lOO YORKSHIRE NATURALISTS UNION 



own members as have the larvae. But those who have paid 

 much attention to the egg^s of butterflies and moths, have found 

 that the diversity in form and colour in birds' egg^s, great as it 

 appears to be when we see a larg-e and well arrang^ed collection, 

 becomes absolutely insig^nificant in comparison with the beauty, 

 both in form and desig"n, in those of insects, and those 

 thoroughly conversant with them, can tell on seeing" an insect's 

 egg", just as surely as can the oologist on seeing a bird's eggy 

 the exact species to ^vhich it belongs ; it seems not unlikely, 

 indeed in some genera it has already been attempted, that 

 classification of species will in the future be based largely on 

 the form and structure of the egg. 



Dr. Chapman, Mr. F. Merrifield, and others, too, have 

 shewn us of what scientific importance are the pupae, and the 

 results of the experiments of the latter gentleman, from the 

 aspect of protection of species, have been very extraordinary. 

 An exhibit by Mr. Merrifield at the meeting of the London 

 Entomological Society on October 5th, 1898, was the most 

 remarkable thing of its kind I have ever seen. Mr. Merrifield 

 had obtained a large quantity of the larv^ of Pieris 7iapi\ one 

 of our common white butterflies, and when nearly full fed had 

 enclosed a considerable quantity in each of a large number of 

 diff"erently coloured receptacles in such a way that they were 

 forced to pupate on the particular colour of glass or paper, etc., 

 in which they were enclosed. The result was most striking, 

 With a ver)^ small percentage of exceptions, these larvae (and 

 it must be remembered that all the larvae were pretty much 

 alike in appearance) which had pupated on a green surface pro- 

 duced bright green pupae ; those on gold coloured or gilt surfaces 

 were yellow ; those on stone colour, grey ; and most remarkable 

 of all, those on white paper were white, and, so far as I 

 observed, quite devoid of markings. A better instance of 

 assimilation to the colour of the environment could not be. All 

 these pupae would of course remain as such through the winter, 

 and it will be at once grasped how a far higher percentage of 

 them would, if at large, escape the prying eyes of birds, when 

 similar in colour to the substance they were attached to, than 

 would be the case if, when at the change to pupae, the colours 

 were thrown hap-hazard, resvilting in a green pupa being on a 

 white ground, a yellow one on a stone ground, etc. 



Another interesting item came out in the course of the dis- 

 cussion, and after conversation on these pupae. The very closely 

 allied and still commoner Pieris 7'apce is, like P. napi, a double- 

 brooded species, and its autumn larvae produce pupae varying in 

 colour in just the same way as do those of P. napi ; but it was 

 elicited that the larvae from the spring brood, which have only 

 to pass a fortnight or so in the pupal stage, do not leave the 

 green plants on which they have fed, but change to pupae on 

 them — the pupae in that case being almost invariably green. 

 But on the other hand the larvae of the autumn brood, 



