APPENDIX 



79 



fly (Mclita>a sp.), and mourning-cloak butterfly (Euvanessa antiopa) also steadily 

 lose weight from day to day, this loss being very considerable in two of these 

 species, viz., about 35 per cent, in the case of one and 65 per cent, in the case of 

 the other. 



(with R. G. Bell) Variations Induced in Larval, Pupal and Imaginal 

 Stages of Bombyx mori by Controlled Varying Food Supply, in Science 

 N. S. v. 18, pp 741-748, December, 1904. 



One of the races of the mulberry silkworm was made the subject of experi- 

 ments directed toward a determination of the exact quantitative relation which 

 quantity and quality of food bear to the development and variations of the 

 individual insect, and to the maintenance or transmission of these variations to 

 its progeny. 



The change in quality of food consisted of a substitution of lettuce for mul- 

 berry. The lettuce-fed worms went through their moults, spinning up, pupation 

 and issuance as adults successfully. They mated freely and laid eggs which 

 developed normally. The young larvae adopted the unusual diet very reluctantly, 

 but in later life these same larvae, "educated" to its use, ate lettuce with a relish 

 which rivaled that displayed by the normal larva with its mulberry leaf. 



The most striking variation induced by this lettuce regimen was that the 

 time consumed by the metamorphosis was double the time appointed for that 

 of the normal mulberry-fed larva being three months as compared with six 

 weeks for the latter. In the commercial world this fact would offset the advan- 

 tage of the lettuce, as a cheaper food and as one available at all seasons, by 

 demanding twice the labor that is required to rear to spinning time larvae fed 

 on mulberry. Thus it appears that the lettuce experiment can not be of economic 

 value to sericulture unless it should prove that lettuce-made silk is worth the cost 

 of double labor. 



The other variations noted among the lettuce-fed "worms" have to do with 

 the larva and cocoon. All of the lettuce-fed larvae appeared to be unusually 

 "thin skinned," the body wall being stretched and shiny. The larvae were at all 

 stages characteristically heavier than mulberry-fed larvae, each of them weighing 

 at spinning time as much as, and two of them weighing 400 mg. more than the 

 heaviest of the mulberry-fed. The weights of the cocooned pupae were some- 

 what above the average among the mulberry-fed, a fact due to the large pupa 

 rather than to the amount of silk in the cocoon, as was demonstrated by weigh- 

 ing cocoon and pupa separately, whereupon it was found that the cocoon was, 

 on the average, but one-half as heavy as that of the average among the mulberry- 

 fed, in some cases falling as low as two-fifths of the mulberry cocoon's average 

 weight, and in no case rising above three-fifths. The silk appears to be less 

 strong and elastic than that of the mulberry-made cocoon. 



In the mulberry-fed worms there exists a very definite and constant relation 

 between amount of food and size as indicated by weight, the starveling individuals 

 being consistently smaller than the well nourished, the lingering effects of this 

 dwarfing being handed down even unto the third generation, although the 

 progeny of the famine generation be fed the optimum amount of food; in case 

 the diminished nourishment is imposed upon three or even two successive 

 generations there is produced a diminutive, but still fertile, race of Lilliputian 



