O VORST1 & M SÖRENSSON2 1National Museum of Natural History, Naturalis, Leiden, The Netherlands 2Lund University, Lund, Sweden ON THE IDENTITY OF ACROTRICHIS NANA STRAND, A SPECIES DISTINCT FROM A. DISPAR (MATTHEWS) (COLEOPTERA: PTILIIDAE) Vorst, O. & M. Sörensson, 2005. On the identity of Acrotrichis nana Strand, a species distinct from A. dispar (Matthews) (Coleoptera: Ptiliidae). – Tijdschrift voor Entomologie 148: 329- 333, figs. 1-8. [ 0040-7496]. Published 1 December 2005. Acrotrichis nana Strand, 1946 is reinstated as a proper species distinct from A. dispar (Matthews, 1865) with which it had been previously synonymized. Both species can be reliably separated by primary and secondary sexual characters of the males only. Apart from the single type specimen from southern Norway, A. nana has recently been discovered at two localities in the south of Sweden and in the Netherlands. The availability of extensive material from the latter country, all collected at National Park ‘Veluwezoom’, made the recognition of its true status possible. A large proportion of the specimens were found in association with carcasses of large animals (Highland cattle and wild boar). Oscar Vorst, National Museum of Natural History, Naturalis, PO Box 9517, 2300 RA Leiden, The Netherlands. E-mail: [email protected] Mikael Sörensson, Lund University, Zoology bldg, Helgonav. 3, SE-223 62 Lund, Sweden. E-mail: [email protected] Key words. – Acrotrichis; Ptiliidae; West-Palearctis; carrion; synonymy; featherwing beetles. Although ptiliid beetles are mostly very small females) of the new species, its true status became in size (0.5 to 1.2 mm), the North and Central evident. Males can easily be separated by primary and European fauna has been extensively studied. Es- secondary sexual characters. No reliable characters pecially the largest and most difficult genus separating the females of both species could be Acrotrichis Motschulsky, 1848 attracted the attention detected. of some skilled coleopterists. As a result several revi- Most material was collected in the course of an ex- sionary studies treating this genus were published tensive study on the entomofauna of large carcasses during the last century (Roßkothen 1934, 1935, carried out at National Park ‘Veluwezoom’ in the Renkonen 1939, Strand 1941, Sundt 1958, 1971, Netherlands. The focus in this study was on Diptera M´lynarski 1984, Sörensson 1988). Many of these and Coleoptera. The latter were collected from sam- publications present accurate figures of male and es- ples taken by sieving the soil impregnated by body pecially female genitalia that are being used as essen- fluids from the carcasses. This habitat proved to be tial characters for the separation of the often similar particularly rich in ptiliid beetles. Twenty-eight sam- species. In addition, the Acrotrichis-fauna of several ples yielded more than 1800 specimens belonging to other geographic regions has been treated in the past 24 different species. These represent almost half of decades (Sundt 1969, Johnson 1969, 1984, 1985, the Dutch ptiliid fauna, which until now comprised 1988, Sawada & Hirowatari 2002). 48 species (Brakman 1966, Huijbregts & Krikken Thus, we were surprised to discover an unknown 1988, Vorst & Huijbregts 2001a, 2001b). A single species of Acrotrichis in Northwest Europe. A single specimen was caught by ‘Autokätscher’ (car net) on male collected in 1988 and another collected in 1997 the Baltic island of Öland while the second Swedish aroused our suspicion, although they first were taken specimen was found in mouldy grass compost. for aberrant specimens of A. dispar (Matthews, 1865). As the newly discovered species is very similar to Only after the recent collection of additional materi- A. dispar, current synonyms of the latter potentially al, including a large unmixed series (10 males and 12 refer to this species. The last world catalogue of 329 Downloaded from Brill.com10/01/2021 10:03:56AM via free access T E, 148, 2005 12 3 45 67 Figs. 1-7. Acrotrichis nana (1-3, 6) and A. dispar (4-5, 7). Aedeagus (1, 4), male visible sternite 6 (= sternite 8) (2, 5), spermatheca (3) and (male) pronotal side-edge (6-7) at an angle of approximately 45°. Scale = 75 µm (figs 1-2, 4-5) or 100 µm (3, 6-7). Ptiliidae (Csiki 1911) only gives Acrotrichis pumila Collections Thomson, 1862 as a synonym to A. dispar; erro- Natural History Museum, London neously, as Thomson (1862) did not describe this Museum d’Histoire Naturelle, Genève species as new, but just cited the species of that name Nationaal Natuurhistorisch Museum published by Erichson (1845-48) in 1845. Now- Naturalis, Leiden adays, the name pumila Erichson, 1845 is in use as Zoologisk Museum, Oslo the valid name for another Acrotrichis-species. c Collection O. Vorst, Utrecht Two further names have been listed as junior c Collection M. Sörensson, Lund synonyms to A. dispar, viz. Trichopteryx castanea Rey (Rey 1889), recently placed in synonymy with Acrotrichis nana Strand A. dispar by Johnson (2001), and Acrotrichis nana (figs. 1-3, 6) Strand (Strand 1946), previously placed in synonymy by Sundt (1958). Being a junior primary homonym Acrotrichis nana Strand, 1946: 170. Holotype &: : ‘Brönnöy Asker / Andr. Strand’, ‘Acrotrichis / nana n.sp. of the Nearctic Trichopteryx castanea Matthews, 1877 the name castanea Rey can not be used as a substitute. / A. Strand / ’ [red] ( ). [examined] According to Strand (1946) the type material of A. nana consists of a single female specimen (holoty- Material examined. – The Netherlands: Terlet, ( pus). Its spermatheca was illustrated in Strand (1946) Galgenberg, 5.vi.1997, 1 , O. Vorst (c ); Loenen, Loen- ermark, 6.vii.2002, 1(, O. Vorst (c); De Imbosch, Veer- and conforms with the dispar-type. Our study of the tien Bunder, 26.viii.2002, 1(, 29.viii.2002, 1(, type specimen kept at the Zoologisk Museum, Oslo, 30.viii.2002, 1(, 3.ix.2002, 3(, 27.ix.2002, 1(, revealed it as being almost certainly conspecific to the 19.xi.2002, 9(, 4&, J. Newton & L. Joosten (, c); newly discovered species, which should hence be De Imbosch, Veertien Bunder, 14.iii.2003, 4(, O. Vorst named A. nana Strand. In view of the available ma- (c); De Imbosch, Lamsgroen, 9.v.2003, 1(, O. Vorst ( ( terial the type specimen is a slightly aberrant and (c ); Groenendaal, 18.iv.2003, 1 , 8.vi.2003, 1 , 11.vii.2003, 1(, 1&, O. Vorst (c); De Imbosch, remarkably small specimen. However, the surface Imboschberg, 11.vii.2003, 2(, 2&, 8.vi.2003, 9(, 7&, O. structure of its thorax makes it distinct from typical Vorst (c, c); Sweden: Skåne (Scania), Ängelholm, A. dispar and underlines its conspecificity with our 6.vi.1978, 1(, M. Sörensson (c); Öland, Böda, recently collected material. 9.vii.1988, 1(, P. Cederström (c). 330 Downloaded from Brill.com10/01/2021 10:03:56AM via free access V & S: Identity Acrotrichis nana glistening head and a mediofrontal pronotum of much reduced puncturation, in such cases making fe- male identifications almost impossible. However, as a rule the remaining pronotal puncturation of A. dispar is more pronounced than in A. nana. Bionomics All Dutch specimens studied were found in as- sociation with large carcasses of Highland cattle (Bos taurus L.) or wild boar (Sus scrofa L.) in forests on dry sandy soils. A description and photograph of the Highland cattle carcass from which the species was first collected can be found in Vorst & Huijbregts (2001b). During a study of arthropod succession on wild boar carcasses four specimens were captured in a flight interception trap. The first specimen arrived within three days after the time of death (23.viii.2002). Fig. 8. Distribution of Acrotrichis nana Strand. One Swedish specimen was sieved from a mouldy, somewhat warm compost of cut grass situated in a mature plantation of coniferous trees on sandy soil Description close to the North Sea shores of the west coast of the Length 0.66-0.76 mm (from anterior margin of southernmost province of Skåne (Scania). Another labrum to apex of elytra). Very close to Acrotrichis Swedish specimen was caught by ‘Autokätscher’ (car dispar in body shape, size and surface structure. net) driven along a dry pine forest margin in the Aedeagus characteristically shaped with triangular northern part of the Baltic island of Öland, Southeast apex (fig. 1). Visible male sternite 6 (= sternite 8) with Sweden. This lowland forest close to the Baltic sea is a single group of about 25 setae (fig. 2). Spermatheca situated in one of the driest and warmest areas of as in figure 3. Sweden. Differential diagnosis Distribution Externally very similar to Acrotrichis dispar. Males See fig. 8. So far only known from the Norwegian can easily be separated by the shape of the aedeagus, type locality (near Oslo), two distant sites in which has a simple triangular apex opposed to a tri- South and Southeast Sweden and the National partite apex in A. dispar (figs. 1, 4), and the character- Park ‘Veluwezoom’, province of Gelderland, The istic group of setae on visible sternite 6 (= sternite 8) Netherlands, but doubtless overlooked and much which differs both in extent and configuration wider distributed. However, checking of more than (figs. 2, 5). The female spermathecae are seemingly one hundred specimens of A. dispar from various lo- identical. calities in Switzerland preserved in did not External differences are only slight and subject to yield any more A. nana (Sörensson pers. obs.). variation. Generally speaking, the upper surface of A. nana is more shiny, due to less strong puncturation Discussion and microreticulation. This difference is most promi- In view of the current knowledge of the genus nent on the head and the front of the pronotum, Acrotrichis in Northwest Europe it seems rather sur- where the stippled puncturation and microreticula- prising that the specific status of A.