Heterarthrus fiora Liston, 2019

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 : 93-96

Heterarthrus fiora Liston sp. nov.

Heterarthrus aceris : misidentification. Altenhofer and Zombori 1987: 188-189, figs 2, 5, 6, 14, 15.

Description.

Female ( Figs 15 , 17 , 21 , 24 , 39 - 46 ).

Body length. 3.5-4.5 mm.

Colour. Shiny black and dirty white ( Figs 39 , 43 ). Head: black with the following parts pale: labrum, anterior and lateral parts of clypeus, malar space partly, a band along inner orbit about half way up the eye, a U-shaped fleck on supraclypeal area, labial palpomeres 2 and 3, maxillary palpomeres 3 and 4, base of mandible ( Fig. 40 ). Antenna black with 2-3 apical flagellomeres more or less red-brown ( Fig. 46 ). Thorax: black with the following parts white: very narrow lateral and hind margin of prono tum, margins of tegula ( Fig. 17 ). Legs black; pale are apices of coxae, femora, more or less anterior surfaces of all tibiae. Wings light brownish infuscate, veins and pterostigma dark brown. Abdomen: black. Very narrow posterior edges of terga more or less white. Sterna entirely dark.

Structure. Head: with sparse, silvery pubescence. Frons divided in the middle by a longitudinal depression that is rather broad just below the median ocellus, becoming very narrow ventrally, and ending well before an imaginary line connecting the upper margins of the toruli ( Fig. 40 ). Postocellar area short, medially 1.5 times as long as diameter of an ocellus ( Figs 41 , 42 ). Malar space 0.29-0.33 × as long as height of eye. Head in dorsal view strongly contracted behind eyes. Usually 12 antennomeres, rarely 11 ( Fig. 46 ). Ratio of lengths of flagellomeres 1-8 approximately as: 100, 75, 71, 62, 51, 46, 42, 40. Thorax: Median mesoscutal lobes with straight transverse grooves at about 0.25 from anterior; coriaceous sculpture on anterior two-thirds ( Fig. 17 ). Lateral lobes with lateral longitudinal coriaceous band. Mesoscutellum shiny with sparse, weak punctures, mesoscutellar appendage highly polished. Metascutellum transversally wrinkled. Mesopleuron covered with short pubescence and finely punctate, but pectus bare and shiny. Abdomen: Tergum 1 less densely sculptured than 2, and more distinctly shiny. Terga 2-7 with dense sculpture, but slightly shiny ( Fig. 15 ). Apical terga with very weak sculpture basally, otherwise unsculptured. Hypopygium deeply emarginate medially ( Fig. 24 ). Sawsheath in dorsal view subparallel-sided, with apex blunt ( Fig. 44 ). Setae curved and directed backwards. Lancet with 13 teeth. 8-11 denticles per tooth ( Fig. 21 ). Apical teeth, apart from last two, clearly separated from each other.

Male. Unknown: the species is exclusively parthenogenetic ( Altenhofer and Zombori 1987). Mentions of males under the name H. aceris by, for example, Benson (1952) are based on misidentifications of other Acer -feeding Heterarthrus species (particularly H. wuestneii and H. cuneifrons ) which resemble H. fiora .

Variability.

Examined specimens are all highly similar, with only very slight differences in the extent of the pale pattern on the head.

Holotype: Female. [Four printed labels:] Austria, Kammern, 12.v.1977, leg. Altenhofer. Larva ex Acer pseudoplatanus 8.vii.1976. Heterarthrus aceris Kalt. det. Zombori 1977. DEI-GISHym31975. Deposited in HNHM.

Paratypes: Austria: 7♀ (including DEI-GISHym31976, 31977, 83900) same collection data as holotype, but only one specimen with label indicating that it was determined as H. aceris by L. Zombori. Deposited in HNHM, except for one specimen, without head, in SDEI. Ireland: 1♀, Tyrone, Pomeroy, 27.5.1987, leg. A. Liston (NMS). Scotland: 1♀, Edinburgh, Corstorphine Hill, ovipositing in leaf edge of Acer pseudoplatanus , 1.6.1979, leg. A. Liston (NMS).

Diagnosis.

Very similar to Heterarthrus wuestneii and Heterarthrus cuneifrons in size, colour, and external morphology. The lancet teeth of H. fiora are somewhat angular, each with 8-11 denticles, and the apical teeth, apart from last two, are clearly separated from each other ( Fig. 21 ). The teeth of H. wuestneii and H. cuneifrons are more rounded, lower, with 12-15 smaller denticles, and the apical teeth are not clearly separated from each other ( Figs 19 , 20 ).

Note.

the key by Altenhofer and Zombori (1987) states that H. aceris (= Heterarthrus fiora ) has malar space and entire tegula dirty white, whereas in H. cuneifrons the malar space and basal half of tegula black. These characters are in our opinion not reliable: the tegula of H. fiora is normally dark on the interior and margined with white (as is in fact written in the description of H. aceris by Altenhofer and Zombori, 1987), and H. cuneifrons may also have a nearly completely pale malar space. According to Altenhofer and Zombori (1987) the head of H. aceris auct. is relatively narrowed behind the eyes, like H. cuneifrons , but we are not convinced that any interspecific differences in head shape exist.

Etymology.

The name, to be treated as a noun, is derived from the Scottish Gaelic fìor-chrainn (sycamore tree, Acer pseudoplatanus L.).

Host plants and biology.

Acer pseudoplatanus L.: as recorded by Altenhofer and Zombori (1987), and Späth and Liston (2003). The leaf-mine develops from the edge of the leaf. The circular cocoon, constructed in part from the upper leaf epidermis, separates from the leaf and falls to the ground before the leaf falls from the tree. Univoltine.

Distribution.

Probably widespread in Europe, but many records under the name aceris are unreliable because of nomenclatural and taxonomic confusion.

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 22 - 32. Heterarthrus 22 - 24 hypopygia: 22 H. wuestneii DEI-GISHym 20656 23 H. cuneifrons DEI-GISHym 31984 24 H. fiora sp. nov. DEI-GISHym 31976 25 - 28 valvulae 3 dorsal: 25 H. microcephalus DEI-GISHym 11397 26 H. leucomela DEI-GISHym 83894 27 H. ochropoda DEI-GISHym 83895 28 H. vagans DEI-GISHym 83896 29 H. leucomela ♀ DEI-GISHym 83894 lateral 30, 31 H. ochropoda ♀ DEI-GISHym 83895 lateral, dorsal 32 H. vagans ♀ DEI-GISHym 83897 dorsal. Scale bar: 1 mm.

Figures 33 - 40. Heterarthrus 33, 34 median mesoscutal lobes ♀: 33 H. ochropoda DEI-GISHym 83895 34 H. leucomela DEI-GISHym 31980 35, 36 head frontal ♂: 35 H. vagans DEI-GISHym 11095 36 H. leucomela DEI-GISHym 31981 37, 38 fore wing ♂: 37 H. ochropoda DEI-GISHym 83898 38 H. microcephalus DEI-GISHym 83899 39, 40 H. fiora sp. nov. ♀ holotype: 39 dorsal 40 head frontal. Scale bar: 1 mm.

Figures 41 - 48. Heterarthrus 41 - 46 H. fiora ♀: 41, 42 head dorsal at different viewing angles, holotype 43 DEI-GISHym 83900 lateral 44, 45 DEI-GISHym 83900 sawsheath dorsal, lateral 46 DEI-GISHym 31977 antenna 47, 48 head frontal ♀: 47 H. vagans DEI-GISHym 11091 48 H. kamtchaticus (H. aihinoensis holotype). Scale bar: 1 mm.