undergone by Insects in the Pupal State. 



305 



In the second column of the foregoing table the "actual 

 weight" is the weight of the pupa alone. In the fourth column 

 is calculated the percentage of loss upon the weight of the 

 pupa at the commencement of each of the periods. I esti- 

 mate that during the whole of its pupal existence this insect 

 lost from 25 to 26 per cent, of its weight. 



The next experiments were made upon six specimens of 

 Liparis dispar bred from eggs supplied to me in 1872 by my 

 friend Mr. G. W. Bird. These pupae were, as before, allowed 

 to remain some time before making the first weighing, and 

 were then weighed quite naked, the cocoon and larva-skin 

 being removed, so as to do away with all risk of error due to 

 drying. The weighings were in this case repeated at intervals 

 of four days, with the following results : — 



Table showing loss of weight in six pupae of Liparis dispar during 

 periods of four days. 



* signifies that the pupa is dead, t signifies that the weight is that of the imago. 

 Where no figure is supplied the imago has emerged. 



The expressions "actual weight" and "percentage of loss " 

 have in this table the same meanings as before. Specimen VI. 

 was killed by exposure to ether vapour at the termination of 

 the first period (July 14th), in order to compare the loss of 

 weight due to simple drying up with that due to respiration. 

 For this reason the dead pupa was always weighed on the 

 same days with the living ones ; and, as will be seen on refer- 

 ence to the table, it invariably lost more, from the period of its 

 death, than any of the living specimens. All the specimens 

 were kept together in the same apartment, so that they were 

 exposed to the same temperature. Nos. I., II., and III. 

 yielded perfect insects on July 20th ; no. IV. emerged on July 

 22nd, and no. V. on July 26th. This last specimen happening to 



