Tracing food source use by nectarivorous insects

F.L. Wäckers

Netherlands Institute of Ecology (NIOO-KNAW), Heteren, The Netherlands

Many insects depend on exogenous sugar sources, such as nectar and honeydew, as a source of energy. The availability of sugar sources can have a strong impact on spatial and temporal dynamics of nectarivorous insects. Whereas sugar feeding has been recognized as an important element in understanding plant-pollinator, plant-herbivore, and plant-carnivore interactions, we know relatively little about the sugar sources utilized by the latter two insect categories. Here we describe two methods that can be applied to study sugar feeding in insects under field conditions. While our research has primarily focused on parasitic wasps, the methods can also be applied to other nectarivorous arthropods.

As a first method, we investigated whether parasitoids could be durably marked through feeding on sucrose solution spiked with strontium or rubidium, or through feeding on extrafloral nectar from Vicia faba soil-drenched with aqueous trace elements.

As a second method, we have developed HPLC sugar analysis to study the sugar profile of the parasitoids Cotesia glomerata and Microplitis mediator. We describe the overall sugar level and the ratio of glucose to fructose as two parameters that in combination unambiguously characterize an individual’s nutritional state and feeding history. In addition to revealing past feeding events, HPLC analysis may also provide information about the type of sugar source consumed.

Paper presented at Measuring Behavior 2005 , 5^th International Conference on Methods and Techniques in Behavioral Research, 30 August - 2 September 2005, Wageningen, The Netherlands.

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