292 THE ZOOLOGIST. 



relation to the temperature, but a little consideration showed 

 that the white wings of the Pierids might act as reflectors of 

 heat, glancing off the sun's rays on to the black body of the 

 insect, which would thus absorb a greater quantity of heat. I 

 have since tried many experiments in order to test this hypothesis ; 

 the bulb of a sensitive thermometer is tied round with black 

 cloth, and hung up in bright sunshine. This morning a ther- 

 mometer so prepared registered a temperature which varied be- 

 tween 30° and 31° C. I then backed the thermometer with a 

 sheet of white paper folded so as to imitate the position of a 

 butterfly's wings when expanded upon a flower. In three minutes 

 the temperature had risen to 35° C, and was still rising when I 

 removed the paper ; the temperature immediately dropped. I 

 repeated the experiment, substituting the cups of variously 

 coloured flowers — such as poppies, Canterbury-bells, and so 

 forth — to take the place of the white paper, and I obtained rises 

 of temperature through two or three degrees, according to the 

 reflecting powers of the various colours ; the worst reflector 

 being a dark purple larkspur, and the best a bright red poppy, 

 which increased the temperature from 30*3° to 33'5° C. in a few 

 minutes. 



I surmise therefore that the influence of colour on the tem- 

 perature of Lepidoptera is not so simple as it is usually assumed 

 to be ; on the one hand, the wings may absorb heat directly ; 

 on the other, they may be used as reflectors. It has been urged 

 that the absorption of heat into the wings is a useless pro- 

 ceeding, since they are largely composed of dead structures ; but 

 it must be remembered that hseniolymph is present between the 

 lamellae of the wings, and I conceive that a circulation of this 

 haeinolyniph occurs from the body to the wings, and vice versa, 

 owing to the movements of the wings and body. 



Butterflies and flowering plants afford us, both in variety and 

 brilliance, the greater part of the great boon of colour in animated 

 Nature ; both of these orders of beings are in general dependent 

 for the fulfilment of their vital functions on warmth and sun- 

 shine. The dark centre of the poppy, where the sexual products 

 are matured, is encircled by a broad open tent of crimson, which 

 flashes from its walls the most potent of the sun's rays. If we 

 are to compute the circumstances favourable to the certain and 



