The Litomosoides chagasWlhoi helminth was studied as a model for microfilaria invasion of the midgut of Culex quinquefasciatusmos-quito, vector of Wuchereria bancroftihelminth, causative agent of the human Wlariasis. Histology and transmission and scanning electron microscopy were utilized to show the topography of mosquito midgut invasion by the helminth. An analysis of midguts dissected at difereent time points after a blood meal demonstrated that the microfilariae interacted and crossed the peritrophic matrix and the midgut epi-thelium of C. quinquefasciatus. The microfilariae invaded preferentially the mosquito abdominal midgut and the invasion process occurred between 2 and 3 h after the blood feeding. In some cases, microfilariae caused an opening in the midgut that separated the epi-thelial cells, while in others cases, the worms caused the detachment of cells from the epithelium. Ultimately, L. chagasWlhoi crossing activity appeared to damage the midgut. It was also observed that the microfilariae lost their sheaths during their passage through the Wbrous material of the peritrophic matrix, before they reached the midgut epithelium. Since the exsheathment process is necessary for the conti-nuity of larvae development, it seems that the passage through the peritrophic matrix is an important step for the parasite’s life cycle. This experimental model revealed details of the interaction process of helminthes within the vector midgut, contributing to the knowledge of factors involved in the vector competence of C. quinquefasciatusas a vector of Wlariasis.