Soft-bodied holometabolous insects with wingspans ranging from about 3mm to more than 100mm. Wings are membranous, usually with a dense network of cross-veins that gives the order its name: "nerve-winged". The veins usually fork prominently at the wing margins. Flight is weak in most species and the wings are generally held roofwise over the body at rest. Antennae usually thread-like. Compound eyes large, sometimes accompanied by 3 ocelli. Tarsi 5-segmented.