tlie colours of certain Lepidoptera. 409 



The lengths of the stages preparatory to pupation. 1888. 

 Experiments 11 — 92. 



I was very desirous of ascertaining the duration of 

 these stages, and of comparing them with V. urticce. A 

 series of experiments, with this object in view, were 

 conducted in the summer of 1888 upon the larvsB of a 

 single company (possibly a few from another company 

 may have been intermixed, although I do not think it is 

 likely), kindly brought me by Miss Bell, having been 

 found near Oxford. Others were used in the experiments 

 already tabulated (D. Experiments 43 — 47). 



The results of frequent examination are shown below : 

 the letter T indicating that the larvae had sought the top 

 of the case (Stage II.) ; S, that they had suspended 

 (Stage III.) ; P, that pupation had occurred. The time 

 beneath each such letter is either estimated or stated 

 without comment ; when stated, the change indicated 

 had been actually observed. When no time is quoted, 

 the data were not made use of in calculating the lengths 

 of stages, as was the case when the limits of error were 

 very wide as compared with the interval to be estimated. 



(See Table, pages 410, 411, 412.) 



The results of these observations are worked out 

 below, where the colours of the receptacles and the pupae 

 are also shown, the latter being carefully compared, Aug. 

 11, 1888. Two additional experiments (91 and 92) are 

 also included, the calculation being so simple that I did 

 not think it necessary to give the data from which the 

 lengths of the stages were arrived at, as I have in all the 

 other experiments. 



{See Table, pages 413, 414.) 



The 3rd pupfe of Experiments 88 and 89 were trans- 

 ferred immediately after throwing off the larval skin to 

 a white paper tioor, close to a gilt back-ground in strong 

 light. The results prove that they had ceased to be 

 sensitive. 



The lengths of the stages were subject to the most 

 excessive fluctuation, suggesting that some of the larvae 

 had quitted their food-plant somewhat prematurely as 

 the result of disturbance, while others left it in the 

 normal manner. It has been already shown, in the case of 



TRANS. ENT. SOC. LOND. 1892. — PART IV. (DEC.) 2 H 



