Heterarthrus leucomela (Klug, 1818)

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 : 99-101

Heterarthrus leucomela (Klug, 1818)

Tenthredo (Emphytus) leucomela Klug, 1818: 274. Holotype ♀, in ZMHUB (examined). Type locality: Silesia (now Poland). Note: the name is a noun and therefore not declinable.

Heterarthrus leucomelus (Klug, 1814), misspelling. Altenhofer & Zombori (1987: 186-188): description of adult, larva and biology.

Phyllotoma aceris Kaltenbach, 1856: 257-258. Syntypes (sex not stated), larva, host Acer pseudoplatanus . Type material apparently lost. Type locality not stated (but presumably Germany, according to title of the work). New synonym.

Type material examined.

Holotype Tenthredo (Emphytus) leucomela : ♀ "Silesia m. Kl.", "Leucomela Kl", “14138”, “GBIF-GISHym2425” (ZMHUB).

Other material examined.

Austria: Upper Austria: 8♀ 3♂, Linz , larva ex Acer pseudoplatanus , 08.1976 (em. 13.5.1977), leg. E. Altenhofer (HNHM) . 4♀ 5♂, Linz , larva ex Acer campestre , 12.09.1976 (em. 7.5.1977), leg. E. Altenhofer (HNHM). Salz burg : 2♀, Straßwalchen, larva ex Acer campestre , 25.08.1977 (em. 3.05.1978), leg. E. Altenhofer (HNHM) . 1♂ (DEI-GISHym31981), Puch bei Hallein , reared Acer pseudoplatanus , 02.08.1975, leg. E. Altenhofer (SDEI) . Lower Austria: 1♀, Riedenberg , reared ex Acer campestre , 08.08.1975 (em. 24.5.1976), leg. E. Altenhofer (private collection M. Viitasaari) . 1♀ (DEI-GISHym31980), Etzen , reared ex Acer pseudoplatanus , 02.09.1988 (em. 25.04.1989), leg. E. Altenhofer (SDEI) .

Germany: Bavaria: 1♀ (DEI-GISHym19032), Dingolfing, Alm, ovipositing in A. pseudoplatanus leaf, 15.05.2004, leg. A. Liston (SDEI) . Thuringia: 1♀ (DEI-GISHym83894), Luisenthal, 24.05.1986, leg. L. Behne (SDEI) .

Remarks.

The fate of the type material of Phyllotoma aceris Kaltenbach, 1856 is not known. According to Horn et al. (1990), the Kaltenbach Collection was auctioned in London in 1880. The description by Kaltenbach (1856) has in the past been misinterpreted, or overlooked, partly because it appeared in a rare journal which is not available in most libraries. By contrast, the book with the same title, by Kaltenbach (1874), was a widely available and popular work of reference. In Kaltenbach (1874), P. aceris is still referred to as a new species. As a result of this, subsequent taxonomists who were unaware of Kaltenbach’s 1856 description regarded Phyllotoma aceris Kaltenbach, 1874 as a junior homonym (and usually also a synonym) of Phyllotoma aceris McLachlan, 1867. All authors of this period assumed that only a single species of Heterarthrus occurred on maples. It is important to note that whilst the description of the adult is exactly the same in both Kaltenbach publications, the description of the early stages is more extensive and the biology is described significantly differently in the work of 1874. Either Kaltenbach (1874) had found more material during the intervening years, but failed to recognize that this new material belonged to a species of Acer -feeding Heterarthrus different to the one which he originally described, or perhaps he revised his text in the light of the observations published by Healy (1867) on the biology of P. aceris McLachlan. Altenhofer and Zombori (1987) were sure that the latter explanation is correct. Whatever the reason for the differences between the two Kaltenbach descriptions, only the first description published in 1856 is relevant when considering the identity of P. aceris Kaltenbach. The text in Kaltenbach (1856) reads (translated from German):

" Phyllotoma ( Emphytus not Ericampa as on p. 176) Aceris m. The yellowish larva lives in July and August as a mini-caterpillar in the leaves of sycamore ( Acer pseudo-plantanus [sic!]). It eats out large areas between the two skins of the leaf, which become noticeable as wan [falbe (sic!), probably typographical error for “fahle”], sickly patches on the leaf upperside. To metamorphose, it spins within the mine a circular, flattened cocoon (similar to that of Tischeria complanella in oak leaves, and exactly as in Phyllotoma melanopygus Klg. and Phyl. salicis m. living respectively in the leaves of alder and willow), overwinters as a larva therein and first pupates in the following spring. I obtained the wasp as early as the beginning of May by rearing indoors.

Wasp: black, smooth; antennae 12-membered, towards the apex ringed with brownish; palps whitish, apical member of labial palps black, the thicker basal mem bers of the maxillary palps ringed with black; area of mouth, the inner edge of the green-violet eyes and the tegulae bone-white. Legs black; all knees and the inner sides of the four front legs dirty yellow-white; tarsi brownish to brown. Wings uniformly dark smoky. Length 1.5-2 ’’’ [approx. 3.4-4.5 mm. 1 line = approx. 2.25 mm] ’’.

Most significantly, the cocoon of P. aceris is stated by Kaltenbach (1856) to remain within the leaf, as is indeed the case with H. vagans ( Fallén) (= P. melanopygus (Klug, 1818)) and H. microcephalus (Klug) (= P. salicis Kaltenbach, 1856). In the European Acer -feeding Heterarthrus , cocoons of all species except H. leucomela separate from the leaf and fall to the ground soon after they are formed ( Altenhofer and Zombori 1987). Healy (1867) describes the latter behaviour for P. aceris McLachlan. The relatively late date of collection of Kaltenbach’s larvae only fits the slow larval development recorded for H. leucomela by Altenhofer and Zombori (1987) and Späth and Liston (2003). All other maple-feeding Heterarthrus species finish feeding earlier in the year. Furthermore, only the male of H. leucomela has the pattern of black and white colour on the palps (see Altenhofer and Zombori 1987) which Kaltenbach describes for P. aceris . The relatively small body size given by Kaltenbach (females of H. leucomela are conspicuously larger than other species of aceris group) also indicates that the syntypes of P. aceris were males: Altenhofer and Zombori (1987: 187) give a body length of 3.5-5.5 mm for male H. leucomela and 5.5-7.0 mm for females.

Host plants and biology.

Acer campestre L. and A. pseudoplatanus L. ( Altenhofer and Zombori 1987). Oviposition in the leaf edge. The cocoon remains within the leaf. Univoltine.

Distribution.

Central and south-east Europe ( Taeger et al. 2006).