Oyi Suhfitance-waste in Insect Pupce.. 301 



XL. — On the Amount of Substance-waste undergone hy 

 Insects in the Pujml State ; with Remarks on Papilio Ajax. 

 By Raphael Meldola, F.C.S. 



The observations herein recorded are preliminary to an ex- 

 perimental inquiry into the law which governs the size of the 

 individual in species undergoing complete metamorphosis. 

 Being unable to continue the investigation until next season, 

 when some species going through its larval and pupal stages 

 within the season will be procurable, I deem it advisable to 

 make known the results of my experiments so far as these are 

 at present conducted. 



The ideas that have led to this inquiry are briefly these : — 

 From the period of its emergence from the &^^ to the assump- 

 tion of the pupal state the larva of an insect undergoing com- 

 plete metamorphosis continues to feed and to increase in bulk ; 

 in this stage the insect exerts but little activity, so that nutrition 

 is in excess of waste and a considerable surplus is left for 

 growth. With the pupal stage comes a period of quiescence, 

 when the substance-loss due to activity is reduced to a 

 minimum. 



The experiments of Newport * have shown that in the pupal 

 state respiration still goes on, though to a diminished extent, 

 so that the carbonic acid and water excreted by the pupa, being 

 uncompensated by food, must be a dead loss of matter to the 

 insect. Several weighings made by Newport prove the truth 

 of this statement. Thus, there being gain of matter in the 

 larval state and loss during the pupal stage, and there being, 

 moreover, undoubted variation in size among the individuals 

 of a species (apart from sexual difference in size), it occurred to 

 rae as probable that one of the laws governing individual size 

 was to be derived from the facts above set forth ; for from 

 these we might fairly expect that the size of an individual (all 

 disturbing factors being eliminated) would be, ceteris paribus, 

 inversely proportional to the ratio of the pupal to the larval 

 period, or directly proportional to the ratio of the larval to the 

 pupal period. 



Such being the law arrived at h priori, I determined to 

 submit it to experimental investigation when a favourable 

 opportunity presented itself. In the mean time, when searching 

 for recorded facts bearing on the subject, I became acquainted 

 with the interesting experiments of Mr. W. H. Edwards f upon 



* Phil. Trans. 1836 & 1837, vols, cxxvi. & cxxvii. 



t ' Butterflies of North America,' part ix., Dec. 1871. I am indebted 

 to my friend Mr, A. G. Butler, F.L.S., for the loan of this work and also 

 for specimens of P. Aj'ax. 



Ann. & Mag. N. Hist. Ser. 4. Vol.xn. 21 



