Search

We examined gustatory responses of the larval parasitoid Microplitis croceipes to determine whether the adults discriminate among common sugars, including fructose, glucose, maltose and sucrose, found in plants. When given single sugar solutions of sucrose, glucose, fructose and maltose at concentrations of 0.008–2.0 mol l−1, the estimated concentrations at which 50% of wasps initiated feeding ranged between 0.054 and 0.085 mol l−1 for sucrose, glucose and fructose, which was significantly lower than for maltose. Wasps showed a strong decrease in feeding time for maltose or fructose following a brief exposure to other sugars, suggesting that wasps can distinguish maltose and fructose from the other sugars tested. The higher acceptance threshold and short feeding time in the case of maltose appears adaptive in light of the relatively poor nutritional quality of the sugar in the longevity trial. The pronounced feeding inhibition seen for fructose following exposure to other sugars is not linked with lower nutritional performance. This feeding inhibition was even seen in wasps that had fed on glucose at the lowest acceptance threshold (0.031 mol l−1) and persisted for 24 h. This study is the first to show feeding inhibition of otherwise phagostimulant sugars such as maltose and fructose after gustatory stimulation on other sugars.

We examined gustatory responses of the larval parasitoid Microplitis croceipes to determine whether the adults discriminate among common sugars, including fructose, glucose, maltose and sucrose, found in plants. When given single sugar solutions of sucrose, glucose, fructose and maltose at concentrations of 0.008–2.0 mol l−1, the estimated concentrations at which 50% of wasps initiated feeding ranged between 0.054 and 0.085 mol l−1 for sucrose, glucose and fructose, which was significantly lower than for maltose. Wasps showed a strong decrease in feeding time for maltose or fructose following a brief exposure to other sugars, suggesting that wasps can distinguish maltose and fructose from the other sugars tested. The higher acceptance threshold and short feeding time in the case of maltose appears adaptive in light of the relatively poor nutritional quality of the sugar in the longevity trial. The pronounced feeding inhibition seen for fructose following exposure to other sugars is not linked with lower nutritional performance. This feeding inhibition was even seen in wasps that had fed on glucose at the lowest acceptance threshold (0.031 mol l−1) and persisted for 24 h. This study is the first to show feeding inhibition of otherwise phagostimulant sugars such as maltose and fructose after gustatory stimulation on other sugars.

We investigated whether the age of field margins that had been established for conservation of northern bobwhite populations also enhance biological pest control in adjacent cotton fields. The impact of second year margins on the cotton crop did not significantly differ from first year margins with regard to pests or biological control. Analysis of the gut contents of M. autographae, suggested that this species is food-limited in the margins, whereas a single vetch species proved to be a good food source. This study shows that non-crop structures designed for a particular ecological function may be unsuitable for other ecological services. By making small adjustments in the vegetative com posit ion, we might be able to effectively stack multiple ecological functions and thereby optimize ecological benefits.

1. Vegetative buffers in agricultural landscapes can provide a range of important ecological services, including conservation of native flora and fauna, enhancement of biological pest control and reduction of agrochemical drift. Typically, studies addressing the impact of such vegetative elements focus on one particular benefit. We investigated whether the benefits of field margins that had been established for conservation of northern bobwhite quail Colinus virginianus populations extended to the enhancement of biological pest control in adjacent conservation tillage cotton fields. 2. Densities of a selection of insect species and the predation and parasitism rates of insect pest species were measured in first- and second-year field margins established for bobwhite quail as well as in an adjacent cotton crop. 3. Second-year field margins yielded higher densities of all species sampled, with the exception of staphylinids and cotton aphids. Despite this, thrips and their predator, Orius insidiosus, were the only species that were also more abundant in the adjacent cotton field. Tachinids and Trichogramma and Lygus species, appeared to prefer the field margin vegetation over the cotton. 4. Overall, the impact of second-year margins on the cotton crop did not significantly differ from first-year margins with regard to pest occurrence or biological control. 5. Analysis of the sugar content in Meteorus autographae, a generalist parasitoid of Lepidoptera larvae, suggested that this species is severely food-limited in the field margins established for bobwhite quail. 6. Synthesis and applications. This study shows that field margins designed to specifically benefit bobwhite quail may be unsuitable for providing other ecological services. By making small adjustments in the vegetative composition of these field margins, such as adding early season nectar-producing plants, it may be feasible to combine biodiversity and pest-control benefits and thereby optimize the overall ec

1. Vegetative buffers in agricultural landscapes can provide a range of important ecological services, including conservation of native flora and fauna, enhancement of biological pest control and reduction of agrochemical drift. Typically, studies addressing the impact of such vegetative elements focus on one particular benefit. We investigated whether the benefits of field margins that had been established for conservation of northern bobwhite quail Colinus virginianus populations extended to the enhancement of biological pest control in adjacent conservation tillage cotton fields. 2. Densities of a selection of insect species and the predation and parasitism rates of insect pest species were measured in first- and second-year field margins established for bobwhite quail as well as in an adjacent cotton crop. 3. Second-year field margins yielded higher densities of all species sampled, with the exception of staphylinids and cotton aphids. Despite this, thrips and their predator, Orius insidiosus, were the only species that were also more abundant in the adjacent cotton field. Tachinids and Trichogramma and Lygus species, appeared to prefer the field margin vegetation over the cotton. 4. Overall, the impact of second-year margins on the cotton crop did not significantly differ from first-year margins with regard to pest occurrence or biological control. 5. Analysis of the sugar content in Meteorus autographae, a generalist parasitoid of Lepidoptera larvae, suggested that this species is severely food-limited in the field margins established for bobwhite quail. 6. Synthesis and applications. This study shows that field margins designed to specifically benefit bobwhite quail may be unsuitable for providing other ecological services. By making small adjustments in the vegetative composition of these field margins, such as adding early season nectar-producing plants, it may be feasible to combine biodiversity and pest-control benefits and thereby optimize the overall ec