Stäubli Dreyer, B. 1995 . Biology and Feeding Behaviour of the Coccinellid Hyperaspis notato in Relation to its Prey, the Cassava Mealybug, Phenacoccus manihoti. Eidgenoessische Technische Hochschule Zuerich, Switzerland, Dr.Sc. Tech. Thesis Switzerland 95 pp.

Notes: [Dr.Sc. Tech. Thesis.] Biological and behavioural parameters of Hyperaspis notata (Mulsant) (Coleoptera: Coccinellidae) were investigated. The principal objective was to gain information which could serve as a basis for new releases of this antagonist of the cassava mealybug, Phenacoccus manihoti (Mat.-Ferr.) (Homoptera: Pseudococcidae), which had been accidentally introduced into the African cassava ecosystem. After previous releases with alternative antagonist species, H. notata could be recaptured only from certain release sites but, for unknown reasons, not from others. Overall, this predator could be established in only a few places in southern and eastern Africa. Therefore, a study of the biology and searching behaviour was planned, investigating in detail host range, innate capacity of increase, numerical and functional responses, and reactions to limited food supply. Food searching behaviour was studied in artificial arenas in the laboratory as well as in the field. H. notata from two different ecological origins in South America, namely Southern Brazil and Colombia, were compared in all experiments in order to elucidate possible differences. The food spectrum of H. notata was found to be moderately narrow, allowing survival in periods of scarcity of P. manihoti, without threatening a broad range of insects. The mealybugs, P. madeirensis (Green) and Ferrisia virgata (Cockerell) allowed H. notata survival, development, and reproduction. Aleurodicus dispersus (Russel) (Homoptera: Aleurodidae) and Aphis craccivora (Koch) (Homoptera: Aphididae) provided H. notata with food to survive a very limited time, but without reproduction. No differences between the innate capacities of increase in numbers were found between H. notata strains of two origins, Brazil and Colombia, and their reciprocal crosses. The maximum innate capacity of increase in numbers was found at the astonishingly high temperature of 30 degrees C. The capacity of increase as a function of temperature was similar to the one for the prey P. manihoti, but did not reach the same peak value. H. notata was tolerant to food scarcity. Food supply of one third of the normal supply still allowed the completion of the whole larval development, though the surviving larvae needed more time for their development. Females were able to lay eggs with only 1.2 mg cassava mealybug ovisacs per day and couple. The Colombian strain of H. notata reacted more strongly to increasing food quantity. The functional responses of larvae of both origins were the same; the Colombian females consumed more prey when the quantity of prey increased from low to moderate densities than the Brazilian females; the latter, however, fed more prey at highest prey densities. When prey was abundant, Brazilian and Colombian adults injured about 11 to 15% of the prey without consuming it. Behavioural studies on food searching in the laboratory and the field showed that the Brazilian strain tended to be more active. In general, H. notata was less active under laboratory conditions than in the field.