HARDWICKE'S SCIENCE-GOSSIP 



1S9 



■endowed every hen cuckoo with the power of laying 

 eugs similar in colour to those of the species n 

 whose nest she lays, in order that they may not he 

 detected by the foster-parents." This is the first 

 time I ever saw it stated that the cuckoo (or any 

 •other bird) possessed a power by which it could 

 regulate the colour of its eggs ; and all the cases I 

 have had under my notice certainly do not bear it 

 out. In the first place, I do not give the birds 

 upon whom the deception is practised credit for 

 such perception as this power would imply they 

 must have to make it needful. In the second 

 place, all the eggs which I have seen have been of 

 the same colour, with very little variation. And 

 again, they are of such a colour as would seem least 

 striking against any of those which they have been 

 found in contact with. And, thirdly, the Cuckoo 

 generally, after laying her egg, turns out those pre- 

 viously in the nest, which I cannot harmonize with 

 the marvellous power which Mr. Taylor credits it 

 with. For 1 should certainly think it runs much 

 greater risk of detection by leaving only a single egg 

 in place of the three or four, than by laying an 

 additional egg, the colour of which might differ a 

 little from those of the rightful occupant of the 

 nest. One peculiarity of the Cuckoo's egg is its 

 smallness, it being only about one-fourth the size 

 one would expect from the size of the bird. This, 

 Mr. Selby suggests, may be accounted for by the 

 fact that if it were larger it would require to be laid 

 in a larger nest, the occupants of which might be 

 able successfully to resist the encroachment. But 

 in this case the Cuckoo need possess no special 

 faculties to account satisfactorily for the circum- 

 stance. Among the birds whose nests it generally 

 usurps are the following :— The hedge-sparrow, the 

 robin, the titlark, the wagtail, the redstart, the 

 whitethroat, the willow-warbler, the rock- lark, the 

 skylark, the reed-warbler, the reed-bunting, the 

 sedge- warbler, the willow-wren, the yellow-bunting, 

 the blackbird, the wren, the thrush, the whinchat, 

 the greenfinch, the grasshopper-warbler, the chaf- 

 finch, and the red-backed shrike. The eggs of 

 many of the birds here mentioned vary much more 

 than those of the Cuckoo in my experience, and if 

 I give these birds credit for such perception of 

 colour as would make this special gift of the Cuckoo 

 (necessary, I should imagine them sometimes getting 

 into greater trouble in the recognition of their own 

 esgs when they vary, as they do in the case of the 

 robins, from a dark shade to pure white, than they 

 would with those of the Cuckoo. My conclusion is, 

 therefore, that the colour of the eggs does not vary, 

 and certainly cannot be varied at the will of the 

 bird ; and that the only peculiarity noticeable in the 

 Cuckoo beyond its parasitic habit, is that it should 

 lay in the nests of birds much smaller than itself, 

 aud that its eggs should be only one-fourth their 

 proportionate size, apparently to suit the size of the 

 eggs of those nests. If any of your readers can 

 ■confirm Mr. Taylor's opinion, 1 should be glad of 

 their experience, and hold myself open to any cor- 

 rection capable of proof; but if his statement is 

 •erroneous, as I hold it to be, then I think it should not 

 be allowed to remain, to convey a wrong impression 

 in a book otherwise calculated to be so instructive 

 •to all students of science.—/. L. Cvpeman. 



The Cuckoo's Eggs.— All, or almost all, the mis- 

 takes about the Cuckoo hatching her own eggs and 

 rearing her own young have arisen from confounding 

 the nest of other birds for that ot the Cuckoo. The 

 latter never lays more than one egg in the same 

 nest, and that is always in the nest of another bird : 



it never makes a nest. The young of the Nightjar 

 have often been mistaken for the young of the 

 Cuckoo, the latter being very unlike the full-grown 

 bird. In "The Architecture of Birds " (Library of 

 Entertaining Knowledge), there is much upon this 

 point. To it I beg to refer your correspondent 

 J. G. Henderson.—/. S. Wesley. 



Water-rat.— The Water-rat, or more correctly 

 Water-vole, for it is not of the same genus as the 

 common brown rat, is entirely a vegetable-feeder. 

 Professor Bell's words (see his book) are — "Food, 

 which we have every reason to believe consists 

 exclusively of vegetable substances." — /. S. Wesley. 



Boat-flies. — I have kept many specimens of 

 Notonecta, and have always found that the sound 

 noticed by Tom Workman was produced by the 

 determined attempts of some one individual to 

 propel himself through the glass sides of the aqua- 

 rium. If the latter happens to be a bell-glass, or 

 glass jar, it can be heard several feet off. As T. W. 

 mentions having several in his aquarium, it is pos- 

 sible that his attention has been fixed on the wrong 

 individual. — B. B. Woodward. 



Management of Silkworms.— In Science- 

 Gossip for May, "Inquirer " begs for information on 

 the treatment of silkworms. In our climate it is gene- 

 rally better to retard their development by keeping 

 the eggs in a cool dry place, because if the hatching 

 is hastened, their natural food, the mulberry, is not 

 in leaf. They can be fed upon lettuce, cherry, or 

 black-currant leaves if necessary, but the former 

 fade quickly, and therefore become unwholesome. 

 It is important to remove all dead and decaying 

 matter as quickly as possible, cleanliness being of 

 the greatest consequence. It is said the "worm 

 mother " abroad puts on clean clothes every time 

 she enters the room. The worms may be kept in 

 paper trays, and supplied with fresh leaves at least 

 twice a day, — the oftener the better. Gently remove 

 them from the old remains, and put them on the 

 fresh. The difficult operation of changing the skin 

 is performed four times, when they require special 

 care, and sometimes a little assistance, to get rid of 

 the old skin, or they sometimes die in the struggle. 

 When they begin to spin, put them in conical paper 

 cases, pinned against the wall or some support. The 

 silk may be wound off by a little hand-machine, the 

 cocoon being put in a little warm gum-and-water to 

 prevent the thread breaking: winding should be done 

 before the moth eats through the cocoon, but not 

 until the chrysalis is fully matured, which will 

 usually be in two or three weeks' time, and may be 

 ascertained by gently shakiug the cocoon, and 

 hearing it rattle inside. It is better to put the 

 chrysalis in bran, and then leave the moths in open 

 boxes to deposit their eggs for next year. _ When 

 fresh mulberry-leaves cannot be gathered daily, they 

 can be kept laid singly in layers, folded in a damp 

 cloth, and put in a damp cellar or cool place. The 

 deeply indented mulberry-leaves are best ; many 

 other serrated leaves are also considered wholesome. 

 Sericulture is of growing importance, not only 

 because some consider it might afford a suitable and 

 remunerative occupation for ladies, even in England, 

 but especially since the mysterious development of 

 the silkworm disease on the Continent has tended 

 to check the supply of a useful article, and ruin the 

 many poor people whose occupation it is to cultivate 

 it. Good silk always commands a good price. Mrs. 

 Bladen Neill, a lady from Melbourne, Australia, 

 showed some very fine cocoons from that place, 

 where she has been the means of establishing a 



