Diapause and post-diapause quiescence demonstrated in overwintering Harmonia axyeidis (Coleoptera: Coccinellidae) in northwestern Europe
Raak-van den Berg, C.L. ; Jong, P.W. de; Hemerik, L. ; Lenteren, J.C. van - \ 2013
European Journal of Entomology 110 (2013)4. - ISSN 1210-5759 - p. 585 - 591.
lady beetle - photoperiodic response - winter survival - septempunctata - reproduction - temperature - netherlands - invasion - behavior - spread
The Asian ladybird Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) is regarded as an invasive species in many parts of the world. In a previous study we hypothesised that H. axyridis enters diapause at the end of October and then shifts to a quiescent state in December in northwestern Europe. In the present study we test this idea of a short, early period of diapause by sampling beetles from their hibernation sites immediately after their migratory flights in October, subsequently keeping them in outdoor cages, and then, after certain time-intervals, measuring the pre-oviposition time under optimal egg-laying laboratory conditions at 25 degrees C. We did this at both short (12L) and long (16L) photoperiods, since a photoperiodic response is an indicator of true diapause, rather than quiescence. A significant, albeit small, difference in pre-oviposition period between the two photoperiods, which disappears in December, corroborates our earlier hypothesis that the ladybirds are in a state of diapause until mid-December. Compared with that of native ladybirds the diapause of H. axyridis generally is relatively short and weak; moreover, it appears to have become shorter over the last decade. This flexibility in diapausing behaviour may be an important factor that contributes to the invasive success of H. axyridis.
Mode of overwintering of invasive Harmonia axyridis in the Netherlands
Raak-van den Berg, C.L. ; Hemerik, L. ; Jong, P.W. de; Lenteren, J.C. van - \ 2012
BioControl 57 (2012)1. - ISSN 1386-6141 - p. 71 - 84.
coccinella-septempunctata coleoptera - temperature-dependent development - hippodamia-convergens coleoptera - adalia-bipunctata coleoptera - lady beetle coleoptera - thermal requirements - pallas coleoptera - life-history - photoperiodic response - reproductive di
After establishment of Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) in Europe, population densities of native ladybird species have decreased. The post-hibernation onset of female reproduction, a key characteristic influencing population dynamics and competition with related species, was studied. Hibernating individuals were collected and transferred to outdoor cages to continue overwintering. Every two weeks a sample of individuals was transferred to long-day, warm conditions. Intensity of dormancy was studied by determining the pre-oviposition period and ovarian development. Pre-oviposition periods were short throughout our observations, indicating that Harmonia axyridis was not in diapause but in a quiescent state. H. axyridis becomes active rapidly when temperature rises in spring but is not active earlier in the year than native species. Neither the mode of overwintering, nor the onset of spring activity can explain the invasion success of H. axyridis