Birka cinereipes (Klug, 1816)

Macek, Jan, 2013, Descriptions of larvae of Birka annulitarsis and B. cinereipes (Hymenoptera: Symphyta: Tenthredinidae), Acta Entomologica Musei Nationalis Pragae 53 (2), pp. 815-819 : 818-819

Birka cinereipes (Klug, 1816)

( Fig. 2 )

Material examined. CZECH REPUBLIC: BOHEMIA CENTR.: Český kras PLA, Srbsko (6050), Karlštejn NNR, 13.ix.2008, 28 larvae on Myosotis palustris , 2 females emerged 25.iv.2009 ; Blaník PLA, Částrovické rybníky NR (6355), 27.vii.2010, 4 larvae on Myosotis palustris ; all J. Macek lgt. ( NMPC) .

Redescription of the last feeding instar larva. Body length 9–12 mm. Head black, clypeus and labrum brown, whole head covered with scattered fine homogeneous pubescence; clypeus with six setae, labrum with four setae; mandibles with two setae, stipes and palpifer with two setae; second segment of maxillary palps with one small seta; praementum with two setae, second segment of labial palp with one short seta; body in upper part black grey, in lower part yellowish grey; cuticle granulose, spiracles black; prothorax with a pair of enlarged dorsal and subspiracular lobes and wart-like suprapedal prominence; mesothorax with a pair of short wart-like dorsal projections and wart-like lateral projection; trochanter as long as femur covered with scattered hair-like setae, tibia as long as tarsus, covered with several scattered setae; body setae, excluding suranal and subanal lobes very short, cylindrical; third abdominal segment with seven annulets; annulets two and four with a pair of prominent wart-like dorsal protuberances with two setae; second annulet with two, fourth annulet with one, and third annulet in lower part with one, pale swellings with one or two setae; first postspiracular lobe with one, second postspiracular lobe with two or three setae; prominent subspiracular and suprapedal lobes with six to eight setae; ninth abdominal segment with transverse ridge with four lobes with two setae; suranal lobe with dense long hair-like setae on posterior half erected from black tiny conical warts; basal interior parts of prolegs with scattered conical and hair-like setae.

Notes on identification. The larvae of Birka cinereipes differ from the similar larvae of B. annulitarsis in the second and fourth annulet of the abdominal segments with wart-like protuberances and quadrilobed transverse ridge on the ninth abdominal segment.

Bionomics. Habitat: mesic and humid meadows, shore vegetation alongside waterpools, brooks and rivers from planar to montane zone. Polyvoltine, flight period from the end of April to the beginning of September. Host plants: Myosotis palustris , M. arvensis ( LORENZ & KRAUS 1957) .

I collected the larvae abundantly on Myosotis palustris in September beside the shore of the pool in Karlštejn NNR and in July in a humid meadow in Částrovické rybníky NR. The larvae rest oustretched on the lower side of the leaf and are detectable by the characteristic sceletonized holes. The larva is inactive, falling down to the herb litter if disturbed and resting here with outstretched body for a long time. The mature larvae burrow into the soil, forming a firm cocoon for hibernation in the prepupal stage.

Discussion. The larva was first described by LORENZ & KRAUS (1957) and supplemented with some other additional characters by VIKBERG & NUORTEVA (1997). However there are some discrepancies in description of the third abdominal segment between these authors, caused by their different conventions for numbering the annulets: annulet 3 in the latter publication is annulet 2 in the former. The redescription provided here is more easily comparable with the description of B. annulitarsis .

Figures

Figs 1–2. 1 – Birka annulitarsis (Thomson, 1870), 2 – Birka cinereipes (Klug, 1816): a, d, e – mounted larva from alcohol; b, c – living larva; a, c – lateral view; b – dorsal view; d – frontal view; e – abdominal segment IX, dorsal view. Scale: a – 5 mm; b, c – 10 mm; d, e – 1 mm.