406 Mr. F. Merrifield and Mr. E. B. Poulton on 



I found this species very troublesome as to the place of 

 its pupation. In no one case did I succeed in getting it 

 to pupate on a stick whatever its colour, and it had a way of 

 pupat'ng on the clear glass in front of the cylinder or bottle. 

 To circumvent it I procured some white photographic 

 trays, some of which I covered with orange glass, and 

 others with deep green glass, while one was lined with 

 black paper and covered with clear glass, and another, left 

 white, was covered with clear glass. The space left 

 between the bottom of the tray and the glass covering varied 

 from about ^ inch to | inch or a trifle more, and in some 

 cases it will be seen the pupa bears marks of squeezing. 

 These instances are indicated by tlie word "screen," in the 

 case of trays thus provided with screens of coloured glass, 

 " tray " where the covering was clear glass. 



The whole of the pupae obtained (about 80) are displayed, 

 part in the Exhibition Case, and part in the glass-topped 

 boxes. 



2. Results of the above Experiments. (E. B. P.) 



The pnpge of P. hrassicx were compared May 3rd and May 

 6th, 1899, the results being shown in the following table (see 

 pp. 407, 408). The degrees of pupal colour are the same 

 as those suggested and fully described in Phil. Trans. 1887 

 (/. c. pp. 409, 410). The letters g. o. w. y. indicate the faint 

 greyish green, orange, yelloto, or tvhite tint of the pupse in the 

 darker degrees. The tint is however usually very faint, 

 being greatly obscured by the dark pigment (see also 

 Trans. Ent. Soc. London, 1892, p. 439). 



These results afford a very useful confirmation of 

 those which have been previously obtained. Thus the 

 hlctch (1, 2, 3) produced uniformly dark pupae, the effect 

 being as strong when the dark surface was behind glass (3) 

 as when it formed the surface to which the pupa was 

 attached (1, 2). The black surroundings also produced a 

 considerable effect upon pupse which were attached to the 

 clear glass at some distance (4), 



Darkness (5) produced far more intermediate pupse, 

 although still upon the dark side of intermediate. As Mr. 

 Merrifield has suggested, this result is to be compared in an 

 interesting manner with that of elear glass (28). It is 

 probable that in these two cases we witness the results of 

 pupal tendencies undirected by any effective stimulus. 



