Food‐dependent regurgitate effectiveness in the defence of grasshoppers against ants: the case of bracken‐fed Abracris flavolineata (Orthoptera: Acrididae)

Abstract

The deterrence of a grasshopper, Abracris flavolineata, regurgitate against the fire ant, Solenopsis geminata, depends on diet. The ant deterrence of oral discharges of bracken-fed insects is greater than for those feeding on lettuce. A water extract of Pteridium caudatum fronds is also more potent in deterring the ants than a lettuce extract. A positive correlation between the content of phenolics in the regurgitate and deterrence is observed and bracken-derived oral fluids contain a 4.6-fold higher content of phenolics than lettuce-derived material. Nevertheless, no statistical difference is observed in condensed tannins content. The rate of transformation of bracken phenolics in the digestive tract of A. flavolineata proceeds quickly because, after only 48 h of discontinuing the diet, 53% of phenolics and 94% of tannins relative to the total present in the fronds are no longer in the ejected digestive fluid. It is suggested that this reduction may be a mechanism by which one fraction of the phenolics is metabolized or excreted and the other is used as defence via the oral secretion. The powerful deterrence index of bracken water extract indicates that other active secondary metabolites may also be present.

Armed Rollers: Does Nestling’s Vomit Function as a Defence against Predators?

“…Therefore, we expected to find a tritrophic effect of plant secondary compounds, from plant to insects and then to rollers. In agreement with our expectation, we found that all vomit samples contained hydroxycinnamic and hydroxybenzoic acids, that are phenolic acids usually found in leaves of many Gramineae and cell walls of most higher plants [18], [28], [41] and that deter insect feeding [29], [42]. Furthermore, some samples also contained traces of psoralen that is a furacoumarin produced by a wide variety of plants in response to pathogens and/or herbivore attacks [17].…”

“…These armed insects, hunted by adult rollers to feed their offspring, would be the putative source of phenolic acids contained in the vomit of roller. Previous work has demonstrated that oral secretion of different grasshopper species can deter predators [16]–[18], [31]. Here, for the first time, we show the deterrent effect of the oral secretion of a vertebrate, the avoidance of the oral secretion of nestling rollers by domestic dogs.…”

“…The defensive role of the expelled fluid has been attributed primarily to ingested plant secondary compounds [16]–[18]. Grasshoppers are the main prey that rollers hunt to feed their nestlings ([19], see below.…”

Disulfooxy fatty acids from the American bird grasshopper Schistocerca americana , elicitors of plant volatiles

“…Additionally, they may also be an important part of chemical defense, because grasshoppers regurgitate copious amounts of frothy secretions as a defense against attack. Indeed, investigations (36)(37)(38) have shown that both compounds from host plants and insect produced water-soluble components of the regurgitant have deterrent activity (36). Although the deterrent effect of caeliferins remains to be tested, it is probable that the emulsifying properties are important in aiding the water-based regurgitant to carry lipophillic toxic compounds.…”

Insects had it first: surfactants as a defence against predators

“…Enteric discharges from herbivores contain recently consumed plant material mixed with digestive and salivary secretions (Ortego et al 1997), but their mode of defence has been attributed primarily to ingested plant secondary compounds (e.g. Sword 2001;Calcagno et al 2004). Thus, defence seems to depend strongly on a herbivore's food plant.…”