Modification of galls ofDiplolepis triforma(Hymenoptera: Cynipidae) by the parasitoidsEurytoma spongiosa(Hymenoptera: Eurytomidae) andGlyphomerus stigma(Hymenoptera: Torymidae)

Abstract

Stem galls induced by the cynipid Diplolepis triforma Shorthouse and Ritchie are frequently inhabited by several species of parasitic chalcids and ichneumonids that consume inducers or other parasitoids. Two of these parasitoids, the eurytomid Eurytoma spongiosa Bugbee and the torymid Glyphomerus stigma (Fabr.), consume gall tissues after they have consumed their insect hosts and are considered entomophytophagous. Both are koinobiont ectoparasitoids. Eurytoma spongiosa oviposits within gall chambers and attacks larvae of the inducer throughout the summer season, from the early growth phase of the galls until the galls mature. If the inducer is killed by E. spongiosa in early summer, nutritive gall cells degenerate into vacuolate parenchyma and are consumed. If the inducer is killed later in the summer, when galls begin to mature, nutritive cells persist in the chambers for about 1 week before degenerating. Glyphomerus stigma kills and consumes inducer larvae when galls are maturing. New nutritive cells appear under the influence of G. stigma and are then consumed. The ability of entomophytophagous chalcids to promote the formation of gall cells provides insight into the derivation of the gall-inducing guild.

Testing species limits of Eurytomidae (Hymenoptera) associated with galls induced by Diplolepis (Hymenoptera: Cynipidae) in Canada using an integrative approach

“…These impediments confound studies on host-parasitoid relationships within galls induced by Diplolepis ( e.g. , Shorthouse et al 2005; Leggo and Shorthouse 2006; Shorthouse 2010), and thus a novel approach is needed to delimit these morphologically similar species.…”

Sexually dimorphic gall structures correspond to differential phytohormone contents in male and female wasp larvae

“…However, at least in stem galls of the tephritid fly Eurosta solidaginis , patterns of phytohormone distribution indicate that the larva produces rather than accumulates phytohormones (Mapes & Davis, 2001a,b). The characteristic pattern of cell division and vascular‐tissue development in E. solidaginis galls (Beck, 1947; Blum, 1952), as well as in galls of many other insects (Rohfritsch, 1992; Brooks & Shorthouse, 1997; Dorchin et al , 2002; Leggo & Shorthouse, 2006; Sopow et al , 2003), also point to the insect as the source of phytohormones in galls.…”

Comparative morphology, biology and phylogeny of terminal-instar larvae of the European species of Toryminae (Hym., Chalcidoidea, Torymidae) parasitoids of gall wasps (Hym. Cynipidae)

“…Although we have not observed phytophagy in our samples, G. stigma has been reported as partially phytophagous, reverting to a diet of gall tissue once it host was consumed (Shorthouse, 1998). This behaviour is based on the potential ability to influence the development of new nutritive cells, which are then consumed (Leggo & Shorthouse, 2006). Fully grown larvae usually overwinter and adults emerge in summer when the new Diplolepis galls are developing.…”