Biology of Reduviidae of Cocoa Farms in Ghana

Abstract

In the cocoa farms the members of family Reduviidae are distributed in a variety of habitats associated with particular food, defense and breeding requirements for various species. In general the ectrichodiines are exclusively litter dwellers and reduviines occur only under the loose bark of primary forest trees. The members. of subfamily Harpactorinae are associated with herbs, shrubs and the foliage of cocoa trees. A group of harpactorines comprising Authentac, Margasus, Nagusta and Odontogonus has been found to be completely arboreal. The food and feeding behavior of the cocoa farm Reduviidae were explored and data on the insects preyed upon by the Reduviinae obtained for the first time. Iff one locality at Tafo, one species of this subfamily utilized 24 different species of ants belonging to four subfamilies. As a preliminary to feeding, the reduviids were generally observed to exhibit grooming behavior which at times was repeated once the bug had finished feeding. Coloration, mimicry and scent glands were considered to contribute greatly to the primary defense of the Reduviidae found in the cocoa farms. The majority of Reduviidae living in cocoa canopy or concealed situations such as leaf litter tended to be dark-colored, usually matching their surroundings. The reduviids at shrub level are conspicuously colored and their adults exhibit a behavior pattern highly suggestive of certain wasps. Excepting the Emesinae and Tribelocephalinae, where the scent glands are completely absent, repugnatorial glands producing generally a pungent secretion were found in all the reduviidae occurring in cocoa farms. A unique system of glands situated at the base of dorsoabdominal hairs was discovered for the first time. This system produces secretions which assist in sticking camouflage material to the back of reduviine larvae. Early instars of some species of Harpactorinae were observed to mimic smaller species of ants such as Pheidole and Anochetus. Courtship, mating and oviposition in Reduviidae were studied and the significance of the precopulatory riding position, parental care and laying of eggs singly or in groups is discussed. Cocoa capsids are attacked by a number of parasites and predators including ants, reduviids (assassin bugs), mantids, long-horned grasshoppers and crickets. Williams (1954) showed that predators are a significant factor in the natural control of capsid numbers. He furnished quantitative data which suggested that the assassin bugs and mantids together account for more than one and a half times the capsid mortality caused by ant predation. Leston (1969), however, considered that ants afford considerable protection to cocoa trees against capsid damage. Marchart (1969), on the other hand, presented experimental evidence in support of his contention that ants are ineffectual against capsids. One point which is very clear from the work of these authors is that each predatory species individually causes an appreciable mortality of the capsids. Smith (1968) has stressed that it is these partial controls that are so important in integrated control programs. 1 Present address: Abidjan, P.O. Box 1604, Ivory Coast.