TEMPERATURE AND METABOLISM 



219 



falls for some days, and finally rises again, the final rise being 

 possibly partly due to muscular movement within the nearly 

 mature pupae themselves, which is preparatory to the emergence 

 of the imagines. The same general conclusions were arrived at 

 by Taylor (1927) with reference to the COj production of certain 

 dipterous and Lepidopterous pupae, but in some species a marked 

 depression was noted just before the time of emergence — a feature 

 not previously noted by other observers. Krogh determined the 

 CO 2 output of pupae of the beetle Tenehrio molitor at different 

 temj^eratures from 21° to 33° C. (Table V.), and concluded that 

 the total metabolism, as judged by this criterion, was constant 

 over the range of temperatures given for individuals of uniform 



Table V. COg Production by Pupae of Tenehrio molitor. (From 



Krogh.) 



weight.^ Krogh also showed that the relation between tempera- 

 ture and COg output could not be satisfactorily expressed by 

 van't Hoff's coefficient, and that between 20-9° and 27-25° C. 

 the increment in COg production was proportional to the 

 temperature : above 27° it decreased, as did the velocity of 

 development. Peairs (1927) also advanced some evidence that 

 the amount of CO2 produced during the pupal instar of the fly 

 Calliphora vomitoria is near a constant, irrespective of temperature, 

 and he suggests that departures from the constant may represent 

 basal metabolism not directly associated with the developmental 

 processes. On the other hand, Northrop (1926) found that the 

 amount of COg produced by Drosophila is not constant for either 



^ Similar observations made by him on the eggs of the water beetle Acilius 

 showed that a fixed amount of CO2 is produced during their incubation. 



