Nov. 16, 1883.] 



♦ KNOWLEDGE ♦ 



297 



}P " AN ILLU.STRATED 



MAGAZINE OfSC;IENCE 



IpvPUINirVfORJED -EXACTIJ^DESCRIBED, 



LONDON: FRIDAY, NOV. 16, 1883. 



Contents op No. 107- 



A Naturalist's Year. By Grant I Sea Anemones. VIII, — The Dfiblia. 



Alien 207 1 By Thomas Kimber. (Ilhis) ... 'ivi 



titrange Coineidencea. By R. A. Reviews : Miracles— Some Christ- 

 Proctor 208 mas Works 3i,7 



The Birth and Growth of Myth, Correspondence : A Moonlifiht 



XX, ByKdward Clodd 299 Ascent in a Balloon— Perforated 



Tricycles in 18S3, By J, Browning ^'JO Stones in India— Ordnance Map 



The Sun's Distance. By Prof. | Measurements— Silent Lightning 



R, S. Ball, LL.D 301 —Luminosity of Plants and 



Ou Lunar Delineation. By the Animals— Discovery of America 



Rev, T. W. Webb 302 —Three Times Greater Than, &c. 308 



Pretty Proofs of the Earth's Rotun- Our Whist Column 311 



dity. By K, A, Procter. (Illus.) 303 I Our Chess Column 311 



A NATURALIST'S YEAR. 



By Grant Allen. 

 UNDER FALSE COLOURS, 



LAST niglit's frost has wrought great havoc among the 

 few lingering belated summer insects, and combined 

 with the wind and rain of yesterday has completely 

 changed the whole aspect of native life in the country, 

 both as regards the leaves on the deciduous trees and the 

 lesser fauna of tlie thickets and hedgerows. The brimstone 

 butterflies have retired quietly into the winter quarters, 

 where they will hibernate in a drowsy torpidity till the 

 desired return of .spring ; the daddy-longlegs flies are still 

 feebly laying the eggs of their leather-jackets grubs among 

 the dying roots of the cabbages or turnips; and a few 

 stray humming-bird hawk-moths, stianded on the cold 

 season, are trying even now to hunt up a head of 

 red clover or a garden jasmine for a last carnival 

 meal of scanty honey. But the insect world as 

 a whole is dead, or at least dormant ; and here on the 

 path through the meadow I have seen already half-a-dozen 

 dying bumble-bees — drones or workers, I suppose, for the 

 fertile females retire for their long sleep into the soft moss 

 or trunks of trees — who 'have fallen victims to the first 

 really hard frost of the present season. Here is another, 

 lying right in my way, cold and stiff — hfi has only escaped 

 the hungry jaws of his hereditary foes, the harvest mice, 

 to be cut oil' in the flower of his youth by the relentless 

 lingers of fast gripping .Jack Frost. I will take him up 

 and examine him closely, to see whethtsr I can't find ma- 

 terial enough in his poor, cold corpse for a short evolu- 

 tionary article to be printed in next week's Knowledge, 



Now this is really quite too bad and positively immoral 

 on the part of my ungrateful, frost-bitten bumble-bee. I 

 had got my article half-arranged and comfortably settled in 

 my own mind already, as I carried him along gingerly 

 between finger and thumb to the stile that leads into the 

 Ilolmdale turnip-field; 1 was prepared to mourn over 

 him as an idyllic creature that lived honestly, if not 

 by the sweat of his brow, at least by tlio search 

 after honey on his own account ; and now that I \\a.\o 

 .seated myself comfortably on the stile, and begun 



to examine him carefully with my little pocket lens, 

 I find I was totally and utterly mistaken as to his very 

 identity, and the miserable deceiver has been positively 

 obtaining my sympathy under false pretences. He isn't a 

 bumble-bee at all, as it turns out, but a true two-winged 

 fly — Volacrlla bonibi/lans is his Latin name — carefully 

 tricked in a well-concerted disguise, so as to betray the 

 very bumble-bees themselves into taking him for one of 

 their own community. Well, well ! I must console myself 

 under the shock with thinking, not only that far better 

 entomologists than myself have often been deceived at first 

 sight by this treacherous Volucella, but also that the very 

 bees in person can't properly distinguish it from their own 

 legitimate hyiuenopterous sisters. 



After all, the incident really in the end turns out to be 

 a very happy one ; for there are bumble-bees everywhere 

 in plenty — like the poor, wo have them always with us — 

 but Volucella is an insect you don't come across every day, 

 and it forms, perhaps, the very finest example of that 

 curious biological phenomenon known as mimicrij to be 

 found anywhere in the British Islands. In actual fact, it 

 is nothing more than a mere fly, belonging to the same 

 great insect group — the Diptera — as the house- 

 fly, the meat-fly, the gnats, the midges, and the mos- 

 quitoes, whose chief distinguishing mark it is that in 

 them the hind wings have become reduced to a pair of 

 very small knob-like structures, shaped exactly after the 

 model of the clapper in a bell ; but in outer form and 

 colour it apiiroaches so very near to the bumble-bees (which 

 belong to the totally different group of Hymenoptera, 

 including the bees, wasps, ants, and sawflies) that it is 

 almost impossible to distinguish them from one another 

 when on the wing. You have to catch a Volucella and 

 examine it closely in your hands before you begin to 

 perceive the immense number of important structural 

 difl'erences which underlie so close and deceptive an 

 external resemblance. Volucella, in fact, is a fly which 

 has taken to entering the nests of the bumble-bees, and 

 laying its eggs there, side by side with those of the 

 foundress bee who starts the colony. As the bee-larvie 

 emerge from their eggs, the Volucella larva also simul- 

 taneously hatches out, and begins at once to feed upon the 

 helpless grubs of its unwilling hosts. This, of course, is a 

 very disadvantageous practice — from the point of view of 

 the bumble-bees at least : and they would never let 

 Volucella penetrate into their subterranean nests if they 

 could possibly detect and expel her. But, to prevent 

 detection, Volucella has acquired an outer form exactly 

 like that of the unhappy insects on whom her larva; 

 are parasitic. She is black and very hairy, about 

 the size of a worker bumble-bee ; and the colour of 

 the hair is varied on different parts of the body, so 

 as to produce a banded or variegated appearance, after 

 the very fashion of her ITymenopterous victims. Nay, 

 more, to complete the resemblance, she even buzzes exactly 

 like the bees themselves. The consequence ^is, she can 

 enter the nests of the bumble-bees quite unsuspected, and 

 there lay her eggs in peace and quietness, producing larva; 

 which will feed hereafter to their hearts' content on the 

 soft, nutritious grubs of the foundress bee. 



Now, how did such a quaint resemblance between two 

 totally unrelated and liostile creatures first arise? Mr. 

 Alfred Russell Wallace, wlio shares with ^Ir. Darwin the 

 honour of independently originating the fertile theory of 

 Natural Selection, has clearly pointed out the general 

 principle upon which we must explain all such eases of 

 natural mimicry. The resemblance must have been de- 

 veloped by slow stages through the gradual eliminating 

 action of natural selection itself ; and in this particular 



