A comparison of nectar- and honeydew sugars with respect to their utilization by the hymenopteran parasitoid Cotesia glomerata

Fourteen naturally occurring sugars were individually tested with respect t o their effect on Cotesia glomerata longevity. Parasitoids kept with soluti ons of either sucrose, glucose and fructose lived for > 30 days. This const itutes a factor 15 increase in life span in comparison to control individua ls kept with water only. Stachyose, mannose, melezitose, melibiose, maltose and erlose increased parasitoid longevity by a factor of 11.2-6.9. Solutio ns of galactose and trehalose had a marginal, but still significant effect. Lactose and raffinose did not raise parasitoid longevity, while rhamnose a ctually reduced parasitoid survival. In an additional experiment, the relat ionship between quantity of sugar consumption and longevity was established for all 14 sugars. To study the effect of an unsuitable sugar in sugar mix tures, a range of glucose:rhamnose mixtures was tested. Even at 20% of the sugar mixture rhamnose suppressed the nutritional benefit of the 80% glucos e. The nutritional suitability of the sugars shows a positive correlation w ith the previously reported gustatory response towards the individual sugar s. Patterns of sugar utilization are discussed with respect to hydrolytic e nzymes and carbohydrate biochemical characteristics. Our findings for C. gl omerata are compared to patterns of sugar utilization reported for other sp ecies. The comparison between C. glomerata and its host Pieris brassicae re veals that the parasitoid is capable of utilizing a range of sugars that ar e unsuitable to its herbivorous host. This specificity opens up opportuniti es to select food supplements for biological control programs that selectiv ely target the antagonist, without concurrently enhancing herbivore fitness . (C) 2001 Elsevier Science Ltd. All rights reserved.