Weight dynamics in females of invasive and autochthonous populations of Harmonia axyridis (Pallas) (Coleoptera, Coccinellidae) during the induction of reproductive diapause

Under natural conditions, predatory insects often faced the shortage of food caused by an increase in the predator population density and/or a decrease in the prey population density. Experimental studies demonstrated that females of two laboratory strains that originated from autochthonous (the Russian Far East) and invasive (Krasnodar territory of Russia) populations of the aphidophagous ladybird beetle, Harmonia axyridis showed two responses to the absence or shortage of aphids. The first response, termination of oviposition, was observed in several days after transfer to the poor diet, it was independent of photoperiod, and it was stronger in females of the invasive line. The second response, induction of reproductive diapause, was observed in 20 days after transfer to the poor diet, it interacted with the long-day photoperiodic response, and it was stronger in females of the autochthonous line. The induction of reproductive diapause (in comparison with a simple termination of oviposition) is a more basic and less easily reversible physiological process. Thus, we conclude that under natural conditions, females of invasive populations terminate oviposition with the first signs of a shortage of aphids more quickly than females of autochthonous populations and also more quickly start oviposition again with an increase in prey population density. Possibly, these features can be considered as adaptations to new, less stable and less predictable environmental conditions. DOI: 10.1134/S0013873816080029