The Queensland fruit fly (Dacus [StrumetaJ tryoni) is the common pest species in the coastal areas and in certain other districts of this State and mainly infests summer fruits, particularly the later varieties. Citrus fruits, except grapefruit, are not generally infested to any extent although disfigurement, dropping of fruit and losses may occur following egg-laying and associated development of decay organisms.

The fly is rather wasp-like in general appearance and lays its eggs in punctures or " stings " made by the ovipositor of the female. Eggs are not laid in the blossoms but in the developing fruits which become susceptible in the few weeks prior to maturity and harvesting.

Hatching occurs in two to three days and the maggots burrow through the fruit tissue. The maggots mature in seven or more days, leave the fruit and enter the soil to form a smooth light-brown oval puparium. The adult fly develops within the puparium, bursts its way out and emerges from the soil. Adults may live for long periods and the fly normally overwinters in this form. A generation may occupy about live weeks and five or more overlapping generations may occur each year.

Infestation normally begins with the earlier ripening loquats, a lull occurs about November and activity ceases for the season with an attack on late hanging main crop citrus fruits and on early navels, blackberries and guavas.