Study of the oviposition behaviour of Adalia bipunctata (L.) (Coleoptera: Coccinellidae) | Etude du comportement d'oviposition d'Adalia bipunctata (L.) (Coleoptera: Coccinellidae)
1998
Doumbia, M.
Laboratory bioassays show that gravid females of Adalia bipunctata (L.) (Coleoptera: Coccinellidae) refrain from ovipositing on substrates previously visited by larvae of their own species but not by conspecific adults or larvae of two others species of ladybird (Adalia decempunctata (L.)) and Coccinella septempunctata (L.). The deterrent effect was density dependent and mediated via a chloroform and water soluble contact pheromone present in the larval tracks. This is the first evidence of an ODP (Oviposition Deterring Pheromone) in the aphidophagous coccinellid beetle A. bipunctata. The secretion of this ODP is independent of number or nutritional status of larvae, and its effect persists at least ten days. The chemical characterization of this ODP indicates the presence of 10 n-alkanes, 21 methyl-alkanes, 6 dimethyl-alkanes and squalene. By reacting to the specific pheromone of their larvae, females of A. bipunctata disperse their offspring between patches of prey. In this way, they maximize their fitness by reducing competition between larvae and cannibalism. These results contribute to the validation of the theorical model of prediction proposed by Kindlmann and Dixon in 1993 about the oviposition strategy in coccinellids beetles. Such behaviour reduces the reproductive numerical and aggregative responses of ladybirds observed in the field to high densities of aphids. This possibly accounts for the inability of natural populations of ladybirds to control aphids efficiently. For this, the mass realease of ladybird larvae is recommended because they have an enormous predatory potential which can use to help to control aphids in an integrated control programme
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