PHYSIOLOGY OF THE MUSEUM BEETLE. 6 



0*038 gramme ; eight grubs were dead and dried hard ; the total weight of 

 the whole 25 being 0*05 gramme, a loss of weight of O'Ol gramme. 



Assuming that the dead and living grubs averaged the same weight at 

 first, the living grubs have gained 0*0016 gramme in weight (0*038 — ^^- x 0*06 

 = 0*0016). The dead grubs showed no signs of external injury, but 

 nevertheless the possibility remains that the moisture exhaled from them 

 may have been condensed and absorbed in some way by the living grubs. 



(2) The 17 living grubs weighing 0*038 gramme were returned to the 

 desiccator with the plant material, and after 14 days at 8 to 10° C, 12 remained 

 living and capable of moving. They weighed when brushed clean 0*028 

 gramme. This equals an apparent gain in weight on the above assumption of 

 0*0016 gramme (0*028 x^| — 0"038), the two smaller grubs being still living. 

 As before, however, this moisture may have been gained from the dead 

 grubs, for the twelve living and five dead and shrivelled ones weighed 

 altogether 0*033 gramme, a loss of weight of 0*005 gramme. On the other 

 hand, the loss by respiration has to be considered, for judging from the amount 

 of excrement the grubs fed little or not at all upon the desiccator dried 

 material, and seemed rather to devote their energies to protecting themselves 

 against transpiration. 



(3) Respiration. — The remaining 0*028 of a gramme of living grubs were 

 placed in 2*5 c.c. of air for 18 hours at 8 to 10° C, and the residual gas 

 analysed in a Bonnier and Mangin gas apparatus. No measurable quantity 

 of carbon dioxide was present, probably as the result of the poisonous action 

 of the mercury, the grubs being dead at the end of the experiment. 



(4) 25 medium-sized active grubs weighing 0*083 gramme were placed, 

 with 1*044 gram of plant material dried, in a desiccator at 10° C. until 

 a constant weight was reached. A similar amount of plant material tested 

 in the same way still contained 4*8 per cent, of moisture, or at least lost that 

 weight when heated to 100° C. for 8 hours, so that the 1*044 gramme may 

 be taken to still contain 0*05 gramme of water. 



After 14 days in a desiccator at 8° to 10° C, the total loss of weight was 

 0*092 gramme. 22 living grubs weighed 0*063 gramme, and with the three 

 dried and shrivelled ones, 0*072 gramme. The living grubs apparently there- 

 fore lost 0*012 gramme in weight (0*083 — 0*063 x ||), while the apparent loss 

 converted into CO9 would be 0*0084 gramme. 



The 0*063 gramme of living grubs were sealed in a tube with 1*6 c.c. of air, 

 and after 24 hours were found to have produced at 8° to 10° C, 0*000525 

 gramme of carbon dioxide, which in 14 days gives a total production of 

 0*0024 gramme, which is less than one-third the apparent loss. The difference 

 of 0*006 of a gramme is partly due to the loss of water by dead grubs, and 

 partly to respiration being more active at the commencement of the 

 experiment. The relative activity of respiration may be seen from the 

 following table : — 



