LABORATORY STUDIES OF LARVAL CANNIBALISM IN SAME-AGE CONSPECIFICS OF FALL ARMYWORM, Spodoptera frugiperda (J.E. SMITH) (LEPIDOPTERA, NOCTUIDEA) IN MAIZE

Abstract

Fall Armyworm (Spodoptera frugiperda) (FAW) is an economically important pest worldwide and larval cannibalism is documented as one of its significant behaviors under field and laboratory conditions. The incidence of larval cannibalism amongst same-age larvae of Fall Armyworm was investigated under laboratory conditions using 73 laboratory trials with not less than five trials for each instar stage. Each instar stage was provided with their conspecifics along with sufficient food. Direct observations were carried out in 24 hour time laps to record the missing larvae which were presumed as cannibalized. The mean cannibalism proportion was calculated for each larval stage. All larval stages except the first and second instar stages displayed same-age conspecific cannibalism. An increasing trend of the mean cannibalism proportion was observed from the third (0.16±0.04) to the fifth instar stage (0.22±0.05) with the highest value recorded for the fifth larval instars. The trend dropped at the sixth instar stage. The study suggests that larval cannibalism is evident amongst same-age larval instars of Spodoptera frugiperda, which may affect ecological relationships between organisms of a system.