Date of this Version
The ventral eversible gland (VEG) of the fifth instar fall armyworm, Spodoptera frugiperda (J. E. Smith), is described and illustrated. The orifice of the VEG is a transverse slit anterior to the prothoracic legs. An increase in hemocoelic pressure everts the VEG, and the action of six pairs of retractor muscles inverts it. The VEG consists of two functionally different regions-a noneversible glandular sac lined with secretory cells, and an eversible cuticular tube which, when everted, forms a visible, external papilla. Eversion is pleurecbolic, occurring by movement of the sides of the cuticular tube rather than the apex, in response to hemocoelic pressure. A secondary glandular region occurs on the ventral surface of the everted cuticular tube. Neither the function of the VEG nor the chemical composition of its secretion is known.