The disclosure relates to a detection device for detecting movement of a live insect located within a seed or grain. The device may include a light source with a masking arrangement to block stray light. It may also include a detection region sized to contain at least one seed. Finally, the device may include a detection instrument able to detect changes in light from the light source caused by movement of an insect within the seed. The disclosure also relates to a method of detecting an insect in a seed. First, one may pass light through the seed. Then one may detect light passed through the seed and, based on the light passed through the seed, determine whether or not an insect within the seed is moving.