The Hoverfly Fauna (Diptera, Syrphidae) from Six Years Of

The hoverﬂ y fauna (Diptera, Syrphidae) from six years of Malaise trapping in an organic barley ﬁ eld and its boundary in southern Norway

Eline Benestad Hågvar & Tore R. Nielsen

Hågvar, E. B. & Nielsen, T.R. 2007. The hoverﬂ y fauna (Diptera, Syrphidae) from six years of Malaise trapping in an organic barley ﬁ eld and its boundary in southern Norway. Norw. J. Entomol. 54, 135-145.

Two Malaise traps, one in an organically grown barley crop and one in its wooded boundary, were collecting syrphids throughout the season in six successive years, 1992-1997, in southern Norway. 88 syrphid species were collected, 95 % having aphidophagous larvae. There was a considerable annual turnover rate in the species complex, and only ﬁ ve of the 88 species were caught all years. Some species dominating one year were absent in other years. The fauna from the crop and from the boundery differed: only 20-40 % of the species were common each year. The abundance of syrphids was generally higher in the crop than in the boundary, but not always the species number. The samples were female biased, indicating that female ﬂ ight behaviour makes females more vulnerable to Malaise traps than males. The study increases the present knowledge of phenology, habitat preferences and hibernation states of single species of syrphids. The main message from this study is that annual changes in the syrphid complex are considerable, both qualitatively and quantitatively. This is important to know when ecological studies on syrphid fauna are carried out for one season only.

Key words: Syrphidae, Malaise traps, species turnover, phenology, southern Norway

Eline Benestad Hågvar, Department. of Ecology and Natural Resource Management, P.O.Box 5003, Norwegian University of Life Sciences, NO-1432 Ås, Norway. E-mail: [email protected] Tore R. Nielsen, Sandvedhagen 8, NO-4318 Sandnes, Norway. E-mail: [email protected]

INTRODUCTION It is known that Malaise traps also collect syrphids In 1992-1997 a large project on biodiversity in rather effi ciently, and specimens from this family an organically managed fi eld in Ås, southern were sorted out from the same traps mentioned Norway, was conducted (Andersen et al. 1999). above. The Norwegian syrphid fauna is fairly A part of that project was the study of leaf mining well known (Nielsen 1999, 2002, 2003, 2005), fl ies (Chromatomyia fuscula (Zetterstedt)) in but permanent traps throughout the season in six barley and their parasitoids (Hågvar et al. 1998, succeeding years in crop and boundary may give Hågvar et al. 2000). To register the leaf miners, additional information on seasonal, annual and their parasitoid species and their habitat use, two sex ratio fl uctuations, and also whether a crop and Malaise traps were collecting insects from the a boundary trap in the same fi eld collect different crop and the fi eld border throughout the season species assemblages. for six years.

135 Hågvar & Nielsen: The hover ﬂ y fauna in an organic barley ﬁ eld

More traps would surely have given more boundary”, had only a narrow strip of grasses consistent results, but our results may still be with less plant diversity. valuable when comparing with. the known biology and phenology of certain species. In each of the years 1992-1997 two black Malaise traps sampled throughout the season, from April/ May to August /November. One trap was placed in MATERIAL AND METHODS the barley crop, 60 m from the boundary, the other along the forested boundary of that year’s barley The study site was a 15.5 ha organically managed crop. The boundary trap was placed between the fi eld at Ås, 30 km south of Oslo. Previously, trees in 1992, 1993 and 1996 and in the grass this fi eld was a conventional meadow, but was boundary in 1995 and 1997. In 1996, an additional transformed during 1991-1994 to an organically– trap in the grass boundary collected only early in grown fi eld with crop rotation. It had a six course the season (April – June). In 1994, no boundary crop rotation, each crop covering a rectangle of trap was used. More detailed descriptions of the about 2.5 ha. In addition to a barley crop, the other studied area and trap positions are given in Hågvar fi ve crops in the rotated fi eld were meadow, row et al. (1998). crop (beet/rape/oats/barley), green fodder (peas, oats), grass (included red clover) and rape/ryegrass. The trap had a collecting bottle with 70 % alcohol According to the rotation scheme, the location of and was emptied at least once a week. The syrphids the barley crop within the fi eld changed from year were sorted out and conserved in 70 % alcohol for to year (Hågvar et al. 1998). later identifi cation.

A total of 118 plant species were registered in Continuous weather data were available from a the fi eld boundaries, including 11 tree species station 1 km away. June-September were coldest (Andersen et al. 1999). The eastern and southern in 1993, whereas 1992 and 1994 had a warm and margins of the fi eld were surrounded by a rich dry early summer and 1997 a warm late summer. deciduous forest. A semi-natural boundary strip In 1995, June-July was very rainy (Hågvar et with grasses lay between the fi eld and the forest. al.1998). The eastern boundary, referred to as “grass boundary”, had a 4 meter broad strip with 69 plant The diversity of the syrphid complex was measured species. The southern boundary, named “forest by the Shannon-Wiener diversity index (H’):

H’= - ∑(pi • ln pi), where pi is the relative frequency 100 of species i, and by the transformed index: D= exp (H’).

80 According to Jost (2006), H’ is by itself not a

60 diversity, but an entropy, whereas D represent a true diversity, i.e. an expression of the “effective

40 number of species” in the community (MacArthur

Number of species 1965). D is thus the number of evenly distributed

20 species that is needed to obtain a diversity index similar to the one estimated for the community.

0 Both α - (each year treated separately), γ- (all 1992 1993 1994 1995 1996 1997 years lumped together) and β - (species turnover) Figure 1. Annual (columns) and cumulative indices are estimated. (line) number of Syrphidae species from Malaise The relations between the indices are:

traps during 1992-1997. The crop- and boundary H’α + H’β= H’γ trap are treated together. Dα • Dβ= Dγ

136 Norw. J. Entomol. 54, 135-145 ary 2.2 17 15.6 5.3 2.2 148 44.1 11.6 1.7 7.1 1.1 1 ♀ (Fallén, 1816) 2.0 2.0 1816) 1 (Fallén, (De Geer, 1776) (De Geer, 2.0 1 (Meigen, 1822) 2.0 1822) 2.0 1 (Meigen, (Linnaeus, 1758) 1.7 0.6 0.2 1.4 6 (Linnaeus, 1758) 0.7 0.2 2 (Meigen, 1822) 0.3 0.4 0.2 3.3 7 (Fallén, 1817) 2.0 0.3 2 (Kowarz, 1885) 0.3 0.2 0.7 1.1 4 (Williston, 1887) 0.3 1.2 1.4 3 (Linnaeus, 1758) 1.7 0.4 2 (Harris, 1776) 0.3 1 (De Geer, 1776) (De Geer, 1.9 (De Geer, 1776) (De Geer, 1.7 0.7 2 (Fallén, 1817) (Zetterstedt, 1843) 2.0 0.6 3 Zetterstedt, 1843 2.0 Zetterstedt, 1 (Meigen, 1822) 1.1 1 Becker, 1894 Becker, Meigen, 1822 (Fallén, 1817) 0.3 0.9 0.8 0.2 1.2 0.4 11 2 (Zetterstedt, 1838) 2.6 (Zetterstedt, 1 (Fallén, 1817) (Fallén, 2.0 1 (Fabricius, 1775) 2.0 0.2 1.1 5.3 5 (Meigen, 1822) 2.0 0.2 1.4 3 Doczkal & Schmid, 1994 2.0 1 Macquart, 1834 Macquart, 0.7 1 Relative frequencies (%) of Syrphidae caught in Malaise traps from a barley crop and its forest boundary (Fo-Bo) or grass bound Brachypalpus laphriformis Cheilosia albitarsis Cheilosia longula Cheilosia pagana Cheilosia rufi mana Cheilosia rufi Didea fasciata Epistrophe fl ava Epistrophe fl Epistrophe grossulariae Chrysotoxum fasciolatum Dasysyrphus pinastri Dasysyrphus venustus Epistrophella eucroma Episyrphus balteatus Cheilosia vernalis Chrysotoxum bicinctum Chrysotoxum cautum Chrysotoxum festivum Dasysyrphus hilaris Dasysyrphus pauxillus Dasysyrphus tricinctus Chrysotoxum arcuatum Eumerus fl avitarsis Eumerus fl Eumerus funeralis Eumerus strigatus (Gr-Bo) during 1992-1997. Bold: species with rank 1-3 in dominance pr year and habitat. 29.10 2.9 3.11 20.8 8.8 12.9 25.8 11.6 15.10 15.10 11.11 11.11 11.11 15.10 15.10 11.6 25.8 12.9 8.8 20.8 3.11 2.9 1. Table Year period Habitat Sampling 8.4- 8.4- sown/thrashed 11.6- 29.10 23.4- 23.4- 16.5- Barley 2.5- 6.5- Crop Gr-Bo 1 Crop Baccha elongata Fo-Bo Gr-Bo 5.5- 10.5- Crop 7.5- 13.5- 6.5/ 23.4/ 8.5/ 15.5/ 30.4/ Gr-Bo Crop Fo-Bo Crop ind. Fo-Bo Crop 1992 1993 1992 1996 1993 1994 1995 Tot. 1996 1997 1996 1997 28.8 10.8 2.9 6.9 20.8 11.8 Brachyopa testacea

137 Hågvar & Nielsen: The hover ﬂ y fauna in an organic barley ﬁ eld 1.6 55 22.2 166 0.8 44 0.8 2.7 17.6 1.4 0.4 1.4 24 14 30.4 14.1 1.4 17 1.4 13.2 18.4

4.4 11.1 11.1 2.7 3.0 0.8 147 12.2 0.2 18.4 0.2 18.6 3.6 1.4 131 9.9 11.9 8.1 2.5 7.4 10.2 3.4 0.4 3.4 0.8 6.0 0.7 10.2 7.1 11.9 11.9 0.3 1.1 4.8 3.4 1.1 0.7 18.0 10.0 0.3 0.3 1 ♀ 0.4 1 ♀ sp. (Loew, 1840) (Loew, 0.3 1 (Zetterstedt, 1843) 2.0 0.3 1.5 10.0 0.7 1.4 15 (Verrall, 1873) (Verrall, 6.0 0.3 0.7 0.2 1.4 7 (Zetterstedt, 1843) 3.4 0.4 0.2 (Zetterstedt, 1843) 0.4 0.4 1843) 2 (Zetterstedt, (Collin,1952) 2.0 1 (Fabricius, 1781) 1.7 1.5 0.7 2.4 2.6 (Linnaeus, 1758) 2.0 4.1 (Zetterstedt, 1843) 4.0 0.9 1.7 0.4 2.2 0.7 1.4 12 (Rondani, 1857) 0.3 1 (Meigen, 1830) 1.1 (Meigen, 1 (Macquart, 1829) 1.2 1 (Meigen, 1822) 6.3 1.7 (Panzer, 1804) (Panzer, 2.0 0.9 1.7 0.8 2.7 0.4 12 Nielsen, 1971 1.1 1 (Zetterstedt, 1838) 0.3 0.7 2.6 3 (Fabricius, 1794) 6.0 1.9 (Zetterstedt, 1843) 0.2 2.6 1.4 3 (Soot-Ryen, 1946) 1.7 1.0 1.5 2.3 2.6 0.7 22 (Linnaeus, 1758) 2.4 0.4 5.4 8 (Scopoli, 1763) Curran, 1927 1.7 1.4 2 (Zetterstedt, 1843) (Zetterstedt, 1843) 0.3 1.1 2 (Fabricius, 1794) 0.6 (Fabricius, 1794) Meigen, 1822 0.3 1 (Meigen, 1822) 0.3 0.2 2 (Linnaeus, 1758) 2.6 (Linnaeus, 1 (Zetterstedt, 1843) 0.3 0.2 2 Zetterstedt, 1843 0.6 1.7 1.1 2.6 0.7 6 (Linnaeus, 1758) 1.2 1 (Fabricius, 1775) (Fabricius, 0.2 1 sp. 1.7 2.9 0.4 5.3 6.7 4.0 28 4.0 6.7 5.3 0.4 2.9 1.7 sp. 0.9 2.2 2.2 1.4 9 ♀ sp. Melanostoma scalare Melanostoma Meligramma triangulifera Meliscaeva cinctella Merodon equestris Eupeodes lapponicus Eupeodes latifasciatus Eupeodes lundbecki Eupeodes luniger Eupeodes nitens Ferdinandea cuprea Helophilus pendulus Melangyna lasiophthalma Melanogaster cf. parumplicata Melanostoma mellinum Platycheirus jaerensis Table 1. continued Table Eupeodes ?bucculatus Eupeodes corollae Parasyrphus macularis Parasyrphus punctulatus Myathropa ﬂ orea Myathropa ﬂ Orthonevra geniculata Paragus (Pandasyophthalmus) Parasyrphus lineolus Parasyrphus malinellus Parasyrphus vittiger Pipiza bimaculata Pipiza noctiluca Pipiza Platycheirus albimanus Platycheirus amplus Platycheirus angustatus Platycheirus clypeatus Pipiza lugubris Pipiza luteitarsis Pipiza quadrimaculata

138 Norw. J. Entomol. 54, 135-145 115 156 1.6 21 21.4 10.8 19.3 17.6 26.6 712 2.6 14 2.6 12.2

6.7 5.3 2.2 1.4 5.3 2.2 6.7 22.0 49.7 53.3 15.4 1.9 0.2 1.5 2.7 7.1 152 7.1 2.7 1.5 0.2 1.9

1.1 5.1 3.7 8.1 57.1 32.2 13.3 57.1 32.2 0.6 9.1 37.9 15.5 2.7 2.4 1.6 2.7 2.3 2.0 2.5 1.5 2.6 2.0 2.1 2.7 2.0 22.0 2.0 0.9 0.8 0.8 0.9 8 2.0 2.8 2.8 9 ♀ ♀

(Fabricius, 1805) 0.2 0.2 1805) 1 (Fabricius, (Meigen, 1822) 0.6 2 (Linnaeus, 1758) 2.0 2.0 1758) 1 (Linnaeus, (Meigen, 1822) (Wiedemann, 1830) 2.5 2.5 13 0.4 1830) (Wiedemann, (Meigen, 1822) (Meigen, 1822 2.8 1.7 2.3 0.7 0.4 23 (Meigen, 1822) 0.6 2 Goeldlin, 1989 1.4 1 Goeldlin, 1974 0.2 1 (Linnaeus, 1758) (Stæger, 1843) (Stæger, 2.5 0.2 (Meigen, 1822)

(Linnaeus, 1758) 0.7 (Linnaeus, 1 (Linnaeus, 1758) 1.3 1.2 0.4 8.1 13 Meigen, 1822 2.0 Meigen, 1 ♀ Meigen, 1822 0.7 0.2 (Harris, 1776) (Harris, 0.2 1 (Fallén, 1816 3.6 5.3 5 (Linnaeus, 1758) 2.7 2 Osten Sacken, 1875 1.2 0.2 0.7 7.8 10 sp. (Linnaeus, 1758) (Linnaeus, 1758) 0.4 2.6 0.7 4 (Fabricius, 1805) 0.2 3.7 0.7 7 Meigen, 1822 0.7 1 Platycheirus cf. peltatus Syrphus vitripennis individuals species Xylota segnis syrphid Xylota tarda syrphid Total Total Shannon-Wiener diversity index H’ 317 84 50 533 90 38 59 481 136 135 74 39 12 21 2249 252 20 36 17 18 22 21 19 25 18 88 Syrphus torvus vespiforme Temnostoma bombylans Volucella inanis Volucella pellucens Volucella orum Xylota ﬂ Table 1. continued Table Platycheirus manicatus Platycheirus peltatus Platycheirus scambus Rhingia campestris Sericomyia silentis Sphaerophoria fatarum Sphaerophoria interrupta Sphaerophoria philantha Sphaerophoria rueppelli Sphaerophoria scripta Sphaerophoria Platycheirus cf. scutatus Sphaerophoria taeniata Sphaerophoria virgata Sphegina clunipes Syrphus ribesii

139 Hågvar & Nielsen: The hover ﬂ y fauna in an organic barley ﬁ eld

Table 2. Shannon –Wiener diversity (α ,γ and β ) indices of Syrphidae from Malaise traps in a barley ﬁ eld and its boundary. D = exp (H’). Total: the crop and boundary traps treated together. For further explanation, see material and methods

Diversity index Crop Boundary Total

Dα 7.38 9.58 9.77

Dγ 11.24 20.69 14.73

Dβ 1.50 2.15 1.50

The minimum of the Dγ is 1 if all years have with the cumulative species number through the identical species complex and the maximum is six years. In 1992, with very warm and dry June, 6 if all the 6 years are completely distinct and the complex was most specious, and 19 of the total equally weighted (Jost 2006). Effects of habitat 51 species (37 %) were never caught again. This on sex ratio was estimated by Fischer’s exact test, was the ﬁ rst year after the start of transformation two tailed (conservative test). to organical management. A less distinct turnover occurred in 1993-1997, when only 2-8 species were exclusive for one year (8-20 %). RESULTS Only 5 of the 88 species were caught all years: Annual variations in species complex Eupeodes corollae, Melanostoma mellinum, M. and specimen numbers scalare, Platycheirus clypeatus and Sphaero- phoria scripta. Different species dominated in A total of 88 syrphid species were collected during different years, but S. scripta was one of the two the six seasons (Table 1). There was considerable dominating species every year. Some of the highest species turnover from year to year. Figure 1 ranked species one year were nearly or completely illustrates the species number each year together absent other years, e.g. Platycheirus peltatus (rank 1 in 1992, absent in 1993), Syrphus ribesii (rank

Boundary 1 in 1993, absent in 1995), Episyrphus balteatus 40 Crop 1992 (rank 2 in 1995, absent in 1997) and Brachyopa 1994 testacea (rank 4 in 1996, absent all other years). Table 2 gives the diversity indices. Each year the 30 diversity was somewhat larger in the boundary

1997 than in the crop (Dα). But the considerable 1996s 1992 1995 20 1993 difference in the “total diversity” between the two Species 1996 1997 1995 1996 habitats is mainly due to the annual variations (Dγ).

1993 The species turnover is higher in the boundary, 10 representing two distinct communities over the 6

years (Dβ = 2.15). An ecological interpretation is

0 that the complex is more stable through years in 0 100 200 300 400 500 600 the crop than in its boundary. Specimens

Figure 2. Annual specimens/species relati- The year 1995 had the highest catches of specimens onships in Syrphidae from crop- and boundary in both the crop- and boundary trap (Table 1). Malaise traps in 1992-1997. No boundary trap Although the trap period varied between years in 1994, but the spring boundary trap in 1996 (Table 1), no obvious correlation was seen (1996s) is included. between number of specimens and trap period.

140 Norw. J. Entomol. 54, 135-145

1.0 Probably weather conditions and density of Boundary Crop 59 38 aphids were more important factors. The barley 135 252 0.8 was infested with aphids (mostly Rhopalosiphum 90 136 74 padi L.) all the years, with low infestations in 317 481 0.6 533 1992 and 1997 (max 11 % and 1 % of plants 50 infested, respectively) and modest infestations the 0.4 other 4 years (Andersen et al 1999). The highest 84 Proportion females infestation rate (max 36-70 % of the plants) was 0.2 noted in 1995, the same year with the highest number of syrphid specimens. 0.0 1992 1993 1994 1995 1996 1997 1996-spring Species complex in the crop and the Figure 3. Total annual sex ratio in Syrphidae boundary from Malaise traps in crop and boundary. Num- The crop trap generally had higher catches of bers above columns: total number of males + specimens than the boundary trap, but not always females. more species (Figure 2). Species dominating in the crop did not always dominate in the boundary: total had both sexes represented during the study Sphaerophoria, Platycheirus and Melanostoma period. Exceptions were Melangyna lasiophtalma were most numerous in the crop traps, which thus (n=15 females), Volucella pellucens (n=13 females) reﬂ ected their known preference (Pollard 1971, and Platycheirus cf. scutatus (n=8 females) with Stubbs & Falk 2002) for open, grassy habitats. only females. In Sphaerophoria taeniata (n= 23 Species composition in the crop and boundary males) only males are identiﬁ cable. trap differed considerably: Each year only 20-40 % of the species were found in both habitats. Of Effects of habitat on sex ratios, all years combined, the total species complex, 22 and 23 species were were indicated for the species that were rather registered exclusively from the boundary and the common in both crop and boundary: crop, respectively, through all years. Syrphus ribesii: 19 % females in boundary (n=68) and 69 % females in the crop (n=88); p=0.0042. The type of boundary obviously matters: The Eupeodes corollae: 73 % females in boundary grass boundary had generally more individuals (n= 22) and 37 % females in the crop (N=125); and species than the forest boundary (e.g. compare p<0.0001 the two 1996 boundaries), but not always higher Episyrphus balteatus: 53 % females in boundary diversity (Table 1). The Shannon-Wiener diversity (n= 68) and 57 % females in the crop (n=80); was lowest in the forest boundary in 1993 p=0.6208 (few species) and in the crop in 1995 (highest specimen numbers, but high dominance). The Phenology grass boundary in 1997 had the highest diversity Figure 4 shows male and female phenology of the (many species and low dominance), this boundary 6 species that were most numerous throughout being identical with that in 1995 and early 1996 the whole 6 years period. For each species, the (see Hågvar et al. 1998). year when it ranked highest in the two habitats combined was chosen (i.e. rank 1 in a,b and d, Sex ratios rank 2 in c and e, rank 3 in f), but the phenology Typically, more females than males were caught in is illustrated from the habitat in which it was most the traps (Figure 3). In the crop, the ratio was less numerous (Figure 4). female biased in the years with highest number of specimens (1992, 1994, 1995). The two traps give a picture apparently in accordance with the known phenology of these Nearly all species with more than 3 specimens in species (Pollard 1971):

141 Hågvar & Nielsen: The hover ﬂ y fauna in an organic barley ﬁ eld

30 a: Males 25 Platycheirus Females 20 peltatus 15 10 5 0 b: 01.05 01.06 01.07 01.08 01.09 01.10 01.11 100 Sphaerophoria 80 scripta 60 40 20 0 c: 01.05 01.06 01.07 01.08 01.09 01.10 01.11 20 Melanostoma 15 mellinum

0 d: 01.05 01.06 01.07 01.08 01.09 01.10 01.11 15 Syrphus ribesii 10

0 Number of specimens e: 01.05 01.06 01.07 01.08 01.09 01.10 01.11 40 Eupeodes 30 corollae

0 f: 01.05 01.06 01.07 01.08 01.09 01.10 01.11 20 Episyrphus 15 balteatus

0 01.0501.V 01.0601.VI 01.VII 01.0701.VIII 01.08 01.0901.IX 01.1001.X 01.1101.XI Date

Figur 4. Male and female phenology of six species dominating in Malaise traps in a particular year and habitat. a: crop 1992; b, e, f: crop 1995; c: crop 1997; d: forest boundary 1993. Dotted vertical lines: start and end of the sampling period.

142 Norw. J. Entomol. 54, 135-145

P. peltatus (Figure 4a): Broadly present from June DISCUSSION in 1992. Almost all males were caught in June, whereas females were about equally common in The main message from this study is that annual June and July. When crop data from all six years changes in the syrphid complex are considerable, are combined, 96 % of all males were caught in both qualitatively and quantitatively. This is June (n=75) compared to 55 % females (n=75). important when ecological studies on syrphid The rest was caught in July. During the six years, fauna are carried out for one season only. the only two specimens found in the boundary A reason why certain species dominating one year traps were females (1997). are absent other years can be weather conditions. E. balteatus and E. corollae, which immigrate S. scripta (Figure 4b): Dominating species in late from southern countries (Gatter & Schmid summer. 1990, Torp 1994, Speight et al. 2006) may also depend on the weather further south and the wind M. mellinum (Figure 4c): The fi gure indicates two direction. generations, but there may be two species involved (taxonomy unclear) (Speight et al. 2006). Food conditions may also infl uence the annual variations. The larval biology and habitats of the S. ribesii (Figure 4d): Appears early and late in species in Table 1 can be grouped in six main the season, hibernates as larva, emerges in late types: May and has probably two generations. - aphidophagous larvae (Baccha, Dasysyrphus, E. corollae and E. balteatus (Figure 4e and 4f): Didea, Epistrophe, Epistrophella, Episyrphus, Immigration in late summer from more southern Eupeodes, Melangyna, Melanostoma, Meli- countries in continental Europe (Gatter & Schmid gramma, Meliscaeva, Paragus, Parasyrphus, 1990, Torp 1994, Stubbs & Falk 2002), but some Pipiza, Platycheirus, Sphaerophoria, Syrphus; specimens of E. corollae can be found in spring 58 species, 2137 specimens) and may have hibernated in Norway. - larvae in nests of bumle bees (Bombus spp.) and wasps (Vespula spp.). (Volucella; 3 species, 16 The species caught early in the season (May) are specimens) given below, with fi rst collection date: - larvae in/near nests of ants (Chrysotoxum; 5 Eupeodes lapponicus (5 May); Dasysyrphus species, 12 specimens) pauxillus and Meligramma triangulifera (both - herbivorous or fungi-eating larvae (Cheilosia, 12 May); Pipiza luteitarsis (13 May); Melangyna Eumerus, Merodon; 9 species, 22 specimens) lasiophthalma (14 May); Melanostoma - larvae in dead wood (Brachyopa, Brachypalpus, mellinum and Parasyrphus macularis (both 18 Ferdinandea, Sphegina Temnostoma, Xylota; 8 May); Cheilosia pagana,Cheilosia vernalis, species, 50 specimens) Dasysyrphus venustus and Syrphus ribesii (all - saprophagous larvae in cow dung (Rhingia; 1 20 May); Eupeodes corollae, Syrphus torvus and species, 1 specimen), saprophagous larvae in Syrphus vitripennis (all 21 May); Epistrophella water (Helophilus, Melanogaster, Myathropa, eucroma, Eupeodes lundbecki and Parasyrphus Orthonevra, Sericomyia; 5 species, 12 punctulatus (all 26 May); Baccha elongata, specimens). Brachypalpus laphriformis, Eupeodes bucculatus, Epistrophe fl ava, Platycheirus clypeatus and Thus, 95 % of the specimens (n= 2249) and Rhingia campestris (all 27.May); Cheilosia 66 % of the species (n=88) had aphid-feeding rufi mana, Orthonevra geniculata and Platycheirus larvae, including the dominating species. Aphids jaerensis (all 28 May). were present on barley, but probably also on other crop and boundary plants.

143 Hågvar & Nielsen: The hover ﬂ y fauna in an organic barley ﬁ eld

The generally very common Episyrphus has been collected in early April, just after a long balteatus, Syrphus ribesii and Eupeodes corollae period of low temperatures (Nielsen, unpublished). are generalists, with number of registered prey This leads us to believe that corollae can hibernate taxa 234, 128 and 124, respectively (Gilbert as imago under favourable climatic conditions. 2005). Gilbert points out three possible ways to The earliest record in the present study was 21 be a generalist: different populations specialize May, which supports this possibility. on different food, different individuals specialize on different food or all individuals are generalists. Syrphus ribesii (Linnaeus, 1758), S. torvus Osten He suspects a higher degree of specialization in S. Sacken, 1875 and S.vitripennis Meigen, 1822 ribesii on population level than expected for this All probably hibernate as larvae, but due to some very widespread species. The genera have also early observations of S. ribesii and S. torvus some specializations: Episyrphus is best adapted occasionally also as pupae. They were fi rst to aphids on Gramineae, whereas Syrphus prefer registered on 20 and 21 May in this study. Gilbert aphids on herbs surrounding the wheat fi elds (2005) found that larvae of S. ribesii exploited both (Gilbert 2005). However, since these species are the early (May-June) and the late (July-August) rather polyphagous, food condition is probably aphid population peak, i.e. on nettle aphids in not the most important reason for their annual spring and hogweed aphids in late summer. In fl uctuations. In addition, parasitation rate may be contrast, Episyrphus balteatus exploited only the a factor that needs more investigations. late aphid period. The difference between these two species is supported by the present study Only two traps per year prevent general (Figures 4d and f). conclusions and proper statistical analyses. In addition, the Malaise trap collects selectively, as The hibernation state of other early species, most traps do. Only species and individuals fl ying like Pipiza luteitarsis, Parasyrphus macularisis up to about 1 m above ground are trapped. Thus, uncertain, but is probably the larva. They the female biased sex ratio can partly be an effect were collected fi rst time on 13 and 18 May, of males often fl ying higher up than females. respectively. Whereas syrphid males often show territorial hovering high up in the air, the females have a Some notes on some less common species from more ground level fl ight behaviour in her search the sampling area (EIS 28) are given below: for pollen, nectar and aphids. Cheilosia rufi mana Becker, 1894 Hibernation state is not known for all the species. Previously recorded from only one locality in Several of our observations support present Norway (AK, Bærum: Ostøya; Nielsen 1999). An assumptions on the life cycle of certain species: early summer species. In our study registered 18 May from the boundary. Melangyna lasiophthalma (Zetterstedt, 1843) All specimens (females) except 2 were caught from Chrysotoxum cautum (Harris, 1776) both boundaries in May. This is in accordance Another early summer species, known from with its biology since the species hibernates as the Oslofi ord area (Nielsen 1999). In our study pupa (and probably also other early species of registered 11 June from the crop. this genus) (P. Láska pers. comm.). It is a spring species that emerges in April/May and forage on Epistrophe fl ava Doczkal & Schmid, 1994 pollen from Salix and Corylus avellana, which Known from seven localities in eastern Norway were present in the boundaries in this study. (Nielsen 1999, 2005). In our study registered 27 May from the boundary. Eupeodes corollae (Fabricius, 1794) Along the coast of SW Norway, a female corollae

144 Norw. J. Entomol. 54, 135-145

Platycheirus jaerensis Nielsen, 1971 ISSN 0177-7424. In southern Norway the imago is on wings from Gilbert, F. 2005: Syrphid aphidophagous predators in mid May to late June. An aphidophagous species, a food-web context. Eur. J. Entomol.102, 325-333. and the female has been observed ovipositing on Hågvar, E.B., Hofsvang, T., Trandem, N. & the underside of Vaccinium uliginosum leaves Sæterbø, K.G. 1998. Six-year Malaise trapping of the leaf miner Chromatomyia fuscula (Diptera: (Nielsen, unpublished). Agromyzidae) and its chalcidoid parasitoid complex In our study registered on 4 June from the in a barley fi eld and its boundary. Eur. J. Entomol. boundary. 95, 529-543. Hågvar, E.B., Trandem, N. & Hofsvang, T. 2000. Leaf miners and their parasitoids were collected Phenology and sex ratio of the parasitoids of a from the same traps as the syrphids (Hågvar et al. cereal leaf miner Chromatomyia fuscula (Diptera: 1998). However, populations of the leaf miners/ Agromyzidae). Eur. J. Entomol. 97, 339-346. parasitoids and the aphids/syrphids did not show Jost, L. 2006: Entropy and diversity. Oikos 113:2, parallel annual fl uctuations. For instance, the crop 363-375. trap of 1995 had the lowest specimen number MacArthur, R.H. 1965: Patterns of species diversity. of parasitoids but the highest of syrphids of all Biological Reviews of the Cambridge Philosophical Society 40, 510-533. crop traps during the six seasons. The leaf miner Nielsen, T.R. 1999. Check-list and distribution maps parasitoid complex was most specious in 1997 of Norwegian Hoverfl ies, with description of compared with 1992 as the most specious for the Platycheirus laskai nov.sp. (Diptera, Syrphidae). syrphids. Both adult leaf miner parasitoids and NINA Fagrapport 035, 1- 99. Trondheim. ISBN 82- syrphids eat pollen, whereas their larvae depend 426-1004-5. on very different prey: hidden leaf miner larvae Nielsen, T. R. 2002. Additions to the Norwegian or pupae inside the leaves and freeliving aphids, Hoverfl y fauna (Diptera, Syrphidae). Norw. J. respectively. Prey abundance certainly matters: Entomol. 49, 18. the number of leaf miner parasitoids in the traps Nielsen, T.R. 2003. Description of Eupeodes biciki correlated with the number of adult leaf miners spec. nov. (Diptera, Syrphidae) from northern (Hågvar et al. 1998), whereas the syrphid number Norway. Norw. J. Entomol. 50, 99-103. Nielsen, T.R. 2005. Additions and a correction to the was highest in the year with maximum aphid Norwegian Hoverfl y fauna (Diptera, Syrphidae). infestation. Norw. J. Entomol. 52, 139-144. Pollard, E. 1971. Hedges. VI. Habitat diversity and Acknowledgements: We would like to thank crop pests: A study of Brevicoryne brassicae and its Pavel Láska, Olomouc, Czech Republic for syrphid predators. J. appl. Ecol. 8, 751-780. valuable information on the overwintering of Speight, M., Castella, E., Sarthou, J.P. & Montell. C. Melangyna lasiophthalma. 2006. Syrph the Net on CD – Issue 5. The database of European Syrphidae. Syrph the Net Publications, Dublin. ISSN 1649-1017. Stubbs. A. & Falk, S.J. 2002. British hoverfl ies: an illustrated identifi cation guide, 2nd edition. Br. Ent. Nat. Hist. Soc., London, 469 pp. REFERENCES Torp, E. 1994. Danmarks Svirrefl uer (Diptera: Syrphidae). Danmarks Dyreliv 6, Apollo Books, Andersen, A., Elen, O., Hågvar, E.B. & Sjursen, Stenstrup. H. 1999. Biologisk mangfold ved omlegging til økologisk landbruk. Skadedyr, nyttedyr, sjuk- Received 13 September 2007, dommer og ugrasutvikling. Rapport 10/99, accepted 15 November 2007 Planteforsk. 20 pp ISBN 82-479-0150-1 Gatter, W. & Schmid, U. 1990. Wanderungen der Schwebfl iegen (Diptera, Syrphidae) am Randecker Maar. Spixiana, Supplementband 15, München.

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