Journal of Hymenoptera Research 31: 97–104, doi: 10.3897/JHR.31.4204
Notes on the biology of Seleucus cuneiformis Holmgren (Hymenoptera, Ichneumonidae, Ctenopelmatinae)
Cornelis van Achterberg 1, Ewald Altenhofer 2
1 Department of Terrestrial Zoology, Naturalis Biodiversity Center, Postbus 9517, 2300 RA Leiden, The Netherlands
2 Etzen 39, 3920 Gross Gerungs, Austria

Corresponding author: Cornelis van Achterberg (Cees.vanAchterberg@naturalis.nl)

Academic editor: G. Broad

received 28 October 2012 | accepted 21 January 2013 | Published 20 March 2013


(C) 2013 Cornelis van Achterberg. This is an open access article distributed under the terms of the Creative Commons Attribution License 3.0 (CC-BY), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.


For reference, use of the paginated PDF or printed version of this article is recommended.

Abstract

The biology of the monotypic genus Seleucus Holmgren, 1860 (Ichneumonidae: Ctenopelmatinae) is reported for the first time. Seleucus cuneiformis Holmgren, 1860, was reared from Blasticotoma filiceti Klug, 1834 (Hymenoptera: Blasticotomidae). Seleucus cuneiformis Holmgren is new to the fauna of Austria.

Keywords

Seleucus, Blasticotoma, biology, distribution

Introduction

The second author reared for the first time a species of Ichneumonidae from the fern sawfly Blasticotoma filiceti Klug, 1834 (Tenthredinoidea: Blasticotomidae) in Austria. Blasticotomidae form a small and rarely collected family of small wasps (6-9 mm) mainly restricted to the Palaearctic region and the border with the Oriental region (Taeger et al. 2010), with only one European species, Blasticotoma filiceti Klug, 1834. The family is considered to be one of the oldest extant families of Tenthredinoidea (Rasnitsyn 1988, 2002) and the blasticotomid lineage probably separated from the rest of Tenthredinoidea as early as 280 Ma (Ronquist et al. 2012). Blasticotoma filiceti Klug occurs both in the West and East Palaearctic regions (including the mountains of Taiwan). In Europe it is known from Austria, Denmark, England, Finland, Germany, Hungary, Ireland, Italy, Netherlands, Norway, Poland, Sweden, Ukraine, Wales, the European part of Russia, the Altai mountains and the Baikal region (Shcherbakov 2006, Knight and Howe 2006, Liston 2007, Bowdrey 2009, Prpic 2011). Blasticotoma filiceti has been known for the fauna of Austria from near Linz since 1973 (Schedl 1973) and the second find is reported here from the Austrian part of the Böhmerwald. The larvae of Blasticotoma filiceti live in the stems of ferns (especially of Athyrium filix-femina Roth) in a small chamber (or gall) and feed on the phloem fluids (“phloem-miner”; Shcherbakov 2006) and may produce foam on the outside of the gall. The larvae have a true ant trophobiosis (the only one known within the Hymenoptera); the Myrmica ants receive fluids through some holes connected to the stem gall of the larva (Shcherbakov 2006). The adult sawflies are only active in rainy weather in Europe during a short period (Liston 2007). If the ant trophobiosis is obligatory for the development of the sawfly larva it may limit the suitable places with Athyrium ferns and, connected with a short activity period of the adults at the end of May, it may explain why in Europe this family is probably very local.

The parasitoids reared by the second author belong to the aberrant genus Seleucus Holmgren, 1860. Townes (1971) classified Seleucus in the subfamily Phrudinae and Kolarov (1987) transferred it to the tribe Mesoleiini of the subfamily Ctenopelmatinae. Finally, Vikberg and Koponen (2000) transferred Seleucus to its own tribe, Seleucini, of the subfamily Ctenopelmatinae. The genus fits well in the subfamily Ctenopelmatinae according to a molecular phylogeny (Quicke et al. 2009) and its biology; nearly all Ctenopelmatinae (as far as is known) are endoparasitoids of Symphyta (Vikberg and Koponen 2000) and also some other genera of Ctenopelmatinae have the metasoma of the female compressed apically (e.g. Saotis Foerster, 1868). According to Quicke et al. (2009)Seleucus is sister group to the tribe Euryproctini of the Ctenopelmatinae. Seleucus cuneiformis Holmgren, 1860, is known from only a few countries in Europe (see below) and is new to the fauna of Austria. The second species included in Seleucus was Seleucus exareolatus Strobl, 1904, from Austria (Yu et al. 2012), but this species was excluded from Seleucus by Vikberg and Koponen (2000). Later it was synonymized with Microleptes rectangulus (Thomson, 1888) by Horstmann (2011) and belongs to the subfamily Microleptinae Townes, 1958. Shawiana foveolator (Thomson, 1895) (Braconidae: Exothecinae) and Tetrastichus rasnitsyni Kostjukov, 2001 (Eulophidae) are known parasitoids of Blasticotoma filiceti (Shcherbakov 2006) but have not so far been reared in Austria.

Material and methods

The larvae of Blasticotoma filiceti Klug were found in early August 2011 and 2012 in the Austrian part of the Böhmerwald (an area with mountain spruce forest on the border of Austria, Czech Republic and Slovakia with Plöckenstein (1378 m) as its highest point). Many spruce trees (Picea abies L.) died through storms and bark beetle infestation and all were removed in the Austrian part. The resulting open area was occupied by grass (Dechampsia sp.), Rubus idaeus L., Vaccinium myrtillus L. and some patches of a fern (Athyrium sp.; Fig. 1) with the central fronds damaged. The complete infested fronds of the fern were collected in a large plastic bag and stored vertically. Twice per day the larvae emerging from the stems of the fern leaves were removed and put into large glass jars half filled with fine earth covered with some pieces of old decaying wood or old stems of Verbascum sp. Some Sphagnum was added to maintain a higher and constant humidity in the jars. Jars with larvae or pupae were overwintered in a cellar in the second author’s garden in Gross Gerungs.

Figures 1–3.

Blasticotoma filiceti Klug, ♀, Austria, Plöckenstein, 1.viii.2012, but 3 15.v.2012. 1 Central fronds of Athyrium sp. damaged by larvae tunnelling in the stems 2 foam bubble produced by tunnelling larva 3 oviposition in unfolded fern frond. Photos: E. Altenhofer.

For identification of Seleucus Holmgren, see Townes (1971) and Vikberg and Koponen (2000). For references see Yu et al. (2012). The specimens are deposited in the Naturalis Biodiversity Center (RMNH) at Leiden and the Altenhofer collection (AC) at Gross Gerungs.

Biology

The Blasticotoma larvae were tunnelling in the stem (or rhachis) of the fern fronds, without causing external galls. The reported foam bubble (Shcherbakov 2006, Knight and Howe 2006) and faeces emerging from the hole in the stem are rarely seen (Fig. 2), probably it is consumed or destroyed by the observed visiting ants (Formica sp.), parasitoids (Ichneumonidae), flies (?Tachinidae), yellow jackets (Vespula sp.) and ladybird beetles (Coccinella septempunctata L.). The full-grown larvae of Blasticotoma filiceti Klug bore in decaying wood or in Verbascum-stems for pupation; they do not make a cocoon and need protection of a fairly solid medium in the absence of a cocoon. No adults, of either sawflies nor parasitoids, emerged from jars lacking wood or stems on top of the substrate. Adults of Blasticotoma filiceti emerged in May 2012 over a period of about two weeks and the females readily accepted fresh (still rolled-up) Athyrium fronds for oviposition (Fig. 3), but other ferns present in the garden were not accepted. Four weeks later the adults of Seleucus cuneiformis appeared over a period of two weeks. The specimens were kept alive for a few days, before they were killed for identification. The parasitoid females at first had a droplet-shaped metasoma like the males (Fig. 5), but during the first day the metasoma expanded into the very elongate shape typical of females (Fig. 4).

Figures 4–5.

Seleucus cuneiformis Holmgren, habitus lateral ♀ (4) and ♀ (5), Austria, Plöckenstein.

Seleucus cuneiformis Holmgren, 1860

http://species-id.net/wiki/Seleucus_cuneiformis

Figs 6–14
Material.

2 ♀ + 2 ♂ (RMNH) & 3 ♀ + 2 ♂ (AC), “Austria: Böhmerwald, Plöckenstein, 1200-1300 m, ex Blasticotoma filiceti on cf. Athyrium sp., coll[ected] 8.viii.2011, em[erged] 16 (1 ♂), 20 (1 ♀ + 1 ♂), 22 (1 ♂), 23 (2 ♀), 26 (1 ♀ + 1 ♂).vi.2012 & 1.vii.2012 (1 ♀), E. Altenhofer”.

Biology.

Parasitoid of larvae of Blasticotoma filiceti Klug, 1834 (Tenthredinoidea: Blasticotomidae). The sex ratio is nearly balanced as far as the low numbers allow a conclusion. Only one male appeared before the females emerged; the others emerged together with the females.

Distribution.

Palaearctic China (Henan), Czech Republic; Finland; Germany; Japan (Hokkaido); Korea; Poland; NW European Russia; Far East Russia; Sweden (Vikberg and Koponen 2000; Yu et al. 2012) and now Austria.

Notes.

The apex of the fore tibia has a more or less angulate lamella (Fig. 8, not a tooth as is supposed to be present in Ctenopelmatinae); the ovipositor sheath points upwards compared to the hypopygium (Fig. 9); the ovipositor has a dorsal notch (Vikberg and Koponen, 2000; which excludes it from the Phrudinae and corroborates its inclusion in the Ctenopelmatinae); the first metasomal tergite has a long petiole and the spiracles are halfway along the notum (Fig. 7); the pterostigma is triangular with vein r emerging medially (Fig. 6); the frons is coarsely punctate (Fig. 12); the metasoma of the female is 3.0–3.5 times longer than the mesosoma (Fig. 4); below the clypeus is a distinct space because the clypeus is distinctly removed from the mandibles (Figs 12, 13); the clypeus has an apical fringe of bristles (Fig. 13); and the hind tarsus is very slender (Fig. 14).

Figures 6–14.

Seleucus cuneiformis Holmgren, ♀ (except 11 = ♀), Austria, Plöckenstein. 6 Wings 7 first metasomal tergite dorsal 8 apex of fore tibia (arrow to angulate part of apical lamella) 9 ovipositor sheath lateral 10, 11 antenna 12 head frontal 13 head lateral 14 hind leg lateral.

Acknowledgements

We thank Kees Zwakhals (Arkel) for his critical remarks that helped us considerably to improve the paper. The authors are grateful to both reviewers (Gavin Broad and Andrew Bennett) for critical remarks and linguistic improvements.

References
Horstmann K (2011) Revisionen von Schlupfwespen-Arten XV (Hymenoptera: Ichneumonidae). Mitteilungen Münchener Entomologischen Gesellschaft 101: 5-13.
Bowdrey J (2009) Blasticotoma filiceti Klug new to Ireland. Sawfly Study Group Newsletter 4: 6.
Knight G, Howe M (2006) Blasticotoma filiceti Klug in North Wales. Sawfly Study Group Newsletter 1: 7-8.
Kolarov JA (1987) A new Ctenopelmatinae genus and species from Bulgaria (Hymenoptera, Ichneumonidae). Entomofauna 8 (6): 69-76.
Liston AD (2007) Zur Biologie und Vorkommen von Blasticotoma filiceti Klug, 1834 (Hymenoptera, Blasticotomidae) in Brandenburg und Berlin. Entomologische Nachrichten und Berichte (Dresden) 51: 95-99.
Quicke DLJ, Laurenne NM, Fitton MG, Broad GR (2009) A thousand and one wasps: a 28S rDNA and morphological phylogeny of the Ichneumonidae (Insecta: Hymenoptera) with an investigation into alignment parameter space and elision. Journal of Natural History 43(23-24)): 1305-1421. doi: 10.1080/00222930902807783
Rasnitsyn AP (1988) An outline of evolution of the hymenopterous insects (Order Vespida). Oriental Insects 22: 115-145.
Rasnitsyn AP (2002) Superorder Vespidea Laicharting, 1781. Order Hymenoptera Linné, 1758. In: Rasnitsyn AP, Quicke DLJ (Eds). History of insects. Dordrecht: 242-254. doi: 10.1007/0-306-47577-4
Ronquist F, Klopfstein S, Vilhelmsen L, Schulmeister S, Murray DL, Rasnitsyn AP (2012) A total-evidence approach to dating with fossils, applied to the early radiation of the Hymenoptera. Systematic Biology 61 (6): 973-999. doi: 10.1093/sysbio/sys058
Schedl W (1973) Erster Nachweis der Farnblattwespe Blasticotoma filiceti Klug, 1834 in Österreich (Hymenoptera, Blasticotomidae). Zeitschrift der Arbeitsgemeinschaft österreichischer Entomologen 25(3/4): 114–117.
Shcherbakov DE (2006) Fern sawfly larvae Blasticotoma filiceti Klug, 1834 (Hymenoptera: Blasticotomidae) are visited by ants: a new kind of trophobiosis. Russian Entomological Journal 15 (1): 67-72.
Taeger A, Blank SM, Liston A (2010) World catalog of Symphyta (Hymenoptera). Zootaxa 2580: 1-1064.
Townes HK (1971) The genera of the Ichneumonidae. Part 4. Memoirs of the American Entomological Institute 17: 1-372.
Vikberg V, Koponen M (2000) On the taxonomy of Seleucus Holmgren and the European species of Phrudinae (Hymenoptera: Ichneumonidae). Entomologica Fennica 11: 195-228.
Yu DSK, Achterberg C van, Horstmann K (2012) Taxapad 2012, Ichneumonoidea 2011. Database on flash-drive. www.taxapad.com , Ottawa, Ontario, Canada.