Changes to web architecture of Leucauge volupis (Araneae: Tetragnathidae) induced by the parasitoid Hymenoepimecis jordanensis (Hymenoptera: Ichneumonidae)

Abstract

Some new cases of ectoparasitoid wasps from the Polysphincta genus-group manipulating the behaviour of host spiders have been described in recent years, indicating that the modification of normal web structure is the rule rather than an exception as the outcome of these interactions. In most cases, orb web diameter and the number of adhesive spirals are reduced, which decreases the probability of web damage from the interception of insects on the viscid threads during the development of the parasitoid within the cocoon. In this study, we describe a new interaction between the host spider Leucauge volupis and the recently described parasitoid Hymenoepimecis jordanensis. Web modifications induced by larvae in their last instar, in this case, are different to those described for two other Leucauge species attacked by Hymenoepimecis spp., L. argyra and L. roseosignatha. The cocoon webs constructed by the parasitized L. volupis are similar to those webs constructed by immature individuals, presenting a lower tangle, which may increase the stability of the web or offer additional physical protection for the cocoon. As in other previously described cases, sticky spirals are absent from cocoon webs. However, the photographs of webs constructed by spiders carrying second instar larvae indicated that the reduction in spirals begins before the construction of the cocoon web. These webs remain functional, being substantially modified only when the larvae reach the third instar. Variation among cocoon web designs of congeneric hosts attacked by distinct Hymenoepimecis species indicate that the substance used for host manipulation may vary in concentration and/or composition. Alternatively, distinct host responses may occur to the same substances.

Parasitism of Hymenoepimecis manauara Pádua & Oliveira (Hymenoptera: Ichneumonidae: Pimplinae) on Leucauge henryi Mello-Leitão (Araneae: Tetragnathidae) in Brazilian Amazonian

“…Probably the reduction in the number of radii and sticky spirals determine the reduction in the odds of insect interception, which would result in damages or even in web destruction (Gonzaga et al 2015). The attachment of the cocoon to this structure may also prevent the cocoon from falling on the ground.…”

“…He suggested that this modified web is very similar to build by spiders in juvenile stages of development. In the fourth case, Gonzaga et al 2015 collected adults and sub-adults of L. volupis (Keyserling. 1893) parasitized by H. jordanensis Loffredo & Penteado-Dias, 2009 in Minas Gerais state.…”

Proximate mechanism of behavioral manipulation of an orb-weaver spider host by a parasitoid wasp

“…Cocoon webs appear to be more resistant to rupture [18,20,21] and have fewer components (e.g., radii and sticky spirals in orb webs) that are utilized for prey interception and retention. Variations of this general pattern include the addition of barrier threads [22], shorter radii, doubled number of lines in each radius, construction of a reinforced frame [19], reinforcement of the retreat by addition of more threads [14] or a veil sheltering the cavity containing spider and larva [23]. These alterations are not a by-product of infection [20,21], but appear to be directly induced by the parasitoid larva.…”

Modification of Tetragnatha montana (Araneae, Tetragnathidae) web architecture induced by larva of the parasitoid Acrodactyla quadrisculpta (Hymenoptera, Ichneumonidae, Polysphincta genus-group)

“…A similar 2D cocoon web is built by the related species Leucauge roseosignata Mello-Leitão, 1943 manipulated by Hymenoepimecis japi Sobczak, Loffredo, Penteado-Dias and Gonzaga, 2009(Sobczak et al 2009. A similar 2D architecture of the cocoon web, but protected by the 3D structure of the tangle positioned below the hub, was recently described in the spider hosts Leucauge mariana (Keyserling, 1881) manipulated by Hymenoepimecis tedfordi Gauld, 1991 (Eberhard 2013) and Leucauge volupis (Keyserling, 1893) manipulated by Hymenoepimecis jordanensis Loffredo & Penteado-Dias, 2009 (Gonzaga et al 2014). In contrast, the larva of Eruga gutfreundi Gauld, 1991 induced the same host (L. mariana) to build a completely different three-dimensional cocoon web (hereafter 3D) (Eberhard 2013).…”