The ookinete produced after fertilization of the Plasmodium macrogamete penetrates the gut of the mosquito and transforms into an oocyst. Within the oocyst, thousands of sporozoites form. The sporozoites eventually burst free and migrate to the salivary glands, where they await inoculation into the vertebrate host.
This photo shows an entire longitudinal section of an infected mosquito, head to the left. A portion of the gut is visible in section in the centre of the photo, surrounded by numerous small spheres, (arrow) which are the oocysts.