Woodside. 45 



the white butterfly cannot distinguish between a piece of 

 white paper and a lady of its own kind ; but so, at first, it 

 really was, and only a close inspection with its antennae 

 enabled it to discern the difference. 



If you examine carefully the butterfly which you captured, 

 you will find that its eyes are large and well developed ; each 

 consists really of quite a mass of eyes, all bound together, 

 each of which has a separate hexagonal facet, the surface of 

 the compound eye being strongly convex. Yet with such an 

 apparently well-developed eye, the organ as an optical in- 

 strument is very defective ; practical experiment has proved 

 that with the exception of a remarkable power to discrimin- 

 ate masses of colour, of a keen appreciation of slight differ- 

 ences of light and shade, and of an ability to recognise objects 

 in motion, the eyes of most insects are practically useless, 

 and so far as the sight of the white butterfly is concerned, we 

 have seen that it is attracted by anything of its own colour 

 as quickly as by a female of its own kind. 



You may let the butterfly go now, and watch the female 

 fluttering along the hedge. Every white or yellow flower 

 appears to attract her. She hesitates, stops, hovers, but goes 

 on, then slackens again for a moment, and at last comes 

 to a final stop on a leaf of hedge mustard. Her body is 

 thrust down on the leaf and then quickly raised again. She 

 passes to another leaf and then flutters off, again hovering 

 over a variety of flowers, never settling though until another 

 cruciferous plant is detected, and then down goes the abdomen 

 and another egg is deposited. Never by any chance is the 

 insect at fault ; no egg is laid except on a plant that will 

 serve as food for the young caterpillars. Even to us many of 

 the plants appear to be very much alike, and if the insect 



