Temperature‐dependent development and immature survival of an aphidophagous ladybeetle, Propylea dissecta (Mulsant)

Development and survival of the immature stages of an aphidophagous ladybeetle, Propylea dissecta (Mulsant) was investigated at five constant temperatures, viz. 20, 25, 27, 30 and 35°C, using Aphis gossypii Glover as prey. Developmental period of all the life stages were significantly affected with change in constant temperature and developmental rate increased with increase in temperature. Theoretical lower thermal threshold for complete development and thermal constant was 10.39°C and 465.11 Day‐degrees, respectively. Of the various life stages, first instar larvae were most susceptible to mortality at temperatures between 20 and 30°C, whilst pre‐pupae suffered least mortality. Egg‐mortality was maximum at 35°C. Female biased sex ratios were obtained at all five temperatures tested with higher proportion of females at the extremes of temperature, thus suggesting that females are more thermal‐tolerant. Lowest mortality of immature stages with maximum larval survival and adult emergence was recorded at 27°C, while reverse was the case at 35°C. Thus, 27°C may be considered best for the laboratory rearing of P. dissecta.