Relative Effects of Floral Resources on the Hyperparasitoid Phaenoglyphis villosa Hartig (Hymenoptera: Charipidae)

Altering biodiversity can influence higher trophic levels, which may in turn change their effects on food-web structure and ecosystem functioning. In this study, resource subsidies in form of added selected floral resources were evaluated in the laboratory to assess their effect on the longevity and potential fecundity of the fourthtrophic- level parasitoid, Phaenoglyphis villosa Hartig (Hymenoptera: Charipidae), which parasitises aphid primary parasitoids. When it was exposed to flowering buckwheat (Fagopyrum esculentum Moench cv. Katowase) or coriander (Coriandrum sativum L. cv. Slowbolt), P. villosa lived seven to ten times longer than it did when provided with water only and five times longer with phacelia (Phacelia tanacetifolia Bentham cv. Balo) or sweet alyssum (Lobularia maritima L. cv. Carpet of Snow). All flower species significantly increased P. villosa egg load. The hyperparasitoid females exposed to buckwheat and phacelia had higher potential fecundity compared to alyssum and control, whereas alyssum had more potential fecundity compared to control. Potential fecundity was at its maximum 48, 72 and 96 hours. On the other hand, it was at its minimum six hours after exposure to different treatments. These results indicate that floral resources deployed in conservation biocontrol should also be screened for their effects on the fourth trophic level. Modelling or field-cage experiments could be useful in elucidating the possible population and community consequences of deploying floral resources in agro-ecosystems to enhance biological control effectiveness.