a1 National Institute of Agro-Environmental Sciences, Tsukuba 305–0856, Japan
Temperature tolerance was investigated in nine populations of Plutella xylostellaLinnaeus from tropical and temperate regions of Asia. At all rearing temperatures between 15 and 35°C, no clear differences were observed in female egg production or larval development between tropical and temperate populations. Thus, tropical populations did not show a high-temperature tolerance superior to that of the temperate populations. In all populations, the net reproductive rate (number of new females born per female) largely depended on the number of eggs laid per female, and egg production significantly decreased with increasing temperature (P < 0.001). Larval developmental rate also showed a significant positive correlation with temperature (P < 0.001). Per cent hatch of eggs and larval survival did not show a significant correlation with temperature: hatching was constant between 15 and 32.5°C, but considerably lower at 35°C. Larval survival was similar between 15 and 30°C, appreciably lower at 32.5°C and declined to 0% at 35°C. Based on these results, environmental conditions under which P. xylostella can maintain a high population density throughout the year in tropical and subtropical regions are discussed.
(Accepted May 19 2000)