Exposing eggs to high temperatures affects the development, survival and reproduction of Harmonia axyridis

• Heat stress on Harmonia axyridis eggs reduced hatching rates.
• The subsequent effects of heat stress on eggs result in longer larval development time and lower survival rate.
• Heat stress on eggs also increased weight, lowered reproduction, and shortened longevity of H. axyridis adults.

The multicolored Asian lady beetle, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), is a well-known biological control agent for aphids and soft-bodied insects. We investigated the developmental, survival and reproductive traits of H. axyridis when its eggs were exposed to 25 (control), 37, 39 and 41 °C for 1 h, and then transferred to ambient condition (25 °C). The effects of heat stress on the hatching success greatly differed among temperature treatments. No H. axyridis larvae hatched out at 41 °C. The development, survival, weight, reproduction and longevity of H. axyridis exhibited significant differences with temperature treatment and gender. The survival rate of immatures declined, while the adult fresh weight of both sexes markedly increased with the increase of temperature. Heat exposure of the eggs caused a subsequent reduction in longevity, oviposition period and reproduction, while the pre-oviposition period became longer as the temperature increased. These may imply that the reproductive investment increased in higher level stressful environments, and the response of adult individuals could be linked to the experiences from early stages of the life history. Our findings provide useful information for predicting population dynamics and understanding the potential for H. axyridis as a biological control agent under variable environments.