Typically you would measure the thermal hysteresis activity in the insect‘s hemolymph during freezing/thawing, using a nanolitre osmometer (e.g. Otago Osmometer). If I recall, you can also narrow down the type of antifreeze based on the shape of ice crystals you see in the hemolymph droplet. See a method here: Braslavsky I, Drori R. LabVIEW-operated novel Nanoliter Osmometer for ice binding protein investigations. J Vis Exp. 2013;4:e4189.