Final Report Summary - VECSYN (Synthetic species of the mosquito vectors of human disease: from hybrid genetics to a new type of vector control) The aim of VecSyn was to study natural mosquito species hybrids, generate artificial species barriers as well as to develop transgenic mosquito strains for controlling malaria transmission. We have explored the evolution of closely related mosquito species, the biology of their Y chromosomes and demonstrated the feasibility of Y hybrid strains. We then developed genetic sexing strains based on these labelled Y chromosomes that will be used to underpin mosquito control by the release of sterile males. We have demonstrated, using a CRISPR/Cas9 activate & mutate approach, how artificial reproductive barriers can be erected and we have contributed to the generation of other genetic control tools for the malaria mosquito such as gene drives and sex distorters. We have also characterised new molecules that can block the development of the Plasmodium parasite in the mosquito vector as well as developed an improved membrane-feeding assay for testing such molecules in the future.