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The food preferences of asian lady beetle Harmonia axyridis
Šenkeříková, P. ; Nedvěd, Oldřich
Survey of food preferences of Asian ladybird Harmonia axyridis included two-choice and no-choice tests. Wingless females of aphids Acyrthosiphon pisum, Aphis fabae cirsiiacanthoidis and Aphis sambuci were offered to twenty-four hours starving ladybirds. No-choice tests we conducted only with adults. We gave them 20 individuals of one aphid species and we found that ladybirds fed most number of A. pisum. In two-choice test, we combined pairs of studied species: A. f cirsiiacanthoidis x A. pisum, A. pisum x A. sambuci, A. sambuci x A. f cirsiiacanthoidis. We put 10 aphids of each of the two species combined into a plastic Petri dish and then we introduced one ladybird adult or larva. We made 20 replicates with adults. We found that there was statistical difference only in the combination A. sambuci vs. A. f cirsiiacanthoidis, where males consumed more individuals of the toxic aphid A. sambuci. For this combination, we then made 20 replicates with larvae who preyed in contrast with males more of the suitable food A. f cirsiiacanthoidis than toxic A. sambuci. We also studied the influence of contrasting background on food choice in adults. We used both tests and all combinations. We found that females did not prefer any aphid species, except for the black A. f cirsiiacanthoidis being consumed more often than the green A. pisum on black background. Because they consumed much more A. pisum in no-choice experiment on both backgrounds, the difference in choice experiment is very strong and its polarity surprising.
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