2 PROF. A. J. EWART ON THE 



The larvse themselves contain about the same percentage o£ water as do 

 those of allied insects, the percentages being found to vary between 68*5 per 

 cent, and 71'8 per cent. 



The lowest limits were found in quite young larvae, and in those approaching 

 the beetle stage, the percentage being highest when they are actively feeding 

 and nearly full grown. The plant specimens from which the above grubs 

 were taken contained 9*4 to 11 per cent, of water, whereas the excrement 

 collected in as fresh a condition as possible contained from 15*8 to 19"4 per 

 cent, of water. Within the parcels of plants stored in close cupboards or 

 tin cases in which these larvse were found, it is hardly possible to conceive 

 of there being a sufficient condensation of water to explain this gain in 

 moisture. It is worthy of note that the larvse seem to have a minimum 

 rate of transpiring water, for of a number placed in a desiccator, the majority 

 were still living after a week at 12° C, without any supplies of water 

 or food. 



When feeding on dried plants only two direct sources of water are available 

 for the larvse. These are the imbibed water retained in the dried material, 

 and that condensed on the surface by fall of temperature. The former 

 averages 7 to 20 per cent, in herbarium specimens, although naturally 

 higher in fresh imperfectly dried ones, and those which have been exposed to 

 moist air. 



As regards the latter source of water, careful microscopical examination 

 of feeding larvse on plants previously moistened by steam failed to reveal 

 any attempt by the larvse to squeeze out water from the material and swallow 

 it. The damper parts of the material, which are the central portions in the 

 case of freshly dried fruits, stems, and flowers, are more attacked by the 

 larvse, but these seem merely to take in the imbibed water along with the 

 material containing it. Some other supply of water appears therefore to be 

 needed to explain the high percentage in the animal's body, and the increased 

 percentage in the excrement as compared with the food. 



A possibility worthy of consideration is whether this water may not be 

 chemical in origin, being derived from the carbohydrate food and set free in 

 the animal's body by the oxidation of the carbon in respiration. 



If this were the case we should expect to find the larvse having an unusually 

 high production of COg and increasing in weight in a desiccator if provided 

 with dry carbohydrate food. 



Experiments in DEsrccATOR. 



(1) 26 grubs, two of which were very small, weighed 0'06 gramme. After 

 being for 12 days in a sulphuric-acid desiccator at 10 to 12° C. with leaves 

 and stems previously dried for several days in a desiccator at 15° C, 17 grubs 

 were living, the two very small ones appearing distinctly larger, and weighed 



