70 ME. NEWPOET ON THE NATUEAL HISTOEY 



its head and neck to their fullest extent, as well as its anal 

 appendage. Although the creature is so courageous at other 

 times, it is now very timid and takes no food for several hours : 

 indeed it will not venture near a snail to attack it, as if conscious 

 of its present weakness. 



One specimen which changed at ten o'clock in the evening 

 became shining and active, and acquired its dark colour at the 

 expiration of twelve hours ; but it did not venture to take food for 

 several hours afterwards. 



The Nymph. 



On the morning of the 9th of June one of the larvse cast its 

 skin, and assumed the condition of a nymph. This specimen was 

 a female ; but a male specimen had already changed to the same 

 state only a few hours before. At mid-day, when the temperature 

 was 75*5° Fahr., a second female assumed the same condition ; and 

 on the evening of that day at six p.m., when the temperature was 

 77'5° Pahr., two others, one male and one female, also changed. 

 At ten p.m., the heat being still so high as 72° Eahr., I found the 

 whole of these giving out an abundance of light; the females, 

 although undisturbed, were exceedingly luminous, and the males 

 shone almost as brightly as the perfect insect in its state of greatest 

 activity. 



It was quite evident that in the quiescent state of a nymph, the 

 emission of the light was not the result of any direct influence of 

 the will or instinct of the insect ; it was simply the result of the 

 vital forces of the body, the manifestation of which seemed to be 

 greatly augmented by the very high degree of temperature of the 

 atmosphere. It was interesting also to notice that the whole of 

 the specimens, three females and two males, underwent their 

 change on the same day, in which the weather became much 

 warmer than for some days previously. The light emitted by 

 these insects was apparently in a ratio corresponding to the in- 

 crease of heat ; the rapid increase of the temperature operated 

 nearly equally upon the whole in inducing their transformation to 

 the nymph state, within a few hours of each other ; and, as we 

 shall afterwards learn, the^same external force equally accelerated 

 their development when they had assumed this condition. 



The mode in which the change to the nymph state is effected is 

 precisely that of the shifting of the skin by the larva ; but the 

 result of the change is different, in consequence of the operation of 



