304 SILK-MOTHS. Chap. VIII. 



moths, but the disuse of their wings during so many generations has, it 

 may be suspected, likewise come into play. 



The moths of many breeds fail to glue their eggs to the surface on 

 which they are laid, 77 but this proceeds, according to Capt. Hutton, 78 " 

 merely from the glands of the ovipositor being weakened. 



As with other long-domesticated animals, the instincts of the silk-moth 

 have suffered. The caterpillars, when placed on a mulberry-tree, often 

 commit the strange mistake of devouring the base of the leaf on which they 

 are feeding, and consequently fall down ; but they are capable, according 

 to M. Eobinet, 79 of again crawling up the trunk. Even this capacity 

 sometimes fails, for M. Martins 80 placed some caterpillars on a tree, and 

 those which fell were not able to remount and perished of hunger ; they 

 were even incapable of passing from leaf to leaf. 



Some of the modifications which the silk-moth has undergone stand in 

 correlation with each other. Thus the eggs of the moths which produce 

 white cocoons and of those which produce yellow cocoons differ slightly 

 in tint. The abdominal feet also of the caterpillars which yield white 

 cocoons are always white, whilst those which give yellow cocoons are in- 

 variably yellow. 81 We have seen that the caterpillars with dark tiger-like 

 stripes produce moths which are more darkly shaded than other moths. 

 It seems well established 82 that in France the caterpillars of the races 

 which produce white silk, and certain black caterpillars, have resisted., 

 better than other races, the disease which has recently devastated the 

 silk-districts. Lastly, the races differ constitutionally, for some do not 

 succeed so well under a temperate climate as others ; and a damp soil does 

 not equally injure all the races. 83 



From these various facts we learn that j silk-moths, like the 

 higher animals, vary greatly under long-continued domestication. 

 We learn also the more important fact that variations may occur 

 at various periods of life, and be inherited at corresponding 

 periods. And finally we see that insects are amenable to the 

 great principle of Selection. 



77 Quatrefages, ' Etudes/ &c, p. 214. 80 Godron, « De l'Espece,' p. 462. 



78 ' Transact. Ent. Soc.,' ut supra, p. 81 Quatrefages, ' Etudes,' &c, pp* 

 151. 12, 209, 214. 



79 'Manuel de l'Educateur,' &c, p. 82 Eobinet, ' Manuel,' &c, p. 303. 

 26. S3 Eobinet, idem, p. 15. 



