Movement, feeding behaviour and growth of larvae of the sorghum shootfly, Atherigona soccata

Movement, feeding behaviour and growth of larvae of the sorghum shootfly, Atheriyona saccata, were studied under controlled conditions on a susceptible sorghum variety, CSH-1. The time of hatching coincided with the presence of moisture on the leaf, a condition favourable to movement of the larvae to the base of the leaf. Cutting of the central shoot at its base by the larva caused the symptom referred to as ‘dead heart’. The three larval instars are described and changes in the cephalopharyngeal skeleton discussed.

Movement of the larva to the base is not due to positive geotaxis. Larvae in plants placed horizontally to the ground did not develop normally and a high mortality resulted. The larvae are strongly cannibalistic inside the host-plant but not outside of it. The first-instar larvae do not migrate from one plant to another, but the third instars may do so if the source of food is exhausted.