PHYSIOLOGY OF THE MUSEUM BEETLE. 



Organism. 



Grubs after 14 days in | 



desiccator ( 



Potatoes 



Man 



Dog 



Horse 



Fresh actively feeding I 



grubs i 



Frog 



Tench '.'.....'.'.'.'.'.'...'... 



Cray-fisli 



Cockroach 



Earthworm 



* These values are probably too high, the larvae being heated to 100° C. at the close of 

 the experiment so that all the COo contained in their bodies was driven out. 

 t Some of the numbers are from values supplied by Prof. Osborne. 



When actively feeding, the respiratory activity of the grubs is even at low 

 temperatures nearly as high as that of a warm-blooded animal, but a part of 

 the CO2 produced may be due to bacterial action in the alimentary canal. 



Bacteria are present in abundance in the alimentary canals of actively 

 feeding grubs, and since these bacteria feed on the carbohydrate food and 

 oxidize its carbon under conditions where no transpiration of water as vapour 

 is possible, a certain increase in the percentage of free water in the alimentary 

 canal must be produced in this way. This may be the explanation of the 

 slight rise observed in the percentage of moisture contained in fresh excreta as 

 compared with the food, but it is uncertain whether the larvse absorb internally 

 any of the moisture set free in this way. 



It follows from the above data that under unfavourable conditions as 

 regards temperature or the supply of moisture and food, the respiratory 

 activity of the grubs is reduced considerably. At the same time the loss of 

 moisture is largely controlled by the living animal, for in a desiccator, dead 

 grubs dry rapidly, whereas living ones retain their moisture for a long time 

 even when no apparent external supply of moisture is available and when 

 not actively feeding. They cannot live for more than a limited space of 

 time in dry air on material containing less than 10 per cent, of water, and 

 may lose more than 10 per cent, of their moisture within a fortnight in a 

 desiccator. 



When actively feeding and respiring, the oxidation of the carbon in their 

 carbohydrate food sets free a certain amount of water which, aided by the 

 imbibed water- retained in the plant-tissues, suffices, if the latter is over 10 per 

 cent, in amount, for their aqueous requirements. The grubs do not seem to 



