Life cycle of malaria parasites within the mosquito vector (sporogeny). Timings show approximate estimates of the stages post blood meal (pbm) for the progression of P. berghei though Anopheles stephensi. Apoptosis has been observed in three species of malaria parasites at the ookinete stage. The ookinete to oocyst transition is a well known bottleneck in the parasite life-cycle. Estimated reductions in numbers at this point in the life cycle are variable but for P.berghei in A. stephensi one estimate is a 35 to 120 fold reduction in parasite numbers depending on the density within the vector .