Do acoustic cues mediate host finding by Syngaster lepidus (Hymenoptera: Braconidae)?

Abstract

Syngaster lepidus Brullé is a braconid solitary ectoparasitoid that attacks the larvae of the cerambycid beetles Phoracantha semipunctata and Phoracantha recurva. The beetle larvae are concealed under the bark of their Eucalyptus host trees feeding at the interface of the inner bark and the wood. Ovipositing female parasitoids search the bark surface and must first locate a host larva accurately, drill through as much as 1 cm of the bark in order to paralyze the larva beneath, and lay a single egg on the paralyzed larva. Female wasps were provided with logs infested with host larvae, in which the positions of the host larvae had been determined by X-ray imaging. The sequence of behaviors following the landing of a female wasp on an infested log was recorded on videotape and subsequently analyzed to provide a detailed description of the processes of host location and oviposition. Female wasps searched significantly more on log sections with active host larvae than inactive larvae. They also turned toward and moved in the direction of active larvae in response to sounds produced by feeding. While searching for hosts, female wasps stand on the log surface and walk towards the location of the larvae; while it is possible that they perceive both airborne sound and associated surface vibration, the vibration signals are probably more important in indicating direction and possibly distance to the host.

Impact of braconid wasps on larval performance of longhorned borer Coptocercus rubripes Boisduval (Coleoptera: Cerambycidae) in Eucalyptus forest of southwestern Australia

“…This inability to regulate high larval densities was also exhibited by the same braconid wasps in a previous study attacking P. semipunctata in E. globulus Labillardière and E. obliqua L'Héritier logs in eastern Australia (Hanks et al 2001). This response appears to depend on factors altering wasp effectiveness in finding larval hosts which may include use of volatiles to locate borer infested hosts (Johnson et al 2016), acoustic cues and audible mechanisms suggested to be used by wasps to find P. semipunctata larvae feeding on the phloem/sapwood (Joyce et al 2011), surface vibrations from borer larvae feeding (Godfray 1994) as was suggested to be used by these braconid wasps when attacking P. semipunctata (Hanks et al 2001), and intensive searching by other braconid wasps (Richerson & Borden 1972). Also, the increased choice of borer infested hosts, combined with the habit of these wasps to land on logs arbitrarily, rather than to remain in one place (Driessen & Bernstein 1999), may have meant that the braconid wasps were likely dispersing throughout the clearfell site and had moved away from host logs with high neonate densities, rather than increasing their chances of finding more individuals among a few logs.…”

“…2016), acoustic cues and audible mechanisms suggested to be used by wasps to find P. semipunctata larvae feeding on the phloem/sapwood (Joyce et al . 2011), surface vibrations from borer larvae feeding (Godfray 1994) as was suggested to be used by these braconid wasps when attacking P. semipunctata (Hanks et al . 2001), and intensive searching by other braconid wasps (Richerson & Borden 1972).…”

“…throughout Eucalyptus forests of eastern Australia (Austin et al 1994;Paine et al 2000;Hanks et al 2001). They are solitary idiobiont braconid wasps that lay a single egg in the borer larva and immobilise their prey following envenomation Joyce et al 2011). During an attack on P. semipunctata larvae developing in fallen timber within natural Eucalyptus forests of eastern Australia, the ovipositor length of the braconid wasp species partitioned their effectiveness depending on bark thickness and size of borer larvae (Hanks et al 2001).…”

“…2001; Joyce et al . 2011). During an attack on P. semipunctata larvae developing in fallen timber within natural Eucalyptus forests of eastern Australia, the ovipositor length of the braconid wasp species partitioned their effectiveness depending on bark thickness and size of borer larvae (Hanks et al .…”

Host specificity in the host-seeking larva of the dipteran parasitoidMallophora ruficaudaand the influence of age on parasitism decisions

“…The intense selection pressure on parasitoids to locate hosts is well illustrated by the variety of cues and strategies used in host searching (Wang et al , 2010; Joyce et al , 2011; Benelli et al , 2013 b , c ; Colazza et al , 2013; Uefune et al , 2013). The stimuli sources used by parasitoids may be direct, as the host itself, or indirect, as the microhabitat of the host or a cue associated with its activity (Vet & Dicke, 1992; Steidle & van Loon, 2003; Colazza et al , 2013; Uefune et al , 2013).…”