Gustatory response by the hymenopteran parasitoid Cotesia glomerata to a range of nectar and honeydew sugars

The feeding response of food-deprived Cotesia glomerata to solutions of 14 naturally occurring sugars was determined. Glucose, fructose, sucrose, malt ose, erlose, melezitose, trehalose, and stachyose all elicited a feeding re sponse. The sugars differed, however with respect to the lowest concentrati on at which they were accepted (acceptance threshold). The parasitoids show ed no feeding response when presented with 2 M solutions of galactose, mann ose, rhamnose, lactose, raffinose, and melibiose. Sugars from the latter gr oup did not show a deterrent effect when offered to water-deprived parasito ids. When mannose, rhamnose, melibiose, or raffinose were combined with low molar solutions of either fructose or sucrose, sucrose acceptance was affe cted by mannose and raffinose, whereas no negative interactions were found in mixtures with fructose. Compared to acceptance thresholds reported in ot her insect systems, the responses of C. glomerata differ considerably with respect to both the range of saccharides accepted as well as the acceptance thresholds. The novel finding that the parasitoid accepts a number of suga rs that fail to elicit a feeding response in its herbivorous hosts is of pa rticular interest to the use of (selective) food supplements in biological control programs.