This is the larva of a dipterous insect (Fig. 212) common in certain parts (especially the tropics) of America, from Canada to Patagonia. The insect (9-10 mm. long) lays a mass

of three or four hundred eggs on the surface of wounds, and in the ears and nasal fossæ (Fig. 214) of persons sleeping in the open air, especially of those having offensive discharges, which attract the fly. From these eggs the larvæ are hatched in a few hours. The larvæ (Fig. 213) are white, about three-quarters of an inch in length, and formed of twelve segments carrying circles of minute spirally arranged spines which give the