EIDONOMY AND ECOLOGY OF DACTYLOSTERNUM-ABDOMINALE (COLEOPTERA, HYDROPHILIDAE), A PREDATOR OF THE BANANA WEEVIL COSMOPOLITES-SORDIDUS (COLEOPTERA, CURCULIONIDAE)

Observations on the biology of Dactylosternum abdominale (Fabricius 17 92) were made in W' Kenya in banana plantations. The 3 larval instars are polyphagous predators in decomposing plant tissues where pupation occurs. Development from egg to adult [Ig] takes 17-33 days. Ig [Ig] f eed on the micro-fauna and -flora of decomposing plant tissues, on egg s and small larvae of insects and the plant tissues. Life-span is appr oximately 95 +/- 2 days. The sex ratio is 1.16 in favour of the MM. FF lay on an average 1.7 egg cases per week, each containing 4 eggs. The pre-oviposition period is 16.6 days, post-oviposition period 3 days. At unnaturally high population densities fecundity declines. Decomposi ng plant tissue is more attractive to Ig than fresh plant tissues, and banana pseudostems more attractive than banana rhizomes. In poorly ma naged fields and during the rainy seasons population densities are hig her due to the larger amount of decomposing plant tissue available. Ob served population densities: 0.5-1.8 Ig/m(2).