The onion fly has an ash-grey body and resembles a housefly.
The male has a longitudinal stripe on the abdomen which is lacking in the female.
The legs are black, the wings transparent, and the compound eyes brown.
The eggs are white and elongated and are laid in groups on the shoots, leaves, and bulbs of host plants and on the ground nearby.
The larvae are white and cylindrical and hatch in 3 to 8 days.
Each batch of larvae tends to keep together and collectively create large cavities in bulbs.
More than 50 maggots may feed on one bulb, sometimes originating from eggs laid by several females.
The larvae moult three times, feed for about 20 days, and grow to about 1.0 cm long.
The pupa is brown, ringed, and ovoid and measures 7 mm (0.28 in) long.
Pupation occurs in the ground with the pupal phase from the spring generation lasting two or three weeks.
Late-generation pupae overwinter in the soil.
The onion fly has an ash-grey body and resembles a housefly. The male has a longitudinal stripe on the abdomen which is lacking in the female. The legs are black, the wings transparent, and the compound eyes brown. The eggs are white and elongated and are laid in groups on the shoots, leaves, and bulbs of host plants and on the ground nearby. The larvae are white and cylindrical and hatch in 3 to 8 days. Each batch of larvae tends to keep together and collectively create large cavities in bulbs. More than 50 maggots may feed on one bulb, sometimes originating from eggs laid by several females. The larvae moult three times, feed for about 20 days, and grow to about 1.0 cm long. The pupa is brown, ringed, and ovoid and measures 7 mm (0.28 in) long. Pupation occurs in the ground with the pupal phase from the spring generation lasting two or three weeks. Late-generation pupae overwinter in the soil.
Delia antiqua