PERMEABILITY CHARACTERISTICS OF THE PERITROPHIC MEMBRANES OF MANDUCA-SEXTA LARVAE

The in vitro permeability of the fifth-instar larval peritrophic membr anes (or peritrophic envelope) varies from larva to larva of the same age, varies along the length of the membranes within the same larva, a nd appears to vary with the age of the larva. The permeability of gluc ose through the anterior half of the peritrophic membranes, of day-2 l arvae, ranged from 2.4 to 6.2% crossing/cm2 peritrophic membranes/h. T he permeability of the peritrophic membranes from individual larvae is lower at the posterior than at the anterior end; the reduction in per meability for five larvae ranged from 35 to 53%. Although the permeabi lities of some day-2 and day-3 larvae fall within a similar range, the data suggest that the peritrophic membranes permeability falls as the larvae approach wandering.