Key Characters of Adults

• Adults have one pair of membranous wings
• Hindwings of adults have been modified into halteres

Key Characters of Larvae

• Many do not have distinct heads (maggots) but some species do have distinct or reduced heads
• Segmented legs are absent on thorax
• Sometimes fleshy prolegs or other appendages are present on the first thoracic segment and/or last abdominal segment