66 MB. NEWPOET ON THE NATUEAL HISTOET 



into consideration, those 'become the most healthy and most ma- 

 tured individuals to which food in full abundance is supplied 

 diu-ing the earlier periods of existence. Improper food, or food 

 in too restricted quantity at this period, more affects the rapidity 

 and extent of growth during the su.hsequent periods of the life of 

 this insect, and probably also of other animals, than deficiency of 

 proper nourishment at any farther advanced stage, Not only are 

 the changes of the animal retarded by this deficiency, but its full 

 development is rarely if ever attained. I may mention, in support 

 of this statement, that there was a difference in the period at which 

 the eggs of the glowworm, placed in the glass tube as I have men- 

 tioned, were deposited, of only ninety-one hours, namely from 

 three p.m. June 22ud to ten a.m. June 26th ; but there was a 

 difierence in the hatching of the larvae from these very eggs of 

 nearly eight days, or more than one hundred and ninety hours, 

 namely from the morning of August 7th to that of the 15th of 

 the same month, although during the whole period of six weeks' 

 incubation, all the circumstances under which the whole of these 

 eggs were placed were exactly the same. I have constantly noticed 

 like circumstances in the development of other insects, the T^or- 

 Jicidce, Meloe, and others, and regard the facts stated as of general 

 application in development. 



These facts may help to explain what otherwise might seem to 

 be the result of imperfect observation, viz. that the larvae of the 

 same brood of glowworms do not all undergo their changes at the 

 same time, or even attain their matiu-ity in the same year, although 

 developed from the egg in the same season. For instance, the 

 most advanced individuals of those reared in the tube, underwent 

 their ^rs^ change on the nineteenth day, and the second also in the 

 same length of time, nineteeji days ; but others had not then 

 entered on tlaeir^rs^. This was on the 15th of September. Some 

 individuals of other broods obtained from their native haunts, I 

 found had midergone this change as early as the 1st of that month. 



The very earliest periods of development of the glowworm are 

 thus of considerable length, and exceed that of the majority of 

 insects. The Sphinx larva imdergoes its first two changes, if at 

 the same season of the year and at nearly the same temperature of 

 the atmosphere, within thirteen days, those of the glo'WTvorm being 

 thirty-eight (Phil. Trans. 1837, p. 315). But in proportion as the 

 temperature of the season diminishes, so is the length of time which 

 the larva continues before changing increased, the amount of food 

 supplied, heat, and other circumstances being the same. But inde- 



