Foraging behaviour of predaceous ladybird beetles: A review
Keywords:aphids, Coccinellidae, cues, searching behaviour, semiochemicals
We review the foraging behaviour of predaceous ladybirds in the light of current knowledge. Ladybirds should forage optimally to maximise their resources; however, they are limited – among other things – by their poor visual acuity. Ladybird foraging behaviour includes location of the habitat of its prey, location of prey and prey-selection. Chemical cues are important in locating the habitats of their prey. This is further driven by volatiles or semiochemicals emitted by injured plants, particularly in response to attack by herbivores. Various chemicals induce positive electroantennographic responses in ladybirds that guide them to prey sites. Honeydew secreted by aphids along with alarm pheromones or kairomones act as secondary chemical cues that narrow the search from extensive to intensive and help in prey location. Visual cues further aid prey-location and enable foraging adults to locate areas with patchy or abundant prey. Thereafter, ladybirds select their prey, which starts with random attacks that result in prey selection in terms of size and palatability. Prey selection seems to be host plant driven, i.e. aphids sequester host plant chemicals, which are imbibed by ladybirds. This is evident from the fact that nutritious prey cultured on toxic host plants are usually less preferred or rejected. Foraging ladybirds, especially larvae, can perceive ladybird footprints or odours that deter them from foraging. The above information could be useful in biocontrol programmes in which foraging ladybirds are manipulated by using chemicals as attractants or rearing aphids on nutritious host plants.
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