112 



MEANS FOR ARRESTING THE PROGRESS OF 



Fig. 8. Plan of a fly -trap. 



which will prevent the entrance or exit of flies. The bottom hand-glasd 

 must rest on three pieces of bricks, fig. 8, to form 

 an opening underneath. The appearance of the trap 

 when completed is simply that of one hand-glass 

 above another, fig. 9. Frag- 

 ments of waste fruit are laid on 

 the ground, under the bottom 

 hand-glass, to attract the flies, 

 which, having once entered, 

 never descend again to get out, 



but rise into the upper glass, and buzz about under its 

 roof, till, fatigued and exhausted, they drop down, and 

 are seen lying dead on the roof of the under glass. One 

 of these traps, placed conspicuously on the ground be- 

 Fig. 9. Hand-glasses ar- fore a fruit-wall or hothouse, acts as a decoy to all 

 ranged as a fly-trap, j^j^^^jg ringed insects. {Gard. Mag. vol. ii. p. 152.) 



358. Collecting the Eggs of Insects. — The eggs of insects, after being depo- 

 sited on the bark or leaves of plants, may sometimes be collected by hand ; 

 for example, when they are laid in clusters or patches, so as to form a belt 

 round the twig, as in the lackey-moth ; or when they are covered with 

 fibrous matter, as in the JBomb yx di'spar, which lays its eggs in large circular 

 or oval spots, containing 300 or more each, on the bark of trees or hedges, 

 and covers them with a yellow wool. The eggs of the yellow-tail- moth are 

 laid on the leaves of fruit-trees, in a long narrow heap, and covered with 

 gold-coloured hair, whence the scientific name^ombyx chrysorrhoe'a, which 

 makes them very conspicuous ; but the leaves may easily be collected, 

 and the eggs destroyed. The satin-moth, ^ombyx salicis, which, in its 

 larva state, feeds on the leaves of willows and poplars, often stripping entire 

 trees, when it becomes a perfect insect, lays its eggs in July, in small spots 

 like mother-of-pearl, on the bark of the tree ; and as they are conspicuous, 

 they may easily be scraped off. Practical men in general are too apt 

 to undervalue the effects of hand-picking, whether of the eggs or larvae of 

 insects ; not reflecting that every insect destroyed by this means, is not only 

 an immediate riddance of an evil, but prevents the generation of a great 

 number of other evils of the same kind. Circumstances have forced this on 

 the attention of the French cultivator, and the following facts will place the 

 advantage of hand-picking in a strong light. In 1837, M. V. Audouin, 

 already mentioned, was charged by a commission of the Academie des 

 Sciences, to investigate the habits of a small moth, whose larva is found to 

 be exceedingly injurious in vineyards in France. During the month of 

 August, women and children were employed during four days in collecting 

 the patches of eggs upon the leaves, during which period 186,900 patches 

 were collected, which was equal to the destruction of 11,214,000 eggs. In 

 twelve days from twenty to thirty workers destroyed 482,000 eggs, which 

 would have been hatched in the course of twelve or fifteen days. The 

 number of perfect insects destroyed in a previous experiment, by an expensive 

 process, was only 30,000. (Gard. Mag. vol. xiii. p. 486.) Many insects, how- 

 ever, deposit their eggs singly or in very small quantities, or in concealed places; 

 and the eggs being in these cases very small, cannot be removed by art. 



359. Freventing Eggs from being hatched. — Eggs, after being deposited, may 



