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Revision of the World species of Xeris Costa (Hymenoptera: Siricidae)
CJAI 28 -- September 25, 2015
doi: 10.3752/cjai.2015.28
Henri Goulet1, Caroline Boudreault1 and Nathen M. Schiff2
4. Biology
4.1 Introduction

Not much has been published on the biology of Xeris species. The Asiatic X. malaisei (published as X. spectrum spectrum in Fukuda et al. 1997) from Japan is the only species with significant biological information. There is also some information on the biology of what is probably X. spectrum (Francke-Grossmann 1954), the more commonly captured species in Germany.

The most interesting feature of X. malaisei (Fukuda et al. 1997), and also X. caudatus (Schiff et al. 2012), is that females do not carry symbiotic fungus in their mycangia. The question is, therefore, what do larvae eat during their development? Females of most species of siricine Siricidae carry arthrospores of Amylostereum spp., one of the siricid host-specific basidiomycete fungi. During oviposition the fungus is deposited on each egg placed in the sap wood. The fungus produces an enzyme to decompose the wood cellulose or lignin, changing it into a form that can be assimilated by the larvae and making larval development possible. Fukuda et al. (1997) clearly showed that larvae of X. malaisei develop only if A. chailletii or A. areolatum are present at the oviposition site. Both species of fungi are equally accepted by Xeris larvae. Their observations confirm those of Francke-Grossmann (1954) on X. spectrum where females often deposit their eggs in trees already infested with Sirex and Urocerus spp. Moreover, the emergence holes of X. malaisei are in close proximity to those of other horntails (Fukuda et al. 1997). This suggests that females of Xeris are attracted by odors emitted by Amylostereum fungi inoculated by other fungus carrying horntails.

The emergence cycle of well-sampled species show interesting and distinct patterns. We have data from three species. X. spectrum has one emergence peak in late spring (Fig. C12.8), X. pallicoxae has a double emergence peak in late spring and early summer followed by a very small emergence in late September and early October (Fig. C11.9), and X. malaisei shows two clearly separated peaks of emergences, one in spring and one in summer (Fukuda et al. 1997) (Fig. C8.4). The spring oviposition cycle offers X. malaisei larvae a very viable fungus but more competition with other horntail larvae, whereas a summer oviposition cycle offers the Xeris larvae a less viable fungus with less competition from other horntail larvae (Fukuda et al. 1997).

Table of contents Abstract Introduction Materials and Methods Biology Hosts Parasitoids Morphology Key DNA References Citation Appendices PDFs