A Peritrophic Membrane in Simulium

Abstract

Simulium damnosum Theobald is a common biting fly in many parts of Africa and an important vector of human onchocerciasis. After the female has bitten a man, the blood in the hinder part of the insect's mid-intestine forms an approximately spherical mass, which, as Blacklock¹ observed, retains its form when removed from the gut. During recent dissections, it was noticed that the blood was completely enclosed in a membrane which could not be detected in unfed flies. It was evidently produced by the wall of the mid-intestine during the blood-meal, and appeared to be a peritrophic membrane rather unlike those found in various other insects². One of the membranes, removed from the insect, was sent to Dr. V. B. Wigglesworth, who examined it and found that it gave a positive chitosan test for chitin and confirmed that it was a peritrophic membrane. He also directed my attention to the presence of a peritrophic membrane in two other Nematocera, Anopheles maculipennis³ and Phlebotomus papatasii⁴. I have found one in Simulium griseicolle Becker.