Spilothyrateles illuminatorius (Gravenhorst, 1820)

Verheyde, Fons, Hoekstra, Paul, Libert, Pierre-Nicolas, Meijer, Hilco, Ketelaere, Augustijn De, Vandaudenard, Thibaud, Belgers, Dick & Brosens, Edwin, 1880, Two hundred and five ichneumonid wasps reported for the first time in Belgium and the Netherlands (Hymenoptera: Ichneumonidae), Belgian Journal of Entomology 122, pp. 1-142 : 75-77

Spilothyrateles illuminatorius (Gravenhorst, 1820) (Fig. 38 A–B)

Spilothyrateles is a smaller genus within Ichneumonini . In contrast to Ichneumon spp. first tergite and hypopygium are elongate and gastrocoeli are relatively small (HILPERT, 1992).

Spilothyrateles illuminatorius is sexually dimorphic. The females have tergites 2–3 red, while the third tergite has a black stripe basally. Other tergites are black, but the last two have a characteristic white stain (Fig. 38 A). This in combination with the yellowish scutellum and the reddish frontal orbits distinguishes the species from others. The males superficially resemble other black-yellow Ichneumon males. However, just like the females, there is a black stripe basally on the third tergite (which is yellow). The frontal orbits are also yellow and the flagellum is brownish. From a lateral view, their face is (strongly) convex, resembling Cratichneumon spp. Finally, the front and mid femora are stained black on the inner side, the hind tibiae are yellowish with a black ring apically and the hind coxae are completely black (Fig. 38 B).

This species has been vastly ignored or underreported in the past, which is partly due to the poor description in recent literature. The females are known to hibernate as adults, exclusively on grass tussocks and old stems from all kinds of vegetation. One report was made on the outside of a bee hotel, suggesting the plants and twigs deposited there housed at least one specimen. Next to these findings, S. illuminatorius appears to have a slight preference for open habitats, for example coastal dunes and limestone grasslands. The hosts are several common lepidopterans from the families Noctuidae and Notodontidae ( YU et al., 2012) .

First report for the Netherlands; confirmed in Belgium.

MATERIAL EXAMINED:

BELGIUM: • 1 ♂; Viroinval (NA); 50°04’41”N 4°36’00”E; 16/ix/2012; A. Moers leg.; field observation; F. Verheyde det. (ObsID: 71268995) . • 1 ♀; Oostende , Havengebied - Halvemaandijk (WVL); 51°14’14”N 2°55’31”E; 9/x/2014; W. Decock leg.; field observation; F. Verheyde det. (ObsID: 89068553) . • 1 ♂; Anderlecht , Begraafplaats (BR); 50°48’46”N 4°16’54”E; 19/vi/2016; M. Cuypers leg.; field observation; F. Verheyde det. (ObsID: 120155992) . • 1 ♀; Hermalle-sous-Argenteau (LG); 50°43’16”N 5°41’05”E; 28/vii/2017; L. Bronne leg.; field observation; F. Verheyde det. (ObsID: 142162534) . • 1 ♀; Geluveld , Polygoonbos (WVL); 50°51’25”N 2°59’34”E; 26/viii/2019; F. Verheyde leg.; coll. FV; field observation; F. Verheyde det. (ObsID: 178625844) […] .

THE NETHERLANDS: • 1 ♀; Helvoirt , Loonse en Drunense Duinen (NB); 51°39’15”N 5°12’10”E; 9/iii/2017; J. Bokelaar leg.; field observation; F. Verheyde det. (ObsID: 135222909) . • 1 ♀; Klein Valkenisse , Duinen en strand (ZL); 51°28’57”N 3°30’46”E; 11/iv/2017; A. van Gilst leg.; field observation; F. Verheyde det. (ObsID: 136739484) . • 1 ♀; Goirle , Regte Heide (NB); 51°30’32”N 5°01’31”E; 24/ix/2018; M. Verbeeten leg.; field observation; F. Verheyde det. (ObsID: 162847091) . • 1 ♀; Moerdijk , Industriegebied (NB); 51°41’02”N 4°35’19”E; 31/x/2018; N. Kroese leg.; field observation; F. Verheyde det. (ObsID: 165917670) . • 1 ♂; Zwolle , Vreugderijkerwaard (OR); 52°31’03”N 6°01’04”E; 22/vi/2019; R. & B. van Middelkoop leg.; field observation; F. Verheyde det. (ObsID: 178201075); Fig. 38 B […] .