Inclusion of an alien species in the host range of the Neotropical parasitoid Hymenoepimecis bicolor (Brullé, 1846) (Hymenoptera, Ichneumonidae)

Marcelo O Gonzaga,Diego G Pádua,Adilson Quero

doi:10.3897/jhr.89.76620

Marcelo O Gonzaga, Diego G Pádua + Show 1 more

Open Access

https://doi.org/10.3897/jhr.89.76620

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Abstract

In this study we report the first case of an introduced alien host spider species being parasitized and manipulated by an ichneumonid wasp. Hymenoepimecis bicolor, previously described parasitizing exclusively Trichonephila clavipes (Araneidae), was observed parasitizing the European species Cyrtophora citricola (Araneidae) in southeastern Brazil. The cocoon web built by the parasitized spider is composed of a reduced horizontal sheet, which maintains the radial structure. The reduced number of radii and spirals probably reduce the chances of insect interception by these modified structures. In addition, the density of supporting threads is apparently very different between normal and modified webs. The cocoon web spun by C. citricola lacks the protective barrier structure usually observed in cocoon webs spun by parasitized females of T. clavipes. Our observations are in agreement with several predictions of the ecdysteroid hypothesis and represent an interesting opportunity for further investigation of interactions between these parasitoids and their spider hosts.

Highlights

We located eight other webs of unparasitized individuals of C. citricola in a transect of 5 × 200 m from the site where we found the first cocoon web, on the same day
The general structure of the cocoon webs of C. citricola differs from those of normal webs, including the reduction of the fine meshed sheet of dry silk, which is always present in webs of unparasitized individuals (Figs 1, 2)
The observation reported here is, as far as we know, the first record of a recently introduced alien host being parasitized by a species of Hymenoepimecis (Eberhard and Gonzaga 2019)

Summary

Introduction

Hymenoepimecis Viereck, 1912 is a genus of parasitoid wasps included in the Polysphincta group of genera, members of which are usually referred to as ‘polysphinctines’ (Hymenoptera, Ichneumonidae, Pimplinae) (Matsumoto 2016). Most reports of the interactions between Hymenoepimecis and their hosts indicate that spiders change their web-building behaviors because of the action of late instar wasp larvae, possibly through the inoculation of the hormone ecdysone or some precursor of this hormone (see Kloss et al 2017; Eberhard and Gonzaga 2019). These changes result in modified cocoon webs with particular designs, and the survival of pupae of each parasitoid species may depend on specific designs obtained from their hosts.

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