The northernmost record of Eriostethus rufus (Uchida, 1932) (Hymenoptera, Ichneumonidae) with an indication of new host, Trichonephila clavata (Koch, 1878) (Araneae, Araneidae) and its web manipulation

Keizo Takasuka

doi:10.37486/2675-1305.ec03015

Abstract

Eriostethus rufus (Uchida, 1932) is a polysphinctine ectoparasitoid of araneid spiders (Neoscona spp.) and is endemic to Japan. An individual was collected in Yamagata Prefecture (38º46' N), northern Japan, the northernmost record of the species and also the genus. Its identification was confirmed by morphology and by DNA barcoding. The cocoon was found in a large modified web, which is unique in that the web structure is shaped like an inverted triangle extending to over 50 cm with the cocoon hanging from an ill-defined part of the cocoon web without any organized structure surrounding the cocoon. The host spider of this individual appears to be Trichonephila clavata (Koch, 1878) (Araneidae, Nephilinae) based on several circumstantial evidences. The structure of the modified web suggests that the pre-existing web was partly reused, the orb web was completely removed, and sustaining threads of the barrier web would be newly moored to the substrates. This record means that E. rufus parasitises host spiders of two subfamilies, which is unusual for the group.

Highlights

Eriostethus rufus (Uchida, 1932) is a polysphinctine ectoparasitoid of araneid spiders (Neoscona spp.) and is endemic to Japan
Host records for Eriostethus are scarce, but two families have been recorded as host spiders so far; Araneidae by E. perkinsi (Baltazar, 1964) and E. rufus, and Theridiidae by E. minimus Gauld, 1984 (Iwata 1942; Korenko et al 2018a; Masumoto et al 2002; Matsumoto 2016)
Web manipulation, which is manifested by penultimate instar larvae behaviourally controlling a host spider, resulting in a “cocoon web” (Eberhard 2000), is known in Eriostethus perkinsi on Eriophora sp. (Korenko et al 2018a) and E. rufus on N. mellotteei (Matsumoto 2016)

Summary

Introduction

Eriostethus rufus (Uchida, 1932) is a polysphinctine ectoparasitoid of araneid spiders (Neoscona spp.) and is endemic to Japan. Host records for Eriostethus are scarce, but two families have been recorded as host spiders so far; Araneidae (orb web weavers) by E. perkinsi (Baltazar, 1964) and E. rufus, and Theridiidae (three-dimensional cobweb weavers) by E. minimus Gauld, 1984 (Iwata 1942; Korenko et al 2018a; Masumoto et al 2002; Matsumoto 2016).

Results

Conclusion