Pseudoheptamelus runari Conde, 1932

Vikberg, Veli & Liston, Andrew D., 2009, Taxonomy and biology of European Heptamelini (Hymenoptera, Tenthredinidae, Selandriinae), Zootaxa 2112, pp. 1-24 : 15-17

Pseudoheptamelus runari Conde, 1932

Pseudoheptamelus runari Conde, 1932: 13 –15. 1 female and one male syntype, type locality: Lettland [ Latvia], “Gemeinde Buschhof (Birzi)” and “Bei Jakobstadt [now Jekabpils]. Warsgaun-See”.

Pseudoheptamelus runari: Verzhutskii, 1981: 76 –78; description of egg, larva and bionomy.

Pseudoheptamelus runari: Togashi, 1997: 831 –833.

Heptamelus (Pseudoheptamelus) runari: Zhelochovtsev, 1988: 176 .

Heptamelus runari: Blank, 1998: 213 .

Notes on original description and type material. Conde (1932) described the species from two syntypes collected in SE Latvia; a female from Birzi and male from near Jekabpils; coordinates of Jekabpils 56°28’N 25°58’E, with Birzi situated some 15 km SW.

We have not examined the syntypes, stated by Conde to be deposited in “collectio auctoris”. Possibly they no longer exist. At least part of Otto Conde’s personal collection was deposited, possibly as early as 1944, in the Zoological Museum, Berlin, but no definite information is available on the fate of the types of P. runari . However, the original description of P. runari is detailed and illustrated with several line drawings, making the identity of the species clear.

Re-description [ Figs 16, 17 ]. (see key above and the following supplementary notes)

Body length: female 5.1–6.1 mm (n = 14 females from Finland and adjacent Russia), male 4.3–5.2 mm (n = 33 males from Finland).

Colour. Female. Black except for yellowish white: mouthparts, labrum, clypeus, pronotum (broadly), tegulae, legs (except for infuscate extreme base of all coxae and more or less tarsus3 and apex of tibia3. Venation including forewing stigma largely dark; stigma narrowly whitish at base. Abdomen with contiguous red-brown medial markings on dorsum of terga3–5. Apex of abdomen around sawsheath brown. Scape, pedicel and antennomere3 basally black, remainder of flagellum brownish.

Male. Very similar to female, but abdomen darker, with pale colour more whitish and on terga3–5 restricted to apices.

Variability. Except in size, both sexes vary only very slightly in colour or surface sculpture in Finland.

Comments. Togashi (1997) described the only other known Pseudoheptamelus species; P. seiyamai from Shikoku and Honshu, Japan. He examined a male and female of P. runari from Finland and found female P. seiyamai to be larger (7 mm), with abdomen much darker and with different penis valve. P. seiyamai therefore appears to be a distinct species.

Sex ratio. Approximately 1: 2 (female n = 20, male n = 38; mostly collected in Finland).

Hostplant. Athyrium (Verzhutskij 1981) ; Athyrium filix-femina ; larva is an external feeder which gnaws holes on petiole and rachis and often feeds on dried pinnae of the leaf (Verzhutskij 1981; VV, pers. obs., below).

Observations on biology. Found in the fern grove of Hangastenmäki since 2000. Most adult specimens swept from lady ferns; only one female seen flying near ground between lady ferns, followed soon by a male on the same route, both of which were netted. Larva not yet found under natural conditions: only known from specimens obtained in two oviposition experiments in 2001.

Oviposition experiment 5/01: 1Ψ 23.5.2001 captured on lady fern. Leaves of potted lady fern were offered; 25–28 long, apical part unopened, curled downwards. Female was placed on the fern and at 18.00 local time began to lay eggs; 3 in upper side of rachis between 4th and 5th uppermost pinnae. Her head was directed downwards during egg laying. The eggs are placed in the concavity of the rachis, completely embedded below the surface; they appear dark below the thin covering of plant tissue, and as they swell a little, the plant tissue covering and immediately around the egg turns blackish; eggs are separated by a space which is longer than length of an egg. Laying of one egg required 2 min. After laying some eggs the female began to work on adjacent pinnae, using her saw to make small cuts in many of the uppermost pinnae near their bases. Cuts were made from upper surface and also from under surface. Female also made cuts on rachis above the eggs. She subsequently laid two eggs in the other side of rachis, with head upwards. After one day the leaf of lady fern assumed a characteristic appearance: the downturned apex of rachis with unopened pinnae was entirely dried out, apical pinnae below it were also more or less moribund or dead, except for one or two basal pinnulae and 1–2 lowermost pinnae which remained green. The female laid eggs in four leaves out of five, with about 9 eggs in the same rachis before it was killed and preserved next morning at 0 9.00.

The first larvae were observed on the morning of 3.6.; they emerged from lateral upper side of rachis, or sometimes from convex lower side. Body grey, with dark head; thorax distinctly swollen. Larvae readily ate dry pinnulae and also began to gnaw holes on convex underside of rachis.

First moult on 3.6.–5.6.; second moult 7.6.–10.6. (20 larvae counted on 10.6.); third moult 12.6.–14.6.; fourth moult 17.6.–19.6. Specimens of shed skins of every moult were preserved dry (glued to apex of triangular piece of paper). Three shed larval skins of 4th instar were dry prepared by blowing air through anterior end above hot toaster.

The larvae are very slow moving; often several are found close to each other on a rachis. The holes which they gnaw on underside of rachis can be quite large (approx. 2–4 mm long, 1–1.4 mm wide and 1 mm deep). The head of the larva is small and can be drawn totally within the prothorax; when gnawing the rachis the head may be completely inside the hole. Some larvae were placed in petri dishes and cut parts of leaf offered as food; they often began to gnaw a hole in the cut end of the rachis. The larvae feed mainly on dried parts of the fern, but to a smaller extent also on green pinnulae.

Oviposition experiment 10/01: 1Ψ 1.6.2001 captured on lady fern. Indoors, it laid eggs in 4–5 fronds between 18.00 on the day of capture and 0 9.00 the following day. The downturned apical part of leaf and uppermost pinnae dry out and die as a result of the incisions made by female following oviposition, only 2–3 lower pinnae remain green.

Only one larva was found, on 14.6. On 9.7. the full grown larva (6th instar) was photographed ( Fig. 22 ). On the evening of the same day it stopped feeding, emptied its gut (with no extra moult) and thereafter walked slowly and incessantly, seeking a place to pupate. It was dry-prepared by blowing air into the empty skin, and although this did not succeed very well, the original colours remained.

Six feeding larval instars were observed, confirmed by measurement of width of frons (mostly in cast larval skins), and in many cases also widths of head and length of body:

1st instar: frons width 0.22–0.24 mm (n = 7),

2nd instar: frons width 0.28–0.30 mm (n = 9), head width 0.5 mm, body 3.6–4.6 mm,

3rd instar: frons width 0.33–0.37 mm (n = 16), head width 0.67–0.70 mm, body 6.3–7.2 mm,

4th instar: frons width 0.40–0.44 mm (n = 8), head width 0.87 mm, body 8.8–9.2 mm,

5th instar: frons width 0.47–0.49 mm (n = 3), head width 0.90–0.95 mm, body 8.6–10.6 mm,

6th instar: frons width 0.55 mm, head width 1.10 mm, body 11–12 mm (n = 1).

The widths and heights of some segments of the living larva of 6th instar were measured: (widths) prothorax 1.4 mm, metathorax 2.3 mm, anterior abdomen 2.2 mm, segment9 1.4 mm, anal segment 0.8 mm; (heights) metathorax 2.4 mm, anterior abdomen 2.0 mm, segment8 1.6 mm, segment9 1.4 mm, anal segment 1.0 mm. Because males are smaller than females, it seems probable that they have 5 larval instars and female has 6 larval instars, but to confirm this, more experiments are needed.

Figures

FIGURES 15 – 19. 15, H. ochroleucus, ♂ (Germany, Bavarian Forest National Park), lateral; 16 – 17, Pseudoheptamelus runari Conde (Finland, South Häme, Janakkala, Hangastenmäki, leg. VV). 16, Ψ, dorsal; 17, sawsheath, lateral. 18 – 19. 18 – 19, Larva of H. dahlbomi (Finland, Hangastenmäki). 18, immature larva, anterior, lateral; 19, last feeding larval instar, lateral. Scale bars = 0.5 mm.

FIGURES 20 – 22. Larva of P. runari (Finland, Hangastenmäki: all images of same individual). 20, lateral; 21, dorsal; 22, live larva on foodplant. Scale bar = 1 mm.