OF THE GLOWWORM (LAHPYRIS NOCTILUCA). 67 



pendently of any diminution of temperature or supply of food to the 

 larva, the interval of time between each successive change is pro- 

 gressively increased ; and this occurs in the larvae of all insects, 

 and perhaps the young of all animals. So that at last a very long 

 period may elapse between the young glowworm's penultimate 

 change of skin, and that by which its larva or simple period of 

 growth is terminated, by its assuming the quiescent state of a 

 nymph ; and if any yet earlier changes are retarded, either through 

 late development from the ovum or insufficient supply of food, or 

 through the influence of external physical causes, its growth is 

 arrested, and the animal does not complete its development as a 

 larva until the following summer. Thus the changes of the being 

 are influenced by physical causes, and subject to physical laws. 



It is only by reference to these circumstances that we are 

 enabled to understand how the glowworm occasionally passes more 

 than an entire year without undergoing its metamorphosis to the 

 perfect state, seeing that this its latter stage is always attained in 

 the month of June and July in this country. Yet the concurrent 

 observations of naturalists have shown that this is the case. 

 Bogerson noticed that it may be a year and nine months before it 

 becomes a perfect larva ; and I have certainly found this to be the 

 case in some under my own observation. As my specimens were 

 numerous, I was enabled to observe their habits during the winter 

 and their change to the perfect state ; but as I had by accident 

 lost most of the brood I had reared, and watched to their second 

 change, my observations were made on others supplied to me at 

 the end of September from their natural haunts. I preserved 

 them in an earthen vessel partly filled with mould and a turf of 

 grass, and secured at the top with gauze. An abundance of 

 Helices were supplied to them, and some of the larvae seemed 

 almost never to desist from feeding. I put with these the only 

 four remaining specimens of the brood I had reared. The whole 

 continued to gorge to repletion during the first part of October, 

 and gave out light freely when touched, or in any way compressed. 

 The temperature of the room in which they were kept was at this 

 time ranging from 50° to 55° Fahr. 



In the evening of the 18th of October, when the temperature of 

 the room was 50° Eahr., the larvae were still active and feeding ; 

 they were very healthy, and some of them were shining — one very 

 brightly. 



On the 25th of November I found them still feeding, but the 



largest were less active in their movements ; they seemed to be in 



5* 



