Strongylogaster xanthocera (Stephens, 1835)

Macek, Jan, 2010, Taxonomy, distribution and biology of selected European Dinax, Strongylogaster and Taxonus species (Hymenoptera: Symphyta), Acta Entomologica Musei Nationalis Pragae 50 (1), pp. 253-271 : 260

Strongylogaster xanthocera (Stephens, 1835)

( Figs. 7 , 8 )

Material examined. CZECH REPUBLIC: BOHEMIA centr.: Milovice (5755), 5.v.2006, 2 spec. ; 25.v.2006, one larva on Pteridium aquilinum , 1 spec.; Těptín (6153), 8.v.2000, 1 spec., all J. Macek lgt. BOHEMIA bor.: České Švýcarsko NP: Vlčí potok brook (5052), 2.vi.2005, 1 spec., J. Macek lgt. ( MT) ; 22.v.2006, 1 spec., M. Trýzna lgt. ( MT) ; Mlýny hill (5152), 16.v.2007, 2 spec. ; Zadní Jetřichovice (5052), 6.vi.2007, 1 spec., M.Trýzna lgt .; Dolský mlýn mill (5152), 15.vi.2005, 3 spec., 22.v.2005, 1 spec. ; M. Trýzna lgt.; Suchá Bělá brook (5151), 15.vi.2005, 1 spec., M. Trýzna lgt .; Růžák NR (5152), 15.vi.2005, 2 spec. ; Srbská Kamenice (5152), 15.vi.2005, 1 spec. ; Ponova louka NR (5151), 19.vi.2006, 2 spec., 16.v.2007, 1 spec. ; Limberk hill (5052), 25.v.2007, 2 spec., M. Trýzna lgt ( MT). BOHEMIA occ.: Karlovy Vary distr., Nová Role env., Vlčí potok brook (5742), 2.vi.2005, 3 spec., J. Macek lgt. ( MT) ; Nová Role env., Černý potok brook (5742), 22.vi.2005, 2 spec., J. Macek lgt.( MT) ; all. J. Macek det. ( NMPC).

Adult. Notes on identification. Redescription was given by MUCHE (1969a). It differs from the similar S. multifasciata by feebly inflexed posterior margin of last sternum, the orange yellow antennae and bicoloured (black and white) hind femora in females and with more or less extensive black pattern on abdomen in males. Habitus as in Fig. 7 .

Larva. Redescription. The larva was first described by LORENZ & KRAUS (1957) and WELKE (1959). Body ground colour green with translucent dorsal blood vessel ( Fig. 8 ). Head orange yellow with variable dark pattern varying according to the stage of development: young instars with head orange yellow without dark pattern, older instars with variable pattern consisting of two parietal spots (as in S. multifasciata ), last instar with dark upper half of head.

Notes on identification. The last instar larvae differ from the similar S. multifasciata by the black upper half of the head. The larvae also appear earlier (May to June).

Bionomics. Univoltine. Flight period from late April to early June; larval period from May to June. Host plants: Dryopteris (= Aspidium ), Polystichum (Dryopteridaeceae) , Athyrium (Woodsiaceae) and Pteridium aquilinum (Dennstaedtiaceae) ( TAEGER et al. 1998). I collected the larvae exclusively on P. aquilinum .

Distribution. Palaearctic Region (central and northern Europe, Siberia, China, Japan) ( NAITO 1996). Scattered occurrence in the Czech Republic from uplands to highlands.

Comments. Both S. xanthocera and S. multifasciata are closely related and frequently occur at the same localities but have clearly separate flight periods. Strongylogaster xanthocera is a vernal species with the flight period from the end April to the end of the May, while S. multifasciata is mostly a summer species flying from early June to mid July, with partial overlap in late May and early June. The larvae of S. xanthocera feed on the bursting fronds of Pteridium and are grown up by early June, when the first instar of S. multifasciata appears. The larval period of S. multifasciata extends from June to early August before the ripening of the fern sori of Pteridium . Eonymphs of both species bore into bark for hibernation ( WELKE 1959) and in captivity they also accept dry rotten wood (my observation).

Figures

Figs. 2–7. Strongylogaster Dahlbom, 1835, adults: 2 – S. macula (Klug, 1817); 3 – S. baikalensis Naito, 1990; 4 – S. mixta (Klug, 1817); 5 – S. filicis (Klug, 1817); 6 – S. multifasciata (Geoffroy, 1785); 7 – S. xanthocera (Stephens, 1835). Scale: 10 mm.

Figs. 8–12. Strongylogaster Dahlbom, 1835, larvae: 8 – S. xanthocera (Stephens, 1835): a – immature instar (dorsal view); b – last instar (lateral view); c – last instar (laterodorsal view). 9 – S. multifasciata (Geoffroy, 1785): a – last instar (laterodorsal view); b – last instar (dorsal view). 10 – S. macula (Klug, 1817): last instar (laterodorsal view). 11 – S. baikalensis Naito, 1990: last instar (laterodorsal view). 12 – S. mixta (Klug, 1817): a – immature instar (laterodorsal view); b – last instar (lateral view); c – last instar (lateral view). Scale for last instar larva: 10 mm.