206 



SOME ASPECTS OF ECOLOGY 



50" 



35' 



>ZON£ OF F/iT/^L HIQH TEMPERyiTUIZE 



'ZONE OF /N/^CT/\//TY 



Temperature 

 The General Subject. It is well known that temperature 

 exercises a profound influence upon insects in diverse ways, and 

 their relations to this factor have been subject to more adequate 



experimentation than any 

 QO^rr^-^M/^xiMUM F^Ty^L TEMPEftATuR£ othcr physical agcucy. The 



most comprehensive recent 

 work on the subject is that 

 of Belehradek (1935), which 

 deals with it from the 

 general biological stand- 

 point. 



The extremes of tem- 

 perature limit insect 

 activities both in space 

 and time. Their rates of 

 metabolism and, conse- 

 quently, those of growth, 

 reproduction and general 

 behaviour, are largely con- 

 trolled by temperature. A 

 given species of insect is 

 active within certain limits 

 of temperature which form 

 the zone of effective tem- 

 perature (Fig. 66). Above 

 the maximum effective 

 temperature there is a zone 

 of inactivity, or heat- 

 dormancy, from whose 



Fig. 66. Temperature zones in relation to effects the insect recovers 

 the activities of the cotton-boll weevil. i j j. 



(According to Hunter and Pierce.) ^hcn removed to more 



favourable conditions. 

 Above this zone of inactivity, there follows a range oi fatal high 

 temperatures at which death supervenes after the lapse of a certain 

 interval of time, according to each temperature. At the maximum 

 fatal temperature death is rapid and almost immediate. On the 



13-3* 



•ZONE OF £FFECTI'/E T£MPEf^TU/^E 



'^'.THRESHOLD OF DEVELOPMENT 



>ZOHE OF /N/tCT/y/TY 



4-4' 



'■ZOME OF Fy^T/lL LOh^ TEMPE/^/^TURL 

 \Z'Q''Vr-'' MINIMUM F/imL TEMPER/^TURE 



