Effects of dietary components on diet consumption, reproductive allocation and larval development of the boll weevil, Anthonomus grandis

Abstract

The effects of varying dietary nitrogen, lipid and sucrose on diet consumption, nutrient utilization and reproductive allocation were studied in the female boll weevil, Anthonomus grandis (Coleoptera:Curculionidae). Additionally, the role of dietary components on larval development was investigated. Artificial diets were employed containing cottonseed flour (CSF) as the amino acid nitrogen source, sucrose as the carbohydrate source and wheatgerm oil as the source of dietary lipid. The content of dietary nitrogen was the primary diet component that influenced fecundity. Egg production was optimal with a diet containing high nitrogen (10% CSF). Moderate nitrogen reduction (5% CSF) initially delayed the onset of egg production, but eventually, daily egg production equalled, then surpassed the rate for females fed the high N diet (10% CSF). This was achieved by increased diet consumption and increasing the percentage of the absorbed diet that is dedicated to egg formation. Drastic nitrogen reduction (2.5% CSF) resulted in both a delay and a reduction in daily egg production. Short days (10:14, L/D) and cool scotophase temperatures (27(DEGREES)C:15(DEGREES)C, L/D) accentuated the reduced rate of egg production by females fed the 2.5% CSF diet. Under this photoperiod and temperature regimen, egg production was depressed by 50% relative to females fed the 2.5% CSF diet under a long day (13:11, L/D) photoperiod at a constant temperature of 27(DEGREES)C. Females fed the 10% CSF diet containing 3- and 5-fold increases in sucrose maintained equal or greater rates of egg production compared to 10% CSF controls. A 3- to 4-fold increase in diet consumption was observed between days 2-6 post-eclosion by females fed the high carbohydrate diets. Larval development was dependent on the concentration of dietary nitrogen. The rate of larval development was reduced as dietary nitrogen was reduced. Neither lipid nor carbohydrate content of the diet affected development rate, weight at pupation or the duration of the pupal stage