7.b. Tergite 4, and often 2 and 3, entirely 8.a. Genitalia: epandrium arms clearly pale-haired, rarely some black pile near present, about 1/4 of epandrium height, its front margin; genital capsule small surstylus about 1/2 the length of the and flat; genitalia: surstyli as long as epandrium, without dorsal keel (figure epandrium, in side view flattened and 595). Male and female: hind tibia: hair linear (figure 594); hypopygium pale- fringe not so long and normally all haired. 6-7 mm. Central Europe › white (figure 597); habitus figure 599. 6- Pipizella zeneggenensis Goeldlin 7 mm. Europe, Western Siberia › Pipizella viduata Linnaeus (= Pipizella varipes Meigen) Jizz: smaller species. 599. 8.b. Genitalia: epandrium arms very small or absent, epandrium approximately square, surstyli about 3/4 of the epan- drium length, with a dorsal keel (figure 596). Male and female: hind tibia: with a longer hair fringe, many hairs twice as long as the maximum diameter of the tibia, often many of these hairs black and strong (figure 598); habitus figure 600. 7-8 mm. Central Europe, in Asia to Pacific coast › Pipizella virens Fabricius Jizz: larger, stouter species, reminiscent of an Eumerus in flight.

PLATYCHEIRUS

Introduction 600. Platycheirus are small to moderately large hoverflies that live in grasses and herba- ceous vegetation. The abdomen is black, marked with yellow or grey spots, making the abdomen anything from black to almost yellow. Many species feed on the pollen of wind-pollinated plants, such as Salix, Plantago, Poaceae, Cyperaceae. They also visit flowers, for example, Ranunculus and Umbelliferidae. Many stay active dur- ing cold and rainy weather and observa- tions suggest that lower temperatures (16 to 18 oC) are optimal for this genus. The genus contains many species with a bore- omontane distribution. Some have a cir- cumboreal distribution. Platycheirus are rather inconspicuous in figure 599. Pipizella viduata, habitus of male. the field, both because of their small, slen- figure 600. Pipizella virens, habitus of male der and often blackish appearance and (Verlinden). because they tend to remain hidden in

171 the vegetation. They share these features Fagnes. The other species in the group are with Melanostoma, a closely allied genus. (boreo) montane species. A number of Catching the flies often requires sweeping species in this group have a circumboreal a net through the vegetation. A field of distribution and are found in North Plantago may reveal many Platycheirus of America as well. Care should be taken several species! not to overlook North American species, The larvae are aphid predators, mostly e.g. P. nearcticus, P. inversus, P. octavus, P. found in the ground layer (Rotheray, peltatoides (see Vockeroth, 1992). P. peltatus 1993). Some species, such as P. manicatus, does not appear in North America, P. peltatus and P. scutatus are polyphagous, although it is common in Europe. accepting many different species of • Platycheirus clypeatus and lookalikes. aphids. Others are specialists, such as P. ful- Goeldlin de Tiefenau, Maibach and viventris and P. perpallidus. P. fulviventris Speight (1990) described three further feeds on Hyalopterus pruni on mono- species similar to P. clypeatus and P. angus- cotyledonous plants in wetlands. P. perpal- tatus: P. ramsarensis, P. occultus and P. lidus (and P. immarginatus) feed on europaeus. The latter two species appear all Trichocallis cyperi associated with Carex. over Europe (Van der Linden, 1991), and care is required to recognise them in the field. In addition, P. hyperboreus and P. Recognition angustipes belong to this group, but their distribution is more boreal than clypeatus Platycheirus species all need careful identi- and angustatus. Speight and Goeldlin de fication, because there are many looka- Tiefenau remark that P. angustipes replaces likes and many show variation in the P. occultus and P. europeus in wetlands above colour markings. A reference collection 1000 metres in Central Europe. for both males and females is indispensa- • Platycheirus manicatus and lookalikes. ble for resolving difficult species and indi- Dusek and Laska (1982) review the viduals. Males are mainly recognised by species with a slender tibia 1 and broad- the morphology of and the hairs and ened metatars 1. Some of these have grey bristles on legs 1 and 2. Most species have spots, and are P. albimanus lookalikes. The enlarged front tibia and/or metatars in species with yellow spots are P. manicatus the male. Recognition of the females is lookalikes, such as P. tarsalis, P. melanopsis more difficult and some keys practically and P. tatricus. The Mediterranean P. fascic- refuse to key out many females (Van der ulatus and P. cintoensis also belong to this Goot, 1981; Vockeroth, 1992) and this is group. not without reason. The present key • Platycheirus scutatus and lookalikes. aimed to include the females, but had to Recently, three species have been omit females of some species (e.g. P. nigro- described that are very similar to P. scuta- femoratus, P. groenlandicus, P. lundbecki). tus, two of which occur within the scope Some groups of lookalikes need particu- of the book: P. splendidus and P. aurolater- lar attention in the field. alis. • Platycheirus albimanus and lookalikes. The key is based on Van der Goot (1981), This group represents all species with Dusek and Laska (1982), Van der Linden greyish or silverish spots. P. albimanus is (1986), Speight and Goeldlin de Tiefenau common in many countries and hides the (1990), Vockeroth (1992), Doczkal other species in the field. (1996), Stubbs (1996), Van Steenis and • Platycheirus peltatus and lookalikes. A Goeldlin de Tiefenau (1998), Rotheray group of relatively large species who are (1998), Stubbs (2002), Stubbs and Falk very similar in morphology; reference (2002), Doczkal et al. (2002), Smit (2003), material is necessary to be certain of Nielsen (2004) and Bartsch et al (2009a). species identity. P. peltatus is the dominant species at lower altitudes. In The KEY Netherlands, it can occur en masse in the Flevopolders, 3-5 metres below sea level. At higher altitudes, P. nielseni becomes 1.a. Males › 2 more abundant (Van der Linden, 1991), 1.b. Females (identify with care, not all already occurring in the Belgian Haute species are included)-> › 47

172