Acrotrichis Motschulsky, 1848

komosiński, Karol & Marczak, Dawid, 1872, Ptiliolum caledonicum (Sharp, 1872) andBaeocrara japonica (Matthews, 1885) (Coleoptera: Staphylinoidea: Ptiliidae) New to Poland, with Additional Polish Records ofAcrotrichis nanaStrand, 1946, The Coleopterists Bulletin 70 (1), pp. 87-90 : 87-90

Acrotrichis Motschulsky, 1848

The genus Acrotrichis is the most species-rich of the Polish ptiliid fauna. So far, 22 species have been noted for Poland ( Burakowski et al. 1978, 2000; Löbl and Smetana 2004; Sörensson 2007). Acrotrichis nana Strand, 1946 was recently recorded from Poland by a single specimen ( Sörensson 2007). It is a smaller species (approximate length 0.7 mm) belonging to the informal dispar species – group (Vorst and Sörensson 2005). This group consists of Acrotrichis dispar (Matthews, 1865) and A. nana , and most likely also A. pumila (Erichson, 1845) and A. brevipennis (Erichson, 1845) (Vorst and Sörensson 2005) . Acrotrichis nana is very close to A. dispar , a species which formerly was considered very rare in Poland ( Burakowski et al. 1978) while lately proven to be the most common representative of the genus in Poland ( Młynarski 1984; Burakowski et al. 2000).

The best distinguishing character for A. nana and A. dispar is the structure of the male aedeagus (illustrations are presented in Vorst and Sörensson 2005). The female spermathecae are very similar, the main difference being a small tubercle on the base of the spermatheca of A. nana ( Sörensson 2007) . Other subtle differences occur in the external microreticulation and punctation of the upper body surface, especially of the head and prothorax. In typical specimens of A. nana , the external upper surface structure is fainter and less pronounced, making the surface appear shinier. Additionally, the prothorax is slightly more convex with curved sides. However, due to high individual variation within A. dispar , including individuals with strongly reduced external punctation and surface microstructure, definite identity assessment of females based on these features may be very difficult or even impossible (Vorst and Sörensson 2005).

Acrotrichis nana was for a long time known only from Norway (type species from the area of Oslo, described by A. Strand). Later, it was recorded in two southern provinces in Sweden (Scania and Öland) and in the Netherlands (Veluwezoon National Park) (Vorst and Sörensson 2005). Recently, it was discovered in Denmark ( Jørum et al. 2006), Finland ( Martikainen 2006), Germany, and Poland ( Sörensson 2007). The Polish record is a male from Małdyty in the Mazurian Lake Dictrict ( Sörensson 2007) ( Fig. 1 ).

Acrotrichis nana seems to be strongly dependent on dry pine forests growing on sandy soils. In these habitats, it occurs in strongly odorous decaying organic matter, such as carrion and compost (Vorst and Sörensson 2005). These observations were confirmed by us since the species was collected only in dry pine forests ( Fig. 2 ).

Material Examined. Mazurian Lake District (northeastern Poland): ad Pawłowo ( Fig. 1 ) (DE53), 8 VIII – 10 IX 1997 – 2 males, leg et coll. K. Komosiński, earth trap with bait (fish), dry pine forest with juniper; Mazovian Lowland (central Poland): Kampinos National Park , Strict Protection Area Sieraków ( Fig. 1 ), forest spatial unit 77 (DC89), 1-31 V 2014 – 1 male, leg K. Komosiński, coll. D. Marczak, collected by window trap, dry pine forest with pine trees over 180 years old, forest spatial unit 100 (DC89), 1-30 IV 2014 – 1 specimen, 1-31 V 2014 – 1 specimen, 1-31 VII 2014 – 2 specimens, leg K. Komosiński, coll. D. Marczak, collected by window traps, 1-31 VII 2014 – 1 male, collected by barrier trap hanging on a pine, dry pine forest with pine trees over 200 years old; Kampinos National Park, Strict Protection Area Kaliszki ( Fig. 1 ), forest spatial unit 25 (DD80), 1-31 VII 2014 – 1 specimen, leg K. Komosiński, coll. D. Marczak, collected by barrier trap hanging on a pine, fresh pine forest with pine trees over 165 years old .

Discovering new species of Ptiliidae in Poland seems likely. Since the year 1925, several immigrant species of Ptiliidae have been found in western and northern Europe, e.g., Bambara contorta (Dybas, 1966) , Bambara fusca (Dybas, 1966) , Ptinella cavelli (Broun, 1893) , Ptinella errabunda (Johnson, 1975) , Ptinella johnsoni (Rutanen, 1985) , Ptinella simsoni (Matthews, 1878) , Ptinella taylorae (Johnson, 1977) , Acrotrichis cognata (Matthews, 1877) , Acrotrichis josephi (Matthews, 1872) , Acrotrichis insularis (Mäklin, 1852) , Acrotrichis sanctaehelenae Johnson, 1972 (Sörensson and Johnson 2004), and Ptinella populicola Vorst, 2012 ( Vorst 2012) . However, before these discoveries, only one immigrant species, Acrotrichis henrici (Matthews, 1872) ( Burakowski et al. 1978) , was found in Poland.

Figures

Fig. 1. Distribution of Ptiliolum caledonicum, Baeocrara japonica, and Acrotrichis nana in Poland.

Fig. 2. Habitat of Acrotrichis nana in Kampinos National Park, Poland.