Apparatus 10 for sorting arthropod especially mosquitoes larvae and pupae on the basis of size and/or sex (determined by size), comprises a frame with four rotatably connected bars 12. This quadrilateral arrangement allows the frame to have its shaped altered so that the angle in the corner of the frame changes whilst the bars forming opposing sides remain parallel. A number of intermediate bars 14 are also provided, extending between opposing sides of the frame these are spaced apart by a gap of 1mm when the corner of the frames are positioned at 90 degrees. Insect larvae and pupae may be inserted into a chamber with one side formed by the grid of bars and inserted into water to separate the different forms. As the frame angle extends beyond 90 degrees, the space between bars 14 decreases accordingly (see Fig 5).
