The Hoverfly Fauna (Diptera, Syrphidae) from Six Years Of
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© Norwegian Journal of Entomology. 3 December 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 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 Table 1. Relative frequencies (%) of Syrphidae caught in Malaise traps from a barley crop and its forest boundary (Fo-Bo) or grass boundary (Gr-Bo) during 1992-1997. Bold: species with rank 1-3 in dominance pr year and habitat. Year 1992 1992 1993 1993 1994 1995 1995 1996 1996 1996 1997 1997 Tot. ind. Habitat Fo-Bo Crop Fo-Bo Crop Crop Gr-Bo Crop Gr-Bo Fo-Bo Crop Gr-Bo Crop Sampling period 7.5- 13.5- 5.5- 10.5- 1 6.5- 2.5- 16.5- 23.4- 23.4- 11.6- 8.4- 8.4- 29.10 2.9 3.11 20.8 8.8 12.9 25.8 11.6 15.10 15.10 11.11 11.11 Barley sown/thrashed 8.5/ 30.4/ 6.5/ 6.5/ 15.5/ 23.4/ 2.9 20.8 10.8 28.8 6.9 11.8 Baccha elongata (Fabricius, 1775) 2.0 0.2 1.1 5.3 5 Brachyopa testacea (Fallén, 1817) 15.6 2.2 17 Brachypalpus laphriformis (Fallén, 1816) 2.0 1 Cheilosia albitarsis (Meigen, 1822) 1.1 1 Cheilosia longula (Zetterstedt, 1838) 2.6 1 Cheilosia pagana (Meigen, 1822) 2.0 0.2 1.4 3 Cheilosia rufi mana Becker, 1894 ♀ 1.1 1 Cheilosia vernalis (Fallén, 1817) 2.0 1 Chrysotoxum arcuatum (Linnaeus, 1758) 0.7 0.2 2 Chrysotoxum bicinctum (Linnaeus, 1758) 1.7 0.6 0.2 1.4 6 Chrysotoxum cautum (Harris, 1776) 0.3 1 Chrysotoxum fasciolatum (De Geer, 1776) 2.0 1 Chrysotoxum festivum (Linnaeus, 1758) 1.7 0.4 2 Dasysyrphus hilaris (Zetterstedt, 1843) 2.0 0.6 3 Dasysyrphus pauxillus (Williston, 1887) 0.3 1.2 1.4 3 Dasysyrphus pinastri (De Geer, 1776) 1.7 0.7 2 Norw. J.Entomol.54,135-145 Norw. Dasysyrphus tricinctus (Fallén, 1817) 2.0 0.3 2 Dasysyrphus venustus (Meigen, 1822) 0.3 0.4 0.2 3.3 7 Didea fasciata Macquart, 1834 0.7 1 Epistrophe fl ava Doczkal & Schmid, 1994 2.0 1 Epistrophe grossulariae (Meigen, 1822) 2.0 1 Epistrophella eucroma (Kowarz, 1885) 0.3 0.2 0.7 1.1 4 Episyrphus balteatus (De Geer, 1776) 1.9 7.1 1.7 1.7 44.1 11.6 5.3 2.2 148 Eumerus fl avitarsis Zetterstedt, 1843 2.0 1 Eumerus funeralis Meigen, 1822 0.3 0.4 2 137 Eumerus strigatus (Fallén, 1817) 0.9 0.8 0.2 1.2 11 Hågvar & Nielsen: The hover fl y fauna in an organic barley fi eld y faunainanorganicbarleyfi The hoverfl Hågvar &Nielsen: 138 Table 1. continued Eupeodes ?bucculatus (Rondani, 1857) 0.3 1 Eupeodes corollae (Fabricius, 1794) 0.6 10.2 2.5 7.4 18.6 11.1 3.0 2.7 0.8 147 Eupeodes lapponicus (Zetterstedt, 1838) 0.3 0.7 2.6 3 Eupeodes latifasciatus (Macquart, 1829) 1.2 1 Eupeodes lundbecki (Soot-Ryen, 1946) 1.7 1.0 1.5 2.3 2.6 0.7 22 Eupeodes luniger (Meigen, 1822) 0.3 0.2 2 Eupeodes nitens (Zetterstedt, 1843) 0.3 0.2 2 Ferdinandea cuprea (Scopoli, 1763) 10.0 0.3 1.1 18.4 14 Helophilus pendulus (Linnaeus, 1758) 2.4 0.4 5.4 8 Melangyna lasiophthalma (Zetterstedt, 1843) 2.0 0.3 1.5 10.0 0.7 1.4 15 Melanogaster cf.