the culours of certain Lepidnptera. 365 



I have previously spoken of the period before pupation 

 as the " preparatory period," and have pointed out that 

 it consists of three stages : — 



" Stage I., in which the larva quits its food plant and 

 hurries about, seeking for some place upon which to 

 pu])ate. 



Stage II,, in which the larva rests motionless upon the 

 selected surface, and towards the end of the stage spins 

 the boss of silk for its subsequent suspension. 



Stage III., in which the larva hangs suspended by its 

 posterior claspers from a bo.-s of silk " (Phil. Trans., 

 1887, B., pp. 327, 328). 



If we assume that Stage I. began with the shock of 

 capture in the case of the first three larvre to pupate in 

 each of the three receptacles without food, the following 

 table indicates the beginnings and ends of all the stages 

 and preparatory periods which could be safely fixed. 



{See Table, x>ages 366, 367.) 



The first point brought out by these figures is the 

 great difference between the lengths of the stages, ac- 

 cording as the larvae remained upon the food -plant, or 

 were wandering at the time the experiment began. 

 Stating the results approximately, this difference is 

 more clearly shown by the following arrangement : — 



{See Table 1, page 370.) 



It is here seen that the great difi'erence between the 

 length of the period before pupation in A, C, E, and B, 

 D, F, is almost entirely due to the immensely greater 

 duration of Stages I. and II. in the former, Stage III. 

 being approximately the same throughout. 



My former conclusions as to the lengths of the stages 

 before pupation were chiefly founded upon experiments 

 which resembled A, C, E, rather than the others, and 

 hence this comparison has an important bearing on the 

 recorded results, which were summarized as follows : — 

 " The larva; wander for a variable time, then rest for 

 about 15 hours upon the surface selected for pupation, 

 and finally hang suspended, head downwards, for about 

 18 hours, after which time pupation takes place" (Phil. 

 Trans., I.e., p. 438). The estimates arrived at above are 

 much smaller, especially in the larvae provided with food, 



