Ecology and Behavior of Cocoa Pollinating Ceratopogonidae in Ghana, W. Africa

Abstract

Close spacing of Theobroma cacao L., shade trees with large buttresses, and various ground substrates are essential to attract pollinating ceratopogonids to cocoa plantations. The midges breed throughout the year in Ghana, but their numbers fluctuate monthly as well as yearly depending upon the amount of rain. The most favorable weather for flight is under cloud cover. Different species have different sex ratios which can be determined only by breeding a large number of individuals. Loose batches of eggs are deposited in concealed recesses of moist, decomposing plant debris, as larvae feed on molds and fungi that grow on these media. Ceratopogonids are gregarious throughout life. Swarming activity enables males to find mates and females to oviposite. Mating takes place in flight. Dispersal flight, occuring twicedaily, is multidirectional and limited to 5–6 m at a time. Of some 70 species of Ceratopogonidae found in Ghana, only 8 including 4 species of Forcipomyia , 2 species of Stilobezzia , and a species each of Culicoides and Atrichopogon , are common in cocoa flowers. Effective pollination by these insects is by no means simple; an average of 27.0% (6.5–60.0) of the total number of effectively pollinated flowers between February 1971 and December 1973 were attributed to these midges.