The larch sawfly, Pristiphora erichsonii (Htg.), overwinters in a cocoon in the ground and has an adult emergence period that may last two months. Ecological studies of this insect require information on the number of adults emerging and the seasonal pattern of emergence. Several types of open-bottomed screen emergence cages without traps were tested but the insects caught in such cages were difficult to remove. Also, many of the adults were lost in the vegetation unless the cages were visited more frequently than was practicable. The trap described here, attached to a screen cage, eliminates the objections given above and could be of use to persons interested in insects which emerge from the soil.