Invasion by the introduced labybird beetle Coccinella septempunctata was followed by declines in native ladybird beetles in several regions of the United States, including our study sites in the inland Pacific Northwest. Subsequent invasion by Harmonia axyridis appears to have led to further changes in coccinellid communities elsewhere, although this second exotic species has just reached our area. Coccinellid larvae commonly prey upon both conspecifics and larvae of other species. We have been investigating whether patterns of intraguild predation between larvae of native and introduced coccinellids are consistent with patterns of species replacement. We have found that larvae of both C. septempuncata and H. axyridis were more likely to be perpetrators than victims of intraguild predation when paired with our two most common native species, Hippodamia convergens and Coccinella transversoguttata. Larvae of H. axyridis were especially effective intraguild predators, and so the arrival of this beetle to our region may hasten the decline of our remaining native ladybird beetles.
Species 1: coleoptera coccinellidae Coccinella septempunctata (seven spotted lady beetle)
Species 2: coleoptera coccinellidae Harmonia axyridis (multi-colored asian lady beetle)
Species 3: coleoptera coccinellidae Hippodamia convergens (convergent lady beetle)
Keywords: generalist predator, aphids
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