OF THE GLOWWORM (LAMPYRIS NOCTILUOa). 65 



so steadily until disturbed or again exposed to light, when they 

 ceased to shine, becoming luminous again after a short interval, 

 when the light was again removed. 



Another circumstance also which influences their shining is 

 deficiency of food. It is only when well-fed that they give out 

 light more brightly ; for if deprived of food, the light is then very 

 feeble. 



All these circumstances tend to show that the light is greatly 

 influenced by physical causes, and that those physical causes which 

 operate generally on the body, or health, or vital force of the 

 animal itself, as food, motion, heat, are precisely those which 

 affect the production of light. 



The Growth and Hybernation of the Larva. 



It constantly happens with insects as with other animals, that 

 when many individuals, constituting one brood, are hatched at 

 very nearly or exactly the same time, some of them grow more 

 rapidly and arrive at their completion much earlier than others. 

 This is precisely the case with the larvae of the glowworm. Owing 

 to this circumstance, some individuals undergo their changes more 

 rapidly, and attain to their imago state sooner than others, but 

 having reached that stage and performed the great intent of their 

 being, their life is rarely if ever prolonged beyond that of their 

 fellows in a similar state of existence. 



This difference in the rapidity of the growth appears to depend 

 on physical causes, as for instance the more complete development 

 of the constituents, and the subsequent more complete impreg- 

 nation of the ova from which these precocious growths are pro- 

 duced ; the greater amount of nourishment which the young have 

 taken during corresponding periods of time ; and generally the 

 circumstances in which the whole brood have been placed in 

 regard to light, heat, air, locality, and quality of food. I have 

 usually observed that the larger beings came first from the egg, 

 and appeared more robust and healthy than those subsequently 

 produced ; further, that a difference of but a very few hours in the 

 earlier hatching of these individuals is followed by a much greater 

 difference than can be accounted for merely by the length of time 

 between the birth and the first and subsequent changes which the 

 several individuals undergo. 



Another circumstance of very great importance, since it is 

 applicable to all beings, is, that the facts first noticed being taken 



LINN. PROC. — ZOOLOGY. 5 



