Life histories of an invasive and native ladybird under field experimental conditions in a temperate climate

Among characteristics that are thought to determine the success of invasive species, life-history traits feature prominently. However, in most cases, these have been determined under laboratory conditions. Here, we use a field set-up to determine immature development time and survival of invasive Harmonia axyridis (Pallas) and native Adalia bipunctata L. (both Coleoptera: Coccinellidae). On caged Tilia × europaea L. cv. Pallida trees (Malvaceae) with ample amounts of aphid food, we introduced freshly hatched larvae of a single or of both ladybird species and followed their development until emergence of adults. Under the condition of ample prey availability, both ladybird species apparently hardly interacted and intraguild predation did not cause significant mortality. Development time of both species is in line with data from laboratory tests under controlled conditions. Immature survival can reach high levels, but is considerably higher for H. axyridis (44-100%) than for A. bipunctata (11-77%), resulting in faster increase of H. axyridis populations, which is one of the factors that may explain its invasion success