The occurrence and fate of the meconium and meconial peritrophic membranesin pupal and adult mosquitoes (Diptera : Culicidae)

In mosquitoes, in addition to larval and adult peritrophic membranes (PMs), a PM (meconial peritrophic membrane or MPM1) forms in the pupa around the meconium, the sloughed, degenerating larval midgut epithelium. Often, a sec ond membrane (MPM2) forms in temporal proximity to adult emergence. Differe nces in the occurrence, persistence, and timing of disappearance of the mec onium/MPMs and gas were studied by dissecting the midgut contents from pupa e of known ages postpupation and from adults of known ages postemergence. M PM1 was found in all Anopheles and Culex studied and nearly all Culiseta. T he occurrence of MPM1 varied in the Aedes species. In one series of Aedes a egypti (L.) dissections, no fully formed MPM2 was found in any specimens. T he occurrence of MPM2 appeared to be associated with adult emergence and va ried among and within the seven species studied. It typically was seen in r ecently emerged adults but was observed occasionally in old pupae. Much of our data supports the idea that MPM2 formation is stimulated by midgut epit helium distention.