Honeydew composition and its effect on life‐history parameters of hyperparasitoids

Abstract

1. Diets that maximise life span often differ from diets that maximise reproduction. Animals have therefore evolved advanced foraging strategies to acquire optimal nutrition and maximise their fitness. The free‐living adult females of parasitoid wasps (Hymenoptera) need to balance their search for hosts to reproduce and for carbohydrate resources to feed. 2. Honeydew, excreted by phloem‐feeding insects, presents a widely available carbohydrate source in nature that can benefit natural enemies of honeydew‐producing insects. However, the effects of variation in honeydew on organisms in the fourth trophic level, such as hyperparasitoids, are not yet understood. 3. This study examined how five different honeydew types influence longevity and fecundity of four hyperparasitoid taxa. Asaphes spp. (Pteromalidae) and Dendrocerus spp. (Megaspilidae) are secondary parasitoids of aphid parasitoids and are thus associated with honeydew‐producing insects. Gelis agilis and Acrolyta nens (both Ichneumonidae) are secondary parasitoids of species that do not use honeydew‐producing hosts. 4. Most honeydew types had a positive or neutral effect on life span and fecundity of hyperparasitoids compared with controls without honeydew, although negative effects were also found for both aphid hyperparasitoids. Honeydew produced by aphids feeding on sweet pepper plants was most beneficial for all hyperparasitoid taxa, which can partially be explained by the high amount of honeydew, but also by the composition of dietary sugars in these honeydew types. 5. The findings of this study underline the value of aphid honeydew as a carbohydrate resource for fourth‐trophic‐level organisms, not only those associated with honeydew‐producing insects but also ‘interlopers’ without such a natural association.

Do plant volatiles confuse rather than guide foraging behavior of the aphid hyperparasitoid Dendrocerus aphidum?

“…Maranello) and winter wheat plants (Triticum aestivum var. Premio) were grown from seeds in a greenhouse using conditions and methods described in van Neerbos et al (2020). Pepper plants were grown individually in pots (1.45 L, 13 cm diameter) and used in experiments 5-6 weeks after sowing.…”

“…Moreover, after parasitized aphids turn into mummies and stop feeding on the plant, they no longer produce honeydew. Instead of directing hyperparasitoids to their host, attraction to honeydew may be driven by the substantial impact of this carbohydrate-rich food source on longevity and fecundity of aphid hyperparasitoids (van Neerbos et al 2020).…”

Analysis of sugars and amino acids in aphid honeydew by hydrophilic interaction liquid chromatography – Mass spectrometry

“…Honeydew composition is an important driver of ant-aphid interactions as well as interactions with predators and parasitoids [3 , 4] . A recent study reported how aphid honeydew composition affects longevity and fecundity on hyperparasitoid wasps, a fourth trophic level insect [5] . Total sugar content in honeydew can be characterized using colorimetric anthrone-sulfuric acid assays [6] though other analytical techniques provide more detailed information on the composition of specific sugars.…”

“… [8] Sugars: sorbitol, mannitol, trehalose, glucose, fructose, melibiose, sucrose, melezitose, raffinose, maltose HPLC with ECD 35 2.5 ppm van Neerbos et al. [5] Sugars: glucose, fructose, sucrose, trehalose, melibiose, maltose, isomaltose, maltulose, isomaltulose, melezitose, erlose, raffinose, 1-kestose, isomaltotriose, maltotriose, nidrose, stachyose HPLC with anion exchange column and pulse amperometric detection 25 Not reported Shaaban et al. [9 , 10] …”

Honeydew as a newly described route of insecticide exposure to beneficial insects

“…Growing evidence of important declines in insect populations has caused great concern among the scientific community (Biesmeijer et al, 2006;Dirzo et al, 2014;Goulson et al, 2008;Hallmann et al, 2017;Harvey et al, 2020;Potts et al, 2010). Studies carried out in a rainforest of Puerto Rico (Lister and Garcia, 2018) and European protected areas (Hallmann et al, 2017) showed insect biomass losses of more than 75% between 1989 and 2016.…”