Heterarthrus cuneifrons Altenhofer & Zombori, 1987

Liston, Andrew, Mutanen, Marko & Viitasaari, Matti, 2019, On the taxonomy of Heterarthrus (Hymenoptera, Tenthredinidae), with a review of the West Palaearctic species, Journal of Hymenoptera Research 72, pp. 83-126 : 91-92

Heterarthrus cuneifrons Altenhofer & Zombori, 1987

Heterarthrus cuneifrons Altenhofer & Zombori, 1987: 193-195. Holotype ♀, in HNHM (examined). Type locality: Austria, Lower Austria, Neulengbach.

Material examined.

Austria: Lower Austria: 3♀, 2♂ (holotype ♀ and paratypes of Heterarthrus cuneifrons ), Neulengbach, ex larvae Acer pseudoplatanus , 05.06.1985 (em. 1986), leg. E. Altenhofer (HNHM) .

Italy: South Tyrol : 2♀ (DEI-GISHym31979, 31984) 3♂ (DEI-GISHym31988), Salurn, reared Acer pseudoplatanus , 07.2000 (em. 04.2001), leg. K. Hellrigl (SDEI) .

Remarks.

Biologically, H. cuneifrons differs from the closely similar H. wuestneii and Heterarthrus fiora , in that it oviposits into the interior of the leaf-blade, whereas the latter oviposit into the margin of the leaf. Furthermore, males of H. cuneifrons and wuestneii are frequent, but not known in H. fiora . Heterarthrus cuneifrons and Heterarthrus fiora have the same host plant species, Acer pseudoplatanus , whereas H. wuestneii uses different species of Acer .

Altenhofer and Zombori (1987) described several morphological characters which they considered to be useful for separating these three species:

- Shape of the sawteeth of the lancet (♀)

- Shape of the hypopygium (♀)

- Shape of the head behind the eyes, in dorsal view (♀)

- Colour of the malar space and tegula (♀)

- Penis valve morphology (♂)

We have already commented (under Character states) on the difficulty of comparing the shape of the head behind the eyes, and on not being able to find the differences in the hypopygium described by Altenhofer and Zombori (1987). In comparing characters between these three nominal species, we relied on reared material from named hosts. Although the sawteeth of H. fiora are clearly more prominent than the flatter teeth of H. cuneifrons and wuestneii ( Figs 19-21 ), we did not find any way of distinguishing the lancets of the latter two from each other. Nor is the colour of the malar space and tegula useful for separating H. cuneifrons and wuestneii, because of wide variability in H. wuestneii . The structure of the lower frons and interantennal area of H. cuneifrons , which according to Altenhofer and Zombori (1987) differs greatly from the other two species, appeared to us to be indistinguishable. Perhaps even more so than with head shape, slight changes in viewing angle and illumination have a major effect on the perception of the shape of the raised and depressed parts of the face. Initially, we thought that some correlation might exist between the proportions of the penis valve parts, and the segregates which Altenhofer and Zombori (1987) called H. cuneifrons and Heterarthrus healyi (= H. wuestneii ). An attempt to quantify this was made by measuring the distance (1) from the tip of the valvura to the highest point on the pseudoceps, and the distance (2) from the highest point on the pseudoceps to the tip of the pseudoceps (see Fig. 69 ). The ratios of (1) divided by (2) were 1.32-1.87 in H. cuneifrons and 1.37-2.42 in H. wuestneii (Table 1 ).

For the moment, we conclude that H. cuneifrons is not distinguishable from H. wuestneii using morphological characters or COI barcodes. Nevertheless, the apparent biological differences make us reluctant to synonymise them. Further examination of their status should be made, including analyses of nuclear DNA.

Host plants and biology.

Acer pseudoplatanus L. is the only recorded host. Oviposition in the middle of the leaf blade, not in the edge. Cocoon falls from leaf before the leaf falls. Univoltine.

Distribution.

Central Europe, south to northern Italy, and in southern England ( Taeger et al. 2006).

Figures

Figures 15 - 21. Heterarthrus ♀ 15, 16 basal abdominal terga: 15 H. fiora sp. nov. holotype 16 H. leucomela DEI-GISHym 31980 17, 18 median mesoscutal lobes: 17 H. fiora sp. nov. DEI-GISHym 31976 18 H. vagans DEI-GISHym 83893 19 - 21 lancets: 19 H. wuestneii DEI-GISHym 31983 20 H. cuneifrons DEI-GISHym 31979 21 H. fiora sp. nov. DEI-GISHym 31976.

Figures 69 - 73. Heterarthrus penis valves 69, 70 H. cuneifrons DEI-GISHym 31988, see H. cuneifrons taxon account and Table 1 for details of measurements 71 H. wuestneii lectotype 72 H. wuestneii DEI-GISHym 31987 73 H. wuestneii DEI-GISHym 31993.