In most species, larvae are whitish grubs, roughly oval and bluntly-pointed at both ends. They have 15 segments and spiracles in each segment for breathing. They have no legs but move within the cell, helped by tubercles on their sides. They have short horns on the head, jaws for chewing food and an appendage on either side of the mouth tipped with a bristle. There is a gland under the mouth that secretes a viscous liquid which solidifies into the silk they use to produce a cocoon. The cocoon is semi-transparent and the pupa can be seen through it. Over the course of a few days, the larva undergoes metamorphosis into a winged adult. When ready to emerge, the adult splits its skin dorsally and climbs out of the exuviae and breaks out of the cell.