Reaction of the ladybird Chilocorus nigritus (F.) (Col., Coccinellidae) to a doomed food resource
1991
Erichsen, C. (Natal Univ., Pietermaritzburg (South Africa) Dept. of Zoology and Emtomology) | Samways, M.J. | Hattingh, V.
The coccinellid Chilocorus nigritus (F.), a predator of many scale insects, has become an economically important natural enemy of red scale (Aonidiella aurantii (Maskell)) in the subtropical citrus-growing areas of southern Africa. Although relatively easy to mass rear and distribute, there has been speculation that C. nigritus does not exploit fruit with very high scale infestations. Experimentation using an alternative prey scale Aspidiotus nerii Bouche showed that a range of low to medium-high scale population levels supported increasingly high ladybird densities. At high scale densities, where the host vegetable was imminently doomed, there was a significant drop in beetle densities. At even higher scale densities, where the fruit was already beginning to rot, there was a return in beetle densities to a level equivalent to that on medium-high scale densities. At low to medium-high prey densities, male and female beetles were present in fairly constant proportions. At high prey levels there was an increase in female dominance, yet a strong decrease in dominance at even higher scale levels where the vegetable was already beginning to rot. There appears to be an avoidance of imminently doomed vegetable hosts, yet, in contrast, rotting vegetables have some attraction but more so for males. Commercial insectary rearing of C. nigritus would be maximized by using medium-high host scale densities
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