Sugar-feeding by adult ichneumonoid and stephanoid wasps (Hymenoptera) in dry evergreen forest, Thailand

Many temperate parasitoid wasp species are known to consume sugars as adults. However, little is known about their adult nutritional ecology in the tropics. Here we present the results of sugar analyses of adult parasitoid wasps collected in dry evergreen forest in Thailand.

Sugars were detected using cold anthrone tests, and the results validated for a subsample using high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD). Sugars were detected in 90% of stephanids (n=218), 81% of ichneumonids (n=563), and 60% of braconids (n=1,665).

We examined whether the presence or absence of sugar and the amount detected were influenced by family (Braconidae, Ichneumonidae, Stephanidae), body size, sex, life history strategy (idiobiont, koinobiont), or weather (rainy vs drier months).

Both the incidence of sugar-feeding and the amount detected were strongly positively correlated with body size, and season. Larger individuals were significantly more likely to be sugar positive as well as individuals collected in the dry season. However, family (Braconidae vs Ichneumonidae) was also a significant factor for incidence of sugar-feeding.

Sugar-feeding prevalence was significantly associated with life history strategy in both families but in opposite directions: koinobiont ichneumonids were more likely to have fed on sugar, whereas koinobiont braconids were less likely. Sugar feeding by braconid wasps was significantly more likely during rainy months. When interactions between variables were taken into account, these relations also changed with weather and weather:size and weather:size:life history interactions being significant for ichneumonids, but for braconids the significant explanatory variables were size, life history and size:life history interaction.