even metamorphosis itself, do continue more or less during the low temperature 

 treatment. If the pupae are not chilled, at least a number of them do deve- 

 lop but the time required is rather long. Diapause, therefore, is not as abso- 

 lute as it is, for example, in the cecropia silkworm (Williams, 1956). 



750 



mm^Oi/h/gm live wt 

 500 ■ 



250 



Д = average of 5 decerebraced pupae 

 о := average of 7 normal pupae 



10 



20 



30 



40 



50 



60 



70 80 



days after chilling 



Fig. 2. Comparison of the respiratory metabolism at 25"C of normal chilled pujjae with 



early decerebrated, ehileed pupae. 



Effect of decerebration. Metamorphosis is prevented by removing 

 the brain soon after pupation, in fact within two days. This corresponds 

 quite well with the results of our histological investigations, showing secretory 

 activity of the cerebral neuro-secretory cells before and after pupation (W. 

 Companjen, personal communication). 



Respiratory metabolism. In analysing the nature of diapause in 

 Bupalus, we have used the respiration intensity as a criterion for develo- 

 mental activity. 



Respiration shows the well-known U-shaped curve. Fig. 2 represents the 

 respiration of normal developing pupae compared with early decerebrated 

 items. These "permanent pupae" can survive at 25°C. for several months. 



The changes in intensity of respiration are connected with changes in the 

 amount of cytochrome oxidase, as cited in literature for several other cases 

 (e. g. Ludwig, 1953). The cytochrome oxidase activity in total homogenates 

 of pupae can be correlated with the rate of oxygen consumption. Although 

 in resting pupae the activity is low, it remains quite weU detectable. 



262 



