of certain lepidopterous larvce and jJupce. 51 



colours, green and brown. {E. orhicularia is variable, 

 E. pendidaria regularly dimorphic, E. omicronaria di- 

 morphic, with a great difference in the relative numbers 

 of the two forms. Some, if not all, of the other species 

 are also dimorphic, but I have not had the opportunity 

 of observing them closely). 



The interesting, and, as far as I know, unique, point 

 about this dimorphism is that it extends into the pupal 

 state, and thus seems to prove a permanence of the 

 condition which is irreconcilable wiih Prof. Weismann's 

 view. The brown larvae always become brown pupae, and 

 the green larvfe green pupae. I have never known an 

 exception to this (see figs. 9 and 10 for the green and 

 brown pupae of E. omicronaria, figs. 11 and 12 for those 

 of E. pendidaria). There is, however, no extension 

 of this pupal dimorphism into the imago stage. It has 

 nothing to do with sex. This is shown by the following 

 figures : — I possessed 43 pupae of E. pendidaria of the 

 first summer brood of 1883. Of these 30 were green 

 (producing 17 males and 13 females), while 13 were 

 brown (producing 5 males and 8 females). Many of the 

 next generation of pupae also emerged, forming a second 

 summer brood. Of these (40 in number) 27 were green 

 (13 males and 14 females), while 13 were brown (7 males 

 and 6 females). Furthermore, there is no distinctive 

 mark by which it is possible to identify the imagines 

 from either set of pupae. Hence it appears certain that 

 the larval and pupal dimorphism is of advantage in 

 these stages only, and has no further significance in the 

 ultimate stage. 



This seems to be true of nearly all eases of dimorphism 

 (although in some few instances it is sexual : see note to 

 pages 308, 309 of Prof. Weismann's book). This advan- 

 tage I believe to be a direct result of dimorphism. It is 

 of value to a larva and pupa (if exposed) to be divided 

 into two groups, coloured respectively with the two most 

 protective tints. It is certainly a protection to the 

 species against the keen sight of entomologists. It is 

 well known by every collector of larvae that it is often 

 difficult to find a larva for the first time, but that after 

 this it is comparatively easy to find more. In colloquial 

 phraseology the eye "gets in" for that particular species. 

 And I believe that this is true (although to a much 

 smaller extent) for each day's work at larva-hunting. 

 I think that everyone who has tried to find a larva, 

 which he only knows by book description, upon its 



