Sweden, Finland, Germany.

Saprophagous species, obligate breeder on horse dung.

An excellent description of Z. inexpectata was provided by Pont (1987) and further discussed in relation to other sepsid genera in Pont and Meier 2002. The specimens from Finland and Sweden fit the descriptions well, but we are here nevertheless providing a high-resolution image of the male lateral habitus (Fig. 3a) and ventral abdomen (Fig. 3b) based on specimens acquired from Finland in 2014 because such images can serendipitously capture morphological differences that may become important in future research Ang et al. 2013a. This image is also placed on the digital reference collection for the Sepsidae, Sepsidnet Ang et al. 2013b​.

a

b

Figure 3.

Adult male Zuskamira inexpectata. Images are also displayed as a plate in the species entry for Sepsidnet.

a: Lateral habitus  
b: Ventral abdomen (posterior section)  

Zuskamira inexpectata appears to have fairly specific habitat requirements while many other sepsid species are generalists, are found in many habitats, and can be bred on bovine dung (Pont and Meier 2002). Exceptions include Orygma luctuosum Meigen, 1830 which only breeds on beached kelp-wrack and some Themira species that only breed on waterfowl dung (Pont and Meier 2002). Zuskamira inexpectata appears to be an obligate specialist for horse dung. This is shared with Ortalischema albitarse Zetterstedt, 1847 while Susanomira caucasica is now also known from cow dung (pers. comm., A. Pont). Another unusual life history feature of Z. inexpectata is that the puparia require a winter for diapause before the adult stage emerges (Pont and Meier 2002). The narrow choice of substrate and habitat may explain why Z. inexpectata appears overall fairly rare and why only two specimens were caught in Finland in late August 2011. This is also reflected in the low numbers recorded by Stuke (2005) in Germany.

Initially, Z. inexpectata had a very limited known distribution, lying within Sweden in a narrow 59°N - 61°N latitudinal band from Klacka-Lerberg to Sälen (Pont 1987). The findings by Stuke (2005) expanded the species limits ca. 900km south to 51°N (Nieste, Germany). Our findings further expand Z. inexpectata’s distribution latitudinally, across the Baltic Sea into Southern Finland (Fig. 1).

It is possible that Z. inexpectata is actually currently expanding its distribution, given that European Sepsidae has been extensively sampled (Pont and Meier 2002), and no Z. inexpectata have been found outside of Sweden until 2005. Climate has often been an effective barrier for dispersal (e.g., McGlynn 1999, Ang et al. 2008, Kobelt and Nentwig 2008, Smith et al. 2007), but it is not the case here: the Finnish locality is within the latitudinal range of the Swedish distribution and has a similar climate, while the German localities do not have drastically different (and in fact, milder) climates than the localities in Sweden and Finland.

As mentioned earlier, Z. inexpectata is dependent on horse dung for breeding - one may speculate that the species is being spread to new areas as a synanthrophic commensal alongside equestrian activities, given that humans commonly transport arthropods to new areas (McGlynn 1999, Smith et al. 2007, Ang et al. 2008, Kobelt and Nentwig 2008). It is thus conceivable that Z. inexpectata may eventually be found in other countries in Western Europe and Scandinavia.​

Based on his original description, Pont (1987) collected Z. inexpectata from (S1) Klacka-Lerberg (Västmanland, 22.vi.1986), (S2) in Sälen district, “3km west of Horrmund” (Dalarna, 5.vii.1986) and (S3) near Tierp (Uppland, 9.vii.1962). RM collected additional specimens from (S4) Lima (Dalarna, vi.1999). Surprisingly, Stuke (2005) also recorded additional specimens in the German states of Lower Saxony, from (G1) "Endschlagbach 1 km W Nieste", (G2) Holmer Fischteiche and (G3) Leer, Logaerfeld as well as (G4) "E Flensburg Rothenhaus, NF3375" in Schleswig-Holstein. In 2011, a field collection trip by Ang in Southern Finland yielded two specimens of Z. inexpectata from (F1) a horse farm in Lohja (Uusimaa, sub-Helsinki region. A subsequent field collection trip by Ang to the same locality on 28.vii.2014 yielded many additional specimens. The same trip also yielded Z. inexpectata from (S5) Orsa County (Dalarna) in Sweden. These records currently constitute all the known collecting localities for Z. inexpectata (Fig. 1).

Despite exploring numerous (including previously sampled) pastures, only one pasture in Sweden yielded small numbers of Z. inexpectata specimens during our 2014 collecting trip. The collected specimens were almost always seen on the horse dung itself or in the immediate surrounding vegetation. Sweep-netting of vegetation even a meter away from horse dung almost never yielded this species. The microhabitat was also specific: only fairly fresh piles of horse dung (i.e., still moist on the exterior) in moist -but not flooded- pastures with relatively short grassy vegetation or hay, and close-by to wooded or bushy areas (see Fig. 2) yielded specimens. Furthermore, specimens were collected only during sunny, warmer periods of the day. Overall, the species initially appeared fairly rare in Finland when only two specimens were collected while other sepsids, such as Themira annulipes (Meigen 1826), were very common. However, during the trip in July 2014 the reverse was found as Z. inexpectata was fairly common while T. annulipes was rare.​

An updated checklist based on previous records (Pont and Meier 2002, Ozerov 2005, Kahanpää and Winqvist 2014) indicates that Finland is home to 33 species of Sepsidae across 7 genera (see Table 1​ for list of species).