Order:
Larvae: Usually without lateral abdominal gills. If gills present, then 4 hooks clustered on segment 10. Thoracic legs each usually with 4 or 5 segments and with 1 or 2 claws; if without legs, head distinctly sclerotized and posterior body (thorax and abdomen) simple, without gills, hair brushes, suckers, or breathing tube. Eye spots usually present, but compound eyes absent.
Family:
Each mandible with 1 to 3 teeth along inner margin. Labrum and clypeus not separated by distinct suture. Antennae each 2- or 3-segmented. Head with simple-eyes in groups of 5. Legs each 3- or 4-segmented, with single claw; legs adapted for walking, sometimes small. Thoracic tergites clearly defined. Abdominal tergites without dorsal lobes. Abdomen usually 8-segmented. Body roughly cylindrical or spindle-shaped, not markedly thick. Head and legs visible in dorsal view.