Order:
Wings and wing pads absent. Eye spots sometimes visible, but compound eyes absent. Segmented legs absent, but sometimes fleshy prolegs present. Sometimes with distinct head, often without head or with head drawn deeply into thorax. Body flattened, cylindrical, or maggot-like.
Family:
Mandibles move against each other along a horizontal or oblique plane. Head complete, fully exposed, distinct from thorax, and usually without lengthwise incisions. Head capsule usually with pair of conspicuous fans. Prothorax with single proleg ventrally. Thoracic segments usually individually distinguishable. Posterior abdominal segments 5–8 swollen, with ballooned or bowling-pin appearance. Last abdominal segment ringed with several radiating rows of small hooks. Mature larvae usually 3–8 mm long, or greater.