Unlike in most biting Diptera, development of sand flies takes place in terrestrial rather than aquatic microhabitats. Although there have been relatively few successful attempts to identify breeding sites in nature, eggs are laid in soil rich in organic matter and the larvae pass through four instars before pupation and adult emergence. The difficulty of finding breeding sites is an important constraint on vector control measures available to leishmaniasis control programmes, application of larvicides not being a practical alternative.
The eggs are elongated oval-shaped, pale at first and darkening on exposure to air with a single black “eye spot”. The larvae emerge through a J-shaped fissure and are legless and whitish with a dark head capsule. Those of the first instar can be distinguished by the presence of two caudal bristles, all subsequent instars bearing four. Fourth instar larvae also have a prominent sclerite on the dorsum of the penultimate segment. The pupae are golden brown and are affixed to the surface of the substrate in which they developed by the final larval exuvium. Shortly before emergence the wings and eyes turn black. Male sand flies emerge about 24 h before females, allowing their external genitalia time to rotate 180° to the correct position for mating before females have emerged. Although there have been no studies of sand fly development time in nature, the time from oviposition to adult emergence at ambient temperature is around 4-6 weeks. Some Palaearctic species diapause as larvae.