The Anopheles gambiae sensu lato (sl) species complex in Burkina Faso consists of Anopheles arabiensis, and molecular forms M and S of Anopheles gambiae sensu stricto (ss). Previous studies comparing the M and S forms for level of infection with Plasmodium falciparum have yielded conflicting results. Mosquito larvae were sampled from natural pools, reared to adulthood under controlled conditions, and challenged with natural P. falciparum by experimental feeding with blood from gametocyte carriers. Oocyst infection prevalence and intensity was determined one week after infection. DNA from carcasses was genotyped to identify species and molecular form. In total, 7,400 adult mosquitoes grown from wild-caught larvae were challenged with gametocytes in 29 experimental infections spanning four transmission seasons. The overall infection prevalence averaged 40.7 …