POPULATION AGE COMPOSITION AND FEMALE LONGEVITY OF THE ARBOVIRUS VECTOR CULEX ANNULIROSTRIS SKUSE NEAR ECHUCA, VICTORIA, IN THE MURRAY VALLEY OF SOUTHEASTERN AUSTRALIA 1979‐1985

Abstract

A population of Cx annulirostris in a state forest near Echuca, Vic, was sampled with a dry ice-baited encephalitis virus surveillance (EVS) trap from 1979 to 1985, generally on a fortnightly basis. These collections were combined for monthly samples which were dissected for parity and population age composition. The proportion parous varied between months and between years; for mid-summer (February) proportion parous ranged from 054 t o 083. There was no evidence that the population was autogenous. Monthly average duration of the gonotrophic cycle was estimated for October to May, and ranged from 4 days to 12 days. The probability of survival through one day in summer, taken from the proportion surviving from 1-parous to 2-parous, averaged 075 over 3 years. This average was higher (089) if calculated from the proportion parous. Females old enough t o transmit Murray Valley Encephalitis (MVE) virus were recorded from October to May, and represented up to 158% of the total collection in one season (1979-80).