A successful application of the sterile insect technique and other strategies designed to eliminate large populations of insects relies on the efficient releases of competitive, sterile males into the natural habitat of the target species. As released sterile females do not contribute to the sterility of population in situ, systems for the separation of male from female individuals are needed. This is especially key for vector-transmitting species like mosquitoes, in which only females bite and transmit diseases. While several genetic and transgenic approaches have been developed that permit male-female separation for some species, separation based on sexual size dimorphism continue to be a useful technique in the laboratory and in small factory settings for elimination of females. In general, female mosquitoes of many species such as Aedes and Culex but also Anopheles quadrimaculatus and A. albimanus are larger than males in the pupae stage.
Vienna Scientific Instruments develops prototypes of size-based sex separator systems for the FAO/ IAEA Insect Pest Control Laboratories. The mechanical sex separator consists, for example, of an acrylic tube as main body in which a tray with pupae can be inserted. The constructed tray not only simplifies pupae insertion but also removes air bubbles. Several sieves of various sizes can be inserted and removed with a detachable handle. The sieves allow differently sized male and female to reach different compartments from where they can be removed separately. Other models are based on the classical larval-pupal separator (narrowing metal or glass plates) but with an convenient and efficient entering and washing mechanism and three or more levels of separation.