Semiochemical and physical stimuli involved in host recognition by Telenomus podisi (Hymenoptera: Scelionidae) toward Euschistus heros (Heteroptera: Pentatomidae)

Abstract

SummaryThe egg parasitoid, Telenomus podisi, was shown to recognize its host, Euschistus heros, through both chemical and physical cues. These were determined in short‐range bioassays. The cues comprised fertile and infertile host eggs, egg extracts, crude extracts of adult males and females and successive dilutions of the synthetic racemic mixture of methyl 2,6,10‐trimethyltridecanoate, a male‐produced pheromone of E. heros.Some of the treatments used induced a selection process in T. podisi, through host recognition behaviour, indicating a consistent response of this species to E. heros. The possibility that some of these compounds could be exploited as long‐range kairomones, by T. podisi, is discussed.Using GC analysis, an unidentified compound (Rt 24.8 min), possibly from the egg adhesive material, was detected from E. heros egg extracts. Its retention time compared to the methyl 2,6,10‐trimethyltridecanoate showed a lower volatility, suggesting that the egg adhesive may act as a short‐range kairomone.Physical cues appeared to be an important component in the host selection process by T. podisi. The parasitoid discriminated infertile eggs which are differently shaped and smaller than fertile eggs.

Sensory response of the egg parasitoid Telenomus podisi to stimuli from the bug Euschistus heros

“…This confirms previous assumption that this compound is used by the parasitoids to locate the host (Borges et al, 1999). There was no significant response among the other components of the sex pheromone: methyl 2,6,10-trimethyldodecanoate and 2,4 decadienoate and the male insects (Figure 2 B and C).…”

“…Egg masses alone caused little attraction in the parasitoid, but their combination with other stimuli increased the stimulation. The absence of orientation toward egg masses in arenas confirms previous reports that chemical cues from scelionid host eggs are nonvolatile and are used to recognize the host at short distances (<1 mm) Borges et al, 1999).…”

“…At least three sources of kairomones from E. heros have been found by Borges et al (1999Borges et al ( , 2003. In the laboratory, the influence of male sex pheromone on the searching behavior of the parasitoid has been reported (Borges et al, 1999).…”

“…Tactile cues are also used by the parasitoid, since it is able to distinguish between fertile and infertile host eggs, which are different in shape and size (Borges et al, 1999). Recently, it was demonstrated that this parasitoid recognizes specifically traces left on the substrate by the walking of E. heros females, and then searches intensively the area of the footprints, apparently looking for the host egg (Borges et al, 2003).…”

Egg parasitoid wasps as natural enemies of the neotropical stink bug Dichelops melacanthus

“…The selective response toward a specific host (E. heros) for three of the five species evaluated could suggest that these parasitoids use cues from host egg masses to identify those that would maximize their reproductive success. These cues could be related to physical (color, size, number and disposition of eggs, chorion thickness, corion ornamentation) and chemical (semiochemical) characteristics of the egg masses (Bin et al, 1993;Borges et al, 1999).…”