Species-Specific Chemical Signatures in Scale Insect Honeydew

Abstract

The quantity and chemical composition of honeydew produced by scale insects may influence wider community structure, but little is known about the detailed chemical composition of the honeydew found in forest ecosystems. We used gas chromatography-mass spectrometry to examine the amino acid and carbohydrate composition of honeydew from three New Zealand communities. Low molecular weight carbohydrates (mono-, di-, and trisaccharides) were derivatized using a modified trimethylsilyl (TMS) method, and amino and non-amino organic acids were derivatized using methylchloroformate (MCF). These recently developed derivatization methods allowed us to detect atypical compounds such as sugar alcohols, fatty acids, and non-amino organic acids, in addition to the more routinely studied compounds such as sugars and amino acids. Some compounds could not be identified and may be novel. Multivariate analysis showed that honeydew from each scale insect species had a distinctive amino acid and carbohydrate signature. We suggest these chemical signatures may influence the types of consumers that are attracted to different honeydews and may explain the characteristic communities associated with these honeydews.

Diverse Honeydew-Consuming Fungal Communities Associated with Scale Insects

“…For Ultracoelostoma spp. host plant influence on the composition of scale insect honeydew is minimal [6], perhaps explaining the apparent lack of influence of host tree species on the sooty mould community observed in this study. However, the narrow host preference of these scale insects prevents testing of this influence across phylogenetically distant host species: U. brittini attains large populations only on a few closely related beeches ( Nothofagus spp.)…”

“…For example, sooty mould fungi from seven genera are found in association with Nothofagus (beech) in New Zealand [5]. They are believed to derive their nutrients from coelostomidiid honeydew, which is a complex mixture of water-soluble carbohydrates such as sugars, sugar alcohols, water, free amino acids and proteins that varies among species [6]. This is believed to be due to differences in physiology of the scale insect species, rather than the influence of host tree or geographic location, as determined by previous work on honeydew compositional differences amongst these scale insect species [6].…”

“…They are believed to derive their nutrients from coelostomidiid honeydew, which is a complex mixture of water-soluble carbohydrates such as sugars, sugar alcohols, water, free amino acids and proteins that varies among species [6]. This is believed to be due to differences in physiology of the scale insect species, rather than the influence of host tree or geographic location, as determined by previous work on honeydew compositional differences amongst these scale insect species [6]. Similar differences have been reported for the amino acid composition in honeydews of physiologically different aphids [7].…”

Invasive Vespula Wasps Utilize Kairomones to Exploit Honeydew Produced by Sooty Scale Insects, Ultracoelostoma

“…While there have been other reports that describe the composition of the scale insect produced honeydew (Dhami et al 2011;Grant and Beggs 1989), this is the first study to describe the compounds that compose the scent of the honeydew of New Zealand's South Island beech forests. Aphid produced honeydew volatiles have been described elsewhere (Budenberg 1990;Carter and Dixon 1984;Ide et al 2007;Leroy et al 2012;Wäckers 2000).…”

“…Only the immature stages of the scale (1st -3rd female instars and 1st and 2nd male instars) actively feed on the phloem, and are hidden within a protective covering that is secreted by epidermal glands (Morales et al 1988). Like most phloem-feeding hemipterans, sooty beech scales produce a waste product called honeydew, which is high in carbohydrates (such as fructose, sucrose, and oligosaccharides) and low in protein (Dhami et al 2011;Grant and Beggs 1989). The amount of honeydew produced by sooty beech scales can be from 3800 to 4600 kg/ha/yr dry weight (Beggs et al 2005).…”