OF THE LUMINOUSNESS OP INSECTS. 497 



The observations that have been made under a variety of circumstances 

 also tolerably harmonise with the conditions under which phosphorus 

 is luminous, in so far as its light disappears in irrespirable gases, 

 increases by warmth, but is destroyed, also like phosphorus, by cold, 

 immersion in oil, alcohol, acids, saturated solutions of salts and alkalis, 

 as also in vacuo. 



If, therefore, phosphorus appears to be the substance which produces 

 the light in insects, it may be asked, as phosphorus is not luminous in 

 itself, what may be the conditions under which phosphorus is luminous? 

 To this the above remarked differences of opinion especially refer. 

 As phosphorus can only become luminous by contact with oxygen, if, 

 therefore, we imagine it combined with the fatty substance, or with 

 its albumen, respiration gives it luminousness ; by means of respiration 

 oxygen is deposited in the corporeal substance, and each inspiration 

 therefore makes the beetle shine. Now, as we have before noticed, 

 respiration being strongest during flight, it necessarily follows that the 

 emission of light will also then be most powerful. In opposition to 

 this the wingless state of the female might be urged, yet her short 

 thicker body must contain more of the fatty substance, and must there- 

 fore emit a stronger light than that of the male. Next to respiration 

 the circulation of the blood appears to have considerable influence upon 

 the light, for we know that the substance emits the light only when 

 moist. As, now, the blood flows all round upon the fatty substance, 

 this may be considered as the moisture, which helps to support the 

 luminousness. Carus has also observed that upon each pulsation, and 

 consequently upon each fresh wave of blood, the light shines brighter. 

 He refers to this also the brighter shining of the female, as she con- 

 stantly dwells in dark, damp places. Thirdly, the nervous system may 

 exercise a certain influence upon the production of the light, for as it 

 is the chief agent of all the voluntary actions of the body, it will also 

 necessarily exercise an influence upon the voluntary suppression of the 

 light if the insect stops this influence by checking respiration in the 

 way in which it causes the nerve to act upon the muscle in muscular 

 motion. That it possesses this faculty of checking the respiration we 

 know, but that this cannot be long protracted lies in the very nature 

 of the thing, and thus by both causes the momentary cessation of light 

 which is frequently observed, and which we have mentioned before, 

 may be produced. Upon respiring anew the beetle would necessarily 



become again luminous. 



K K 



