Life Cycle of the Banana Weevil, Cosmopolites sordidus Germar Coleoptera:Curculionidae) on Plantain (Musa AAB group) in Humid Rainforest Agroecology of Southeastern Niger

INYANG, U.E. and EMOSAIRUE, S.O.

ABSTRACT: The banana weevil Cosmopolites sordidus is the most damaging insect pest of plantain
worldwide, A knowledge of its life cycle under the agroecology of the main production areas will provide useful information on management strategies. A study conducted in Uyo, Akwa Ibom State, under ambient temperature and relative humidity of 28±2oC and 80±2% respectively revealed the following developmental period from the egg to adult lasted 29-30 days and number of larval instars was five. Pre-ecolosion period was 6-8 days; 1st larval instar, 2-3 days; 2nd instar, 2-3 days; 3rd instar, 3-4 days; 4th instar, 3-4 days; 5th instar, 6-8 days; prepupal period, 1 day and period 6-7 days. The findings conformed to the two empirical laws of growth and development of insects. The mean growth ratio of the head capsule width C. sordidus was 1.38 thus satisfying the acceptable range of 1.2-1.4. Furthermore, when the number of instar was plotted against the logarithm of the head capsule width and body length, a straight line graph was obtained. Secondly, the body weight of the insect larvae was doubled during each instar and at each moult all linear dimension were increased by the ratio 1:26 thus satisfying Dyar’s and Przibran’s law respectively.

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