Field Biology of Epilachna punctipennis Muslant (Coleoptera: Coccinellidae) a major defoliator of bitterleaf, Vernonia amygdalina Del. in southwestern Nigeria


ABSTRACT: The foraging behaviour and life cycle parameters of Epilachna punctipennis on the bitterleaf, Vernonia amygdalina were investigated in the field and in the laboratory at ambient temperature and humidity. E. punctipennis appeared to be a diurnal folivore and the adults were most active in cool and bright daylight condition. Adults did not fly often and mating took place on both adaxial and abaxial surfaces of leaves of V amygdalina. Copulation occurred more than once in the adult. Eggs were deposited by the females in about 10 clusters of 25 eggs and glued firmly on to the
adaxial surface of very young leaves. Actual fecundity per female averaged 218 eggs per lifetime. Unmated females laid very few eggs and these did not hatch. The first and second instar larvae fed on young leaves but migrated later to older leaves at the third instar. Adults and the immature stages were commonly distributed spatially on each branch at the uppermost 5-10 leaves from the apical bud. All the feeding stages were phytophagous . The life cycle consisted of an egg, four larval instars, a pupa and the adult. All larval stages lasted an average of five days except the fourth instar,
which lasted only four days. The mean growth ratio was 1.46. The potential of the beetle to cross on to other feeding sites and cause damage to the host plant increased with age of the insect.

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