hipulinus)." Later he says, " I 

 have seen the common spotted flycatcher pursue a butterfly and 

 miss it, giving up the pursuit ; this was of course on the wing." 

 Further, ''titmice eat quantities of small moths, which they 

 catch when at rest." Speaking of the large Yellow Underwing 

 {Tryphoena pronuba], Mr. Wise tells me, "several small birds 

 eat this moth, sparrows among the number ; it is a strong moth, 

 and the bird generally beats it on the ground to kill it before 

 eating it. This insect is fond of lying on the ground among 

 leaves, &c., and birds will hunt it out and catch it." Among 

 other enemies of British Lepidoptera, Mr. Wise notes that "bats 

 feed largely on the night-flying moths ; Tryphoeua iant/iiim is one 

 I have seen them catch." My friend also refers to a note by 

 G. C. Dudgeon, in the Journal of the Bombay Natural History 

 Society for .March 20, 1895, on the King Crow (Dici-uius longi- 

 laiidatiis) catching a butterfly ( Teiiiopalptis imperialis, i ), and 

 adds, " In the case of a jungle-fire in an Indian forest, birds 

 at once come and catch the numerous insects which fly up lor 

 safety, the above-mentioned King Crow being always to the 

 fore." In India also lizards are formidable enemies to Lepi- 

 doptera. .Mr. Wise says, " in Bombay there is hardly a lamp- 

 post which has not got a gecko on it ; these feed on the moths 

 which are attracted to the light." 



.Mr. H. S. Wise, I am glad to say, promises to devote especial 

 attention this summer to the question of birds attacking Lepi- 

 doptera, and to note, whenever possible, the name of the bird 

 and the victim. If naturalists would more generally devote time 

 to such work, we should soon accumulate sufficient direct 

 evidence of the severity of the struggle for existence to place the 

 matter beyond the possibility of dispute. 



I regret to find I that in my previous letter (p. 299) I 

 unintentionally added a word to Mr. Lafter's phrase, which 

 should read " relinquished its hold in consequence of a luckily- 

 aimed stick" — not ''only relinquished," i&c. The difference 

 is not, however, essential, as the stick is stated to have been a 

 cause of the bird's action. Lilian J. Vei.ev. 



20 Bradmore Road, Oxford, February 15. 



One morning in 1901 (actual date not recorded) I found a 

 Humming-bird Hawk (Afacroglossa stellatarum) on a window in 

 my house. I opened the window and tossed it out, thinking it 

 would fly away, but it fell to the ground, where it remained 

 quivering its wings within six feet ofme. 



NO. 1687, VOL. 65] 



A House Sparrow flew down from a deodar, and with four 

 dexterous pecks separated the wings from the thorax : it then 

 pecked the middle of the thorax, splitting it, and one or two 

 more pecks separated the abdomen from the thorax. Taking the 

 abdomen in its beak, the sparrow flew back to the tree from 

 which it had come and, I presume, made a hearty breakfast. 



The sparrow al tacked the hawk in such a business-like way 

 that it was obviously no new proceeding on its part. 



There is always a martin's nest in my porch, and it is not un- 

 common to find wings and thorax of Agrotis, 6tc. on the seats or 

 floor. John Harti.ev Durr..\nt. 



Merton Hall, Thetford. 



The Severn Bore. 



SlNiE writing to you on February 12, I have had the oppor- 

 tunity of observing the bore of this morning, a tide which 

 corresponds with that of February 12, 1899, which was remark- 

 able. But to-day's "head" was a very poor one indeed, for 

 no reason that I can find out ; no wind and no fresh water in 

 the river of any consequence. The only measure that I 

 could make was of the wave at the shore, which at one point, 

 and one point only, rose to 2^ feet, whilst in midstream there 

 was but little visible. 



A distance of 520 yards having been measured out, and the 

 time of passage having been taken by watches, I found that the 

 speed was a fraction under 15 miles per hour. 



The period occupied by the passage of the ''head" from 

 Newnham ferry was one hour; the mileage taken from the 

 ()rdnance map is a little over ten miles; average speed is, 

 therefore, ten miles per hour. 



This average cannot be far from correct, for I measured 

 at Newnham, where the river is broad, and with wide sand- 

 banks, which spread out on either side, up to Framilode, a 

 distance of 5 '2 river-miles, and here the banks begin to approach 

 one another, and at five miles further up the stream is only 250 

 feet wide. F. W. I'revost. 



Newnham, February 24. 



Beautiful Birds. 



I.N reviewing my child's book, "Beautiful Birds,'' F. E. B., 

 writing in your columns, says, " Why should he select the ' beau- 

 tiful birds' only, and, by implication, condone the massacre of 

 birds that have not that advantage ?" The question is a misstate- 

 ment of fact, which I hope you will allow me to show, though I 

 can only do so by quoting myself. On the last page — which I 

 daresay F. E. B. did not get to — there is this : " ' Mother, promise 

 not to wear ciuy feathers except the beautiful ostrich feathers that 

 you look so love/ym ?' As soon as she has promised, then all the 

 beautiful birds in the world (and that means all the birds, for all 

 birds are beautiful) will be saved," &C. (The italics are mine). 

 This is the fina' promise and the goal to which I have been 

 leading. May I ask F. E. B. whether, if he wished to arouse 

 a child's interest and sympathies in any .subject, he would 

 choose the more or the less salient material to do it with ? 



19 Clarence Square, Cheltenham, Feb. 9. El>.\lfNl) Selous. 



I .\i)Mrr that I did not observe the phrase which Mr. Selous 

 quotes from his book. But supposing that he can quote half-a- 

 doren such, I cannot allow that my observations to which he 

 takes exception contain any injustice to him or real misstate- 

 ment of fact. I would commend to Mr. Selous Dr. Samuel 

 Johnson's sound remark concerning a quite analogous statement. 

 An orchard, observed the Doctor, would be properly described 

 as barren of fruit, even if subsequent research discovered a dozen 

 apples and pears upon two or three trees. Now Mr. Selous' 

 book is called " Beautiful Birds.' It is not called " Birds." It 

 is clear, too, what Mr. Selous means by "beautiful." His 

 plates and the greater part of his descriptions deal with the 

 Paradiseidx, Humming Bird.s, and other birds which everyone 

 calls beautiful. I do not find chapter after chapter relating to 

 partridges, quails, sparrows, and other " plain " birds. 



F. E. B. 



King Og"s Bed. 



A Hedraist once told me that bethought thatOg's iron bed, 

 mentioned in Deuteronomy iii. , 11, was a sarcophagus of 

 basalt. The Hebrew word is " barzel," which is evidently the 

 same as the Ethiopic "basal," iron, which Stormonth's 

 dictionary gives as the derivation of "basalt." O, Fisher. 



Harlton, Cambridge, February 20. 



