196 SOCIAL LIFE IN THE INSECT WORLD 



penetrate to a distance one condition is indispensable : 

 the enclosure in which the captive is confined must not 

 be hermetically sealed ; there must be a communication 

 between it and the outer air. This again points to 

 the probability of an odour, although this is contradicted 

 by my experiment with the naphthaline. 



My cocoons were all hatched, and the problem was 

 still obscure. Should I begin all over again in the fourth 

 year ? I did not do so, for the reason that it is difficult 

 to observe a nocturnal butterfly if one wishes to follow it 

 in all its intimate actions. The lover needs no light to 

 attain his ends ; but my imperfect human vision cannot 

 penetrate the darkness. I should require a candle at 

 least, and a candle would be constantly extinguished by 

 the revolving swarm. A lantern would obviate these 

 eclipses, but its doubtful light, interspersed with heavy 

 shadows, by no means commends it to the scruples of 

 an observer, who must see, and see well. 



Moreover, the light of a lamp diverts the butterflies 

 from their object, distracts them from their affairs, and 

 seriously compromises the success of the observer. The 

 moment they enter, they rush frantically at the flame, 

 singe their down, and thereupon, terrified by the heat, 

 are of no profit to the observer. If, instead of being 

 roasted, they are held at a distance by an envelope of 

 glass, they press as closely as they can to the flame, and 

 remain motionless, hypnotised. 



One night, the female being in the dining-room, on the 

 table, facing the open window, a petroleum lamp, 

 furnished with a large reflector in opaline glass, was 

 hanging from the ceiling. The arrivals alighted on the 

 dome of the wire-gauze cover, crowding eagerly about 



