FARMERS' REGISTER— ON TilE GENERATION OF INSECTS. 



343 



power to quicken them into life;'and whieh, with 

 I'esjject to many of them, arc only found obvious 

 to the senses in different descriptions of animal 

 fluids.*" 



It ai)pears to us that it can be nothing more than 

 a fancj^, which is quite unsupported by evidence, 

 to say that the eggs of any species of animalcules 

 or insects float about in the atmosphere; for, inde- 

 pendent of their weiglit, (every known species 

 being greafly heavier than air,) the parent insects 

 of every species whose history has been accurate- 

 ly investigated manitcst the utmost anxiety to de- 

 posite their eggs upon or near the appropriate food 

 of the young. To connnit them to the winds 

 would be a complete dereliction of this invariable 

 kiw of insect econom3^ But admitting for a mo- 

 ment this hypothesis, that the eggs oi' insects are 

 diflused through the atmosphere, the circumstance 

 must be accompanied wiUi two conditions, — the 

 eggs must either be dropped by the parents while 

 on the wing, or be carried oft' by winds from the 

 terrestrial substances upon which they may have 

 been deposited. 



On the supposition that the eggs are dropped by 

 (lie mother insects while on the wing, we must 

 also admit (for their is no avoiding it) that they 

 continue to lioat about, unhatched, from the end of 

 the summer till the commencement of spring, at 

 which time only the broods make their appearance. 

 Yet when we consider the rains, snows, and winds, 

 to which they must be exposed for six or nine 

 months, we think the liardiest theorist would 

 scarcely maintain that a single egg could out- wea- 

 ther these vicissitudes, and continue to float in the 

 air. It may not be out of place to remark, that 

 the female aphides, which dcposite eggs in autumii, 

 have no wings. 



Again, on the supposition that the eggs are de- 

 posited on plants, trees, or other objects, it is 

 still more unlikely that they could be carried into 

 the air; tor, on exclusion, they are, with very few 

 exceptions,! enveloped in an adhesive cement 

 which glues them to the spot on which they are de- 

 posited. When eggs are deposited singly, this 

 cement usually envelopes each with a thin coat- 

 ing, as in the instance of the admirable butterfly 

 C Vanessa jitalanta;) but when they are placed 

 in a group the cement is sometimes spread over 

 the whole, as m the instance of the white satin 

 moth (^Leucomr salicis, Stephens.) This ce- 

 ment is evidently intended by nature (who seldom 

 accommodates her plans to our theories) to pre- 

 vent the eggs from being carried from the place 

 selected by the mother insect for their deposition. 

 Those eggs, thereibre, which are placed on the 

 outside of substances, have this provision for their 

 secure attachment to the locality chosen by the 

 instinct of the mother. But, on the contrary, the 

 principle does not always hold in the case of those 

 deposited in nests and excavations, and particular- 

 ly as to those of ants and termites. The working 

 ants, indeed, carry the eggs from the top to the 

 bottom of their galleries, according as the weather 

 is lavorable or unlavorable for hatching. The la- 

 borers of the white ants (Termites^) again, attend 

 their queen with the utmost care when she is lay- 

 ing; for as she cannot then move about, they are 



*Good's Study of Medicine, v. i., p. 339, 3d edition, 

 London, 1829. 



tLatreille, Hist. Gener., xiv., p. 342. 



under the necessity of carrying^ofl' the eggs, as 

 they are laid, to the nurseries. The extraordinary 

 labor which this requires in the community may 

 be understood, when, according 1o Sm<»atliman, 

 she lays 60 eggs in a minute, which will amount 

 to 86,400 in a day, and 31,536,000 in a year. The 

 exceptions now mentioned, however, do not in 

 the least invalidate our general position. 



Another no less remarkable circumstance is 

 the great weight, or specific gravity, of the eggs 

 of insects. From numerous experiments we may 

 venture to say that those of all the sj)ecies which 

 wc have tried sink rapidly in water the moment 

 they are thrown into it, from the egg of the drinker 

 moth ( Oclonestis Potatorla, Germak,J which is 

 nearly as large as a hemp-seed, to that of the rose- 

 plant louse (^jfphis rosea,) which is so small as to 

 be barely visible to the naked eye. Some eggs of 

 the gipsey moth (^Hypogymnadispar, Stephens,) 

 indeed, floated in water, because they vveve cover- 

 ed with down. It is well known, as we shall pre- 

 sently show, that the difl'usion of many of the 

 seeds of plants is accomplished by the winged 

 down with which they are clothed; but the down 

 upon the eggs of insects does not conduce to this 

 end. Whether insects' eggs be naked or clothed 

 with dov^^n, they are invariably, as far as their his- 

 tory has been investigated, deposited close to or 

 upon substances capable of affording food to the 

 young when hatched. In making experiments 

 upon the specific gravity of eggs, it should be re- 

 membered that no infertile or unimpregnated egg 

 will sink; for having some hundreds of these laid 

 by different species of insects reared m our cabinet, 

 we found, upon trial, that they uniformly flpated, 

 while those which we knew to be impregnated as 

 unilbraily sunk. A female, for example of the 

 rose-leaf roller (Lozotcenia Jiosana, Stephens^ 

 was reared by us, in solitude, under an inverted 

 wine-glass, upon the side of which she glued a 

 patch of egCTs, of course, unimpregnated: these, 

 upon trial, all floated in water. But eggs of the^ 

 same species taken from the outside of a pane of 

 glass close to a rose-tree, all sunk in water; and it 

 is to be fairly presumed, as the parent of the latter 

 was in a state of freedom, that these were impreg- 

 nated. We found the same distinction, indeed, to 

 hold in the eggs of the drinker moth, the gypsey 

 moth, and numerous other insects.* 



Dr. Good's account of "honey-dew," which he 

 describes as "a peculiar haze or mist loaded with a^ 

 ])oisonous miasm," that stimulates "flie leaves of 

 the hop to the morbid secretion of a saccharine and 

 viscid juice" — appears to us unsupported by facts. 

 Linna3us,t on the contrarj^, who was not wedded 

 to the meteorological theory- of a miasmatous haze, 

 ascribes the honey-dew on the hop leaves to the 

 caterpillar of the ghost moth (Hepialvs humuli) 

 attacking the roots. Dr. Withering, favoring this 

 account, recommends covering the roots with 

 stones as a preventive; for the caterpillars, he 

 avers, never attack wild hops which grow in stony 

 places, because they cannot get at the roots. f It 

 appears to us, however, that there can be little 

 doubt that the sweet syrupy coating, called honey- 

 dew, found on the leaves of the hop, is nothing 



*J. R. 



tQuoted by Keith, Pliys. Bot., h. 143. 

 JBotan. Arrangement, ii., 440, 3d ed. 



