Stauronematus platycerus ( HARTIG , 1840), 2007

Liston, Andrew D., 2007, Revision of Stauronematus B, 1953 and additions to the sawfly fauna of Corsica and Sardinia (Hymenoptera, Tenthredinidae), Beiträge Zur Entomologie = Contributions to Entomology 57 (1), pp. 135-150 : 139-142

Stauronematus platycerus ( HARTIG, 1840) sp. rev., comb. nov.

Nematus platycerus HARTIG, 1840: 27 , , type locality: North Germany [according to introduction]. The name platycerus is to be treated as a noun. Synonymised by CAMERON (1885: 55) with Nematus compressicornissicornis auct.

Nematus vallator VOLLENHOVEN, 1858: 191-194 ,   larva, hostplant Populus nigra var. italica , type locality: Den Haag, Netherlands. Synonymised by CAMERON (1878: 267) with Nematus compressicorniscompressicornis auct. Lectotype designated by THOMAS (1987).

Nematus callicerus THOMSON, 1863: 619-620 , , type locality: Ringsjön, Scania, Sweden. Synonymised by CAMERON (1885: 55) with Nematus compressicornis auct.

? Nematus cebrionicorniscebrionicornis A. COSTA, 1859: 20 , , type locality: Camaldoli Hills, near Naples, Italy. Synonymised by CAMERON (1885: 55) with Nematus compressicornis auct.

Nematus compressicornis : misidentification by CAMERON (1878: 267).

Lygaeonematus compressicornis: KONOW (1890: 247) .

Stauronema compressicornis: BENSON (1948: 22) .

Stauronematus compressicornis: BENSON (1953: 153) .

Pristiphora compressicornis: MUCHE (1974: 62) .

PristiphoraPristiphora ( Stauronematus )) compressicornis: MUCHE (1977: 313) .

NematusNematus ( Stauronematus )) compressicornis: ZHELOCHOVTSEV (1988: 144) .

Lygaeonematus platycerosplatyceros (HARTIG) : KONOW (1890: 247), misspelling.

Type material examined

Nematus platycerus HARTIG. Lectotype (here designated) : [red, printed] "Cotype", " Nematus platycerus HTG, Th. HARTIG det.", " Lygaeonematus compressicorniscompressicornis F. , E. CLÉMONT det.", "platycerus m.", [printed] "Sammlung Th HARTIG", " Lectotype Nematus platycerus HARTIG, 1840 designated LISTON 2006", "GBIF-GISHym 3385", ZSM. Condition: missing are right posterior leg apart from coxa and trochanter, tarsus of left posterior leg.

Nematus vallator VOLLENHOVEN. Lectotype (designated by Thomas 1987) : [red] "Museum Leiden, Syntype, Nematus vallator VOLLENHOVEN 1858 ", [green, round] "v. Voll. Leyd. 6", " Lygaeonematus vallatorvallator v. VOLL. Det.", " Lygaeonematus compressicornis FR.  ", " Stauronematus compressicornissicornis ( FABR..),  det. P. THOMAS XII. 1985 ", " Lectotype P. THOMAS 1986", RMNH. Condition: good, but partly faded body colour (black has become brown).

Nematus callicerus THOMSON. Lectotype (here designated) : small square label with green upperside, " Lectotype Nematus callicerus THOMSON, 1863 designated LISTON 2006", " Stauronematus platycerusplatycerus ( HARTIG, 1840)  det. LISTON 2006", MZLU. Good condition. All specimens under the name Nematus calliceruscallicerus in the THOMSON collection were examined. Only the second specimen in the series can be regarded as a syntype. The small green label indicates that this was collected at the type locality Ringsjön (R. DANIELSSON, pers. comm.). A second male specimen with a similar green label can not be regarded as a syntype, because THOMSON only described the female sex.

Nematus cebrionicornis COSTA was not available for examination. CAMERON’s synonymy of this taxon with Nematus compressicornis seems justified. The description of the thorax as completely black except for the pale tegulae corresponds with S. platycerus , but not with S. saliciphilus sp. n. GHIGI (1905) in a revision of material including COSTA’sCOSTA’ types held by the Naples Museum, did not mention cebrionicorniscebrionicornis by name, but lists a male or males which he identified as Lygaeonematus compressicornis (F.) from Camaldoli (the type locality for N. cebrionicornis as given by COSTA).

Diagnostic combination (see also key, above):

Most valuable single external character for separating S. platycerusplatycerus from S. saliciphilus , in both sexes, is the colour of the pronotum. This is black in platycerus , at most edged with a dull brown tint, and clear white or yellow in saliciphilus . Shape of the head behind the eyes, although slightly variable in both species, is much more sharply contracted in the female of saliciphilus . This difference is not so pronounced in the males. The entirely glabrous patch on the lower part of the mesepisternum typical of saliciphilus is not completely constant: one female from Sardinia has no such patch. Conversely, S. platycerus normally has the mesepisternum entirely pubescent although two female specimens of a total of 47 examined possess a non-pubescent area. The slightly darker wing membrane of saliciphilus appears to be a constant character, but is difficult to appreciate unless specimens can be compared directly.

The gross morphology of the lamnium of the female lancet appears to be constant in both species (3 specimens of saliciphilus and 9 platycerusplatycerus examined). Stauronematus saliciphilus has 16 serrulae, S. platycerus 19. The reduced number in S. saliciphilus is compensated by an increase in their size, so that the length of the spaces between the serrulae relative to the length of a serrula is similar in both species. The penisvalve of S. saliciphilussaliciphilus is very similar to that of S. platycerus . Further males of saliciphilus will have to be obtained in order to reveal whether the apparent difference in the outline of the ventral edge of the paravalva is a useful character for distinction of the species.

Variability:

In all German specimens examined, the pronotum is completely black. BENSON (1958) and ZHELOCHOVTSEV (1988) state that the corners of pronotum are yellow. MUCHE (1974) noted this discrepancy, stating that in the material which he had seen, the pronotum is all black. According to CAMERON (1885: 48, key) the pronotum is entirely black. About half of the specimens examined from Sweden and the Netherlands have brown upper and rear edges of the pronotum, in the others the pronotum is completely black. V. VIKBERG (pers. comm.) noticed a similar testaceous colouration in all of ten specimens reared in Helsinki from Populus tremula and one captured male and female from Slovakia. The mesepisternum is usually slightly pubescent on lower half, rarely with glabrous patch. Rear femur usually entirely pale, occasionally with a dorso-apical black spot. The labrum may be black or brownish.

Distribution: Apparently ppar widespread in the Palaearctic (TAEGERTAEGER et al. 2006; VERZHUTSKII 1981; XIAO et al. 1992). Material from the following countries has been examined: Norway, Sweden, the Netherlands, Germany, France, Turkey and China.

Hostplant: Oligophagous on various species of Populus . Sometimes a severe pest in plantations of poplars, particularly when the trees are young ( GEORGIEV 1990; EWALD 2003). Records from SalixSalix require confirmation.

Larva and biology: Larva is described by LORENZ & KRAUS (1957) and CAVALCASELLE (1968). Its biology has been investigated by numerous entomologists, e.g. VOLLENHOVEN (1858), LOISELLE (1909), CAVALCASALLE (1968), GEORGIEV (1990), BLOEMSMA & HOGENES (1997).

Stauronematus saliciphilus sp. n.

= Stauronematus compressicornis: LISTON & SPÄSPÄ ÄTHTH, 2005 misidentification.

Description

Body length: 5.0- 5.5 mm.

Colour: black. Labrum pale brown. Pronotum almost completely white or bright yellow ( Figs 9 , 10). Tegulae of the same colour as pronotum. Legs yellow; apical third of rear tibia and entire rear tarsus infuscate; all coxae yellow except for extreme base. Female abdomen black with at least the hypopygium and its immediate surroundings brown, or entirely yellow except for the following fuscous markings; parts of terga 1-2 (3rd very slightly) and 7-8, dorsoapical portion of sawsheath ( Figs 11 , 12). Male abdomen with subgenital plate and harpes brown. Stigma and venation fuscous except for paler costa and subcosta. Wing membrane slightly darkened.

Head in dorsal view strongly contracted behind eyes in female ( Fig. 9 ) and male (Fig. 10). Malar space as long as diameter of front ocellus. Interantennal area with lateral carinae, converging below; separated from frontal area by a weak ridge. Clypeus subtruncate. POL: OOL: OOCL as 1.0: 0.64-0.66: 0.36-0.48 (female) 1.0: 0.58-0.62: 0.30-0.35 (male). Punctation on head, pronotum and mesonotum weak; these parts strongly shining. Pubescence pale, shorter than diameter of an ocellus. Mesepisternum densely pubescent on upper half, usually abruptly entirely glabrous below this, with a few hairs on extreme lower edge. Without punctures or sculpture. Front mesonotal lobes with medial furrow shallow, obsolete on extreme posterior. Inner hind tibial spur 0.45-0.50 as long as basitarsus. Outer spur 0.55-0.65 as long as inner. Abdominal terga, except for smooth tergum 1, with weak coriaceous sculpture at 90X magnification. Terga 1-5 with very sparse pubescence, apical tergites progressively more pubescent. Cerci longer than projecting part of sheath. Sawsheath in dorsal view with longer setae arising at an angle of about 80° to one another, curved so strongly that their apices are slightly convergent. Lancet of ovipositor ( Fig. 13 ) with 16 annulets. Penisvalve ( Figs 14 , 15 ), ventral margin of paravalva emarginate.

Etymology: adjective, meaning having a liking for Salix .

Diagnostic combination: see key and under S. platycerus (above).

Variability:

One of the Corsican females has the abdominal terga posterior to tergum 2 dark brown, but the Corsican specimens all have a very much darker abdomen than the two females from Sardinia. All the pale body parts in the Sardinian specimens are a more reddish-yellow (orange) than the pale yellow of those from Corsica. Although the glabrous patch on the lower half of the mesepisternum seems to be a useful character for distinguishing the two species, one of the Sardinian S. saliciphilussaliciphilus lacks this, as in most specimens of S. platycerus . The colouration of the Sardinian specimens of S. saliciphilussaliciphilus is so strikingly different from those from Corsica, that it seems possible that they might represent a distinct geographical race, but they are considered to be conspecific, because their morphology is very similar. More material and biological information for the Sardinian population should be sought.

Holotype (female): Corsica: Tamaricciu-Tal [ Tamaricciu Valley ], SW Porto Vecchio, [reared] ex ova an Salix atrocinerea , coll. 11.04.2005, em. 05.2005, leg. J. SPÄSPÄ ÄTHTH ( DEI).

Paratypes: Corsica: Tamaricciu-Tal, SW Porto Vecchio, [reared] ex ova an Salix atrocinerea , coll. 11.04.2005, 2  1  em. 05.2005, leg. J. SPÄSPÄ ÄTHTH ( DEI, JS) ; River Figurella near Calvi, 1 , 29.04.2004, leg. LISTON ( DEI) . Sardinia, Sta. di Villagrande , 9 km NW Lanussei, swept from Salix purpurea , 2 , 17.04.2006, leg. LISTON ( DEI) .

Hostplant: Salix atrocinerea , possibly also S. purpurea . At the Sardinian locality both these willows occur, but PopulusPopulus is absent.

Larva and biology (based on observations by J. SPÄSPÄ ÄTHTH): Feeding habits very similar to those of S. platycerus . Eggs are laid on the leaf underside, in the side of the midrib, often in pairs ( Fig. 16 ). Apparently the leaf illustrated in Fig. 16 was laid on twice. Young larvae feed on the edges of holes made in the leaf-blade ( Fig. 17 ), later instars feed on leaf edges. The emergence of

imagines (Corsican syntypes) shortly after collection of the larvae, indicates that S. saliciphilus , like S. platycerus , has more than one generation per year.

Distribution: Corsica and Sardinia.

Comments

In addition to literature records of larvae of S. platycerusplatycerus (as Lygaeonematus or Stauronematus compressicornis )) from various species of Populus , of which P. tremula is most frequently mentioned, several previous authors have recorded SalixSalix as a host. The first such mention seems to be by BENSON (1948), repeated in BENSON (1958). He does not state the source of his information. Many of the subsequent indications of SalixSalix as a hostplant in the European literature, few of which seem to be based on original data, probably result from BENSON’s publications. The only published primary data known to the present author which indicate SalixSalix as the natural host of Stauronematus (under S. compressicornis )) are by OKUTANI (1967: Salix alopechroa ), CAVALCASELLE (1968: Salix viminalis )) and XIAO et al. (1992: Salix matsudana ). GEORGIEVGEORGIEV (1990) wrongly lists Salix alba , misquoting CAVALCASELLE (1968) who mentions only Populus alba . PSCHORN-WALCHER & ALTENHOFER (2000) record that larvae of Stauronematus platycerus in Central Europe usually feed on Populus tremula , more rarely P. nigra , but were capable of surviving on Salix purpurea in rearing experiments. In the light of the results presented here, the identity of StauronematusStauronematus specimens associated in nature with Salix should be checked.

SCOBIOLA-PALADE (1981) and LACOURT (1999) state that S. platycerus (as S. compressicornis )) has a Holarctic distribution, probably based on BENSON (1958). GOULET (1992) mentions the occurrence of Stauronematus in Canada, but this is definitely based on BENSON (1958) (H. GOULET, pers. comm.). Neither H. GOULET nor D. R. SMITH (pers. comm.) knows of any definite Nearctic records. BENSON (1962), in a review of Holarctic Symphyta , makes no mention of Stauronematus , so at present it seems best to regard his earlier mention of a Holarctic distribution as mistaken.

Figures

Fig. 9: Stauronematus saliciphilus sp. n. Female Fig. 10: Stauronematus saliciphilus sp. n. Male head head and pronotum. Scale, 0.1 mm. and pronotum. Scale, 0.1 mm.

Fig. 11: Stauronematus saliciphilus sp. n. Female Fig. 12: Stauronematus saliciphilus sp. n. Female (dorsal). Scale, 1.0 mm. (lateral). Scale, 1.0 mm.

Fig. 13: Stauronematus saliciphilus sp. n. Female lancet.

Fig. 14: Stauronematus saliciphilus sp. n. Male penisvalve.

Fig. 15: Stauronematus saliciphilus sp. n. Penisvalve (detail).

Fig. 16: Stauronematus saliciphilus sp. n. Egg pustules in midrib underside, Salix atrocinerea.

Fig. 17: Stauronematus saliciphilus sp. n. Young larvae on Salix atrocinerea.