TIMING OF PUPATION OF INOPUS RUBRICEPS (MACQUART) (DIPTERA, STRATIOMYIDAE) IN SUGARCANE FIELDS

Larvae of sugarcane soldier fly, Inopus rubriceps, pupated during autu mn in sugarcane fields. Under conditions of moist soil and good cane g rowth, pupation occurred about 1 month later in northern and central Q ueensland than in southern Queensland and northern New South Wales, an d this was related to soil temperature. The midpoint of the pupation p eriod coincided with mean soil temperatures of 20-25 degrees C in each area. A laboratory experiment showed that pupation was inhibited at 2 5 degrees C and favoured by lower temperatures. The timing of pupation varied between years in one canefield in southern Queensland. Late pu pation in 1991 was associated with small average size of larvae in ear ly autumn and with dry soil conditions and poor cane growth. A high pr oportion of larvae failed to pupate before winter in this field in 199 1. In normal years this carry-over of larvae into winter was only abou t 10%. Male pupae were smaller than female pupae. Pupal weights were s imilar in each of the areas and years studied, but in some fields pupa l weights declined with time during the pupation period.