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:
head is not evident, but is reduced to some sclerotized rods inside the thorax; there are no segmented legs; the posterior end of the abdomen is blunt and smooth, without lobes, spines, or ridges.