METHODS of estimating insect blood volume depend either on haemocyte counts before and after an injection of a measured volume of saline or on the dilution of amaranth dye by the haemolymph1. The latter method has been recommended for repeatable and consistent results with locusts2. Neither method, however, is likely to be practical for experiments with small insects, for example, the housefly, because the volume of liquid used for dilution (0.1–0.2 µl.) is too small to be administered with accuracy.