Ladybird Coccinella septempunctata (Coleoptera: Coccinellidae) prefers toxic prey in laboratory choice experiment
Nedved, O.,Jihoceska Univ., Ceske Budejovice (Czech Republic). Prirodovedecka Fakulta | Salvucci, S.,University of Perugia (Italy). Dept. of Agricultural and Environmental Science
In a laboratory experiment, we investigated the preference of larvae and adults of Coccinella septempunctata for three aphid species: two essential prey, Acyrthosiphon pisum and Aphis philadelphi, and a toxic prey Aphis sambuci. Surprisingly, the toxic aphid was consumed at twice the rate of the two essential prey species. The stages and genders of the ladybirds did not differ in their preference for aphid species. In the tritrophic interaction, in the field, on the elder host plant Sambucus nigra, A.sambuci is usually avoided by C.septempunctata. To measure ladybird preference, apterous females of the three selected aphid species were released in a Petri dish followed by a ladybird. After four hours, we removed the ladybird, counted the number of aphids of each species that survived, and calculated the number of aphids of each species consumed in total. We examined preference by considering separately the first two aphids consumed by a predator (early feeding), and all remaining aphids consumed thereafter (late feeding). The consumption rates of the first two individuals did not deviate from expected values with no preference; i.e., ladybirds fed on aphids without choice in the beginning of experiment when they were hungry. The ladybirds did express preference thereafter, but our hypothesis that the ladybirds should be able to distinguish among the aphids during a later phase of the experiment and choose the most profitable species, or at least distinguish between essential and toxic prey, was rejected.
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