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Insect fauna of tallgrass prairies
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Introduction
This website is intended as a pictorial catalogue of the insects identified from tallgrass prairies at three sites in western Minnesota. Information presented here is based upon an ongoing research project: The effects of standard management practices on, and faunistics of native prairies: A study of the arthropods at three tallgrass prairie sites in western Minnesota. These pictures by themselves do not constitute an identification manual, in very many cases, there are one or more additional species with a similar habitus. Furthermore, not all diagnostic characters of a single species can be illustrated in one or two photographs. The purpose here is to provide a 'window' for stewards, naturalists, and interested non-specialists, to the insect fauna of the tallgrass prairies. This site will be continually updated as additional species are identified and photographs are taken. |
Study area Management practices Sampling methods Species lists Imaging techniques
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The prairie project:
Effects of standard management practices on, and faunistics of native prairies: A study of Arthropods at three tallgrass prairie sites in western Minnesota.
Beginning in mid-1995 and continuing, a project was initiated to examine the effects of standard prairie management practices on the arthropod fauna of tallgrass prairies on three sites in western Minnesota and to compile species inventory data. Research results have been, and are continuing to be published in primary scientific literature. It is somehow appropriate, after a century which has witnessed the reduction of native prairies to less than one half of one percent, that we are asking the twin questions– What portion of our inheritance of biotic diversity has been preserved, and– Is this portion being maintained? The information presented herein provides a baseline for the first of these queries.
Three sites in western Minnesota, were chosen as study areas. They are: 1. Bluestem prairie complex (Bluestem State Natural Area [SNA], Buffalo River State Park, County owned hayland, and local ranchland); 2. Felton prairie complex (Blazingstar SNA, Bicentennial Prairie, B-B ranch, County owned hayland, and leased land) and 3. Agassiz Dunes prairie complex (Agassiz Dunes SNA, Prairie Smoke SNA, and City of Fertle parkland). In the species lists, these sites are designated as B, F, and A, respectively.
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Bluestem prairie complex. There are 12 transects and 35 stations on the Bluestem prairie complex: two transects respectively on dry, mesic, and wet prairies managed by burning; two transects on hayed land and unmanaged land; and a transect each on reclaimed prairie and on prairie managed by grazing. Each transect consists of three stations except the first hayed transect which has two. At the inception of this study in 1995, only the first six transects listed above were run, each transect had five stations save the first dry transect which had six.
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Felton prairie complex. On the Felton prairie complex there are eight transects and 24 stations with two transects for each of four treatments: burned, hayed, grazed, and unmanaged prairie. Each transect consists of three stations except as follows: in 1995 there was a single, five station, transect on hayed land, two five station transects on burned lands, and a single five station transect on grazed land. The Felton site consists of mesic to dry prairie.
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Agassiz Dunes prairie complex. Agassiz Dunes prairie complex has six transects, four on lands managed by burning, and two on unmanaged prairie. Of these two, one was burned about 25 years previous, the other, in roughly the same time frame, was managed by grazing. Transects have been designated A-F, each transect again consists of three stations except as follows: in 1995 there were only four transects, three (A, B, C) on burned and the fourth (D) on unmanaged prairie with a history of burning. Each of the 1995 transects consisted of five stations.
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Historically, fire and grazing by bison were integral parts of the prairie landscape. Consequently, native prairies were a mosaic of vegetational succession stages based upon these two factors as well as local edaphic and environmental conditions. With fragmentation of the prairie landscape, each 'biotic island' of prairie must be managed. Standard management practices include burning, grazing (by cattle), and haying,. In this project, we monitored sites under each of these management regimes as well as areas not under any management plan.
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Burning. Dry, mesic and wet prairie transects at Bluestem SNA, and the A, B, C, and E transects at Agassiz Dunes SNA, and Blazingstar and Bicentennial prairies of the Felton Prairie complex were managed by burning. Burns were ideally scheduled on a four to five year rotation at a given site, however, weather conditions (moisture/wind), encroachment of woody plants, and even availability of personnel, dictated parts of these schedules.
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Haying. Two transects on the Felton prairie complex and two on the Bluestem prairie complex were managed by haying. On a few occasions, inclement weather prevented annual haying over the course of this project, such that every site was not hayed in every season from 1995 to the present. |
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Grazing. Two sites in Felton prairie complex were managed by grazing. These sites, located on the B-B ranch were subject to periodic seasonal grazing. An additional site on the Bluestem prairie complex was intermittently subjected to grazing. Because pastures are enclosed areas, and cattle prefer some plant species over others, cattle movements and grazing patterns are also important. These sites clearly show a mosaic of vegetation cover.
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No management. Six transects, two per site on the Bluestem, Felton, and Agassiz prairie complexes, respectively were not managed. At Agassiz Dunes, one of the transects had a history of grazing, another was historically managed by burning. Neither had been managed for the preceding 25 years. |
Arthropods were collected via sweep-net, pitfall trap, Malaise trap, window-pane trap and light trap. In 2003, a more efficient type of Malaise trap was used as well as Flight intercept traps. These changes enabled better collections of microhymenoptera, Diptera, and allow for some quantitative data on Lepidoptera. Sweep-net samples collect planticolous insects. Pitfall traps collect terricolous species. Malaise, Window-pane, and Flight Intercept traps are flight traps which collect insect which fly upward or drop downward, upon meeting a barrier. Light trapping by the use of a Mercury vapor light and a Black light takes advantage of the phototropism often exhibited by nocturnal insects. It is a qualitative method for sampling.
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Sweep net samples consisted of 50 sweeps with a 38 cm diameter sweep net, in a circle about each station. Samples were placed in labeled Zip-loc® bags and transported to the lab where they were transferred to Petri dishes for drying and temporary storage. Exceptions to this procedure were as follows: in 1995, two samples were taken for each station. In 1995 and the first two sampling dates of 1996, samples were taken along the transect rather than around each station. At the Agassiz Dune prairie complex, samples for all years were taken in linear transects corresponding to the dune crest, dune slope, and dune slack areas as local topography usually prevented a circumlocution of each station.
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Pitfall traps consist of two 16 oz. (4.73 cc) plastic cups counter sunk into the ground and separated by a meter length of lawn edging. Each cup contains about 4 oz. (1.2 cc) of ethylene glycol (anti-freeze). Insects travel along the barrier created by the lawn edging and are trapped in the ethylene glycol. |
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Malaise traps (1995- 2001) consist of four fine mesh panels below a conical mesh top. At the apex of the cone is an inverted funnel leading to a jar. The jar contains a killing agent (vapona). Insects, upon meeting the barrier of the panels move upward into the cone and ultimately into the jar where they are trapped and killed. In 1995 these traps were placed on the D1, M1, and W2 transects at Bluestem. From 1996- 2001, Malaise traps were placed on D2, M1, W2, and N1 transects at Bluestem, the BzS transect at Felton, and the A and D transects at Agassiz Dunes (Agassiz Dunes only through 2000). In 2002-3 a different design of Malaise trap was employed, a ‘T’ design with east/west and south facing panels below the conical funnel leading to a container of alcohol. Liquid preservation of specimens allowed for a greater diversity of recoverable groups– i.e. Diptera often are decapitated in dry samples and aerial microfauna is often not recoverable. The original style trap lent itself to the preservation of Macrohymenoptera. |
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Window-pane traps consist of a plexi-glass barrier above a tray of ethylene glycol mounted in a wooden frame. The frame is suspended between two pipes which are anchored into the ground. The frame heights are periodically adjusted so as to be at the top of the growing vegetation. From 1995-2000 these were placed on the D2, M2, W1 transects on Bluestem, on BzS and B-B1 transects at Felton, and B and D transects at Agassiz Dunes. From 1996-2000, additional Window-pane traps were placed on N1, H1 transects on Bluestem, the CCL1 and CNM1 transects at Felton, and the E and F transects at Agassiz Dunes. In 1996 and 1997 a Window-pane trap was placed on the F1 transect at Bluestem. A refined version of the Window-pane trap known as a Flight intercept trap was employed in 2003, see below.
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Berlese funnels were used in the laboratory to extract insects from soil samples. Duff, and surface soil is placed in the funnel which has a mesh screen below, and was suspended over a beaker of ethanol. The heat from the 25 watt bulb slowly dries the sample, driving the soil fauna from the sample into the beaker. We ultimately found that we were getting a good representation of soil insects via the pitfall traps which were 'countersunk' about 5 cm below the soil surface. |
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Flight intercept traps consist of a 12 x 24" aluminum pan (painted yellow) containing a dilution of ethylene glycol and ethyl alcohol. The trap is bisected along the short axis by a vertical fine mesh screen supported by poles. The trap is placed on the ground and the pan covered with wide mesh screening to prevent ground dwelling vertebrates from reaching the ethylene glycol. These traps, collect medium and small insects flying just at canopy level as well as microhymenoptera, smaller Diptera, and small Homoptera active below the vegetation canopy. |
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Light trapping consisted of attaching a Mercury vapor light and a long-wave UV light to a metal frame. A white sheet was stretched over the frame and the frame was then anchored into the ground. An additional sheet was placed on the ground below the frame. Nocturnal insects, coming to the light would alight on the suspended sheet or on the ground sheet where they were easily collected. This is a qualitative sampling method as the collector must actively determine which specimens are to be taken. |
Sampling protocol.
Beginning in May, and continuing into September usually until the first frost, transects were established on each site. At approximately two week intervals (weather permitting) sweep net samples and pitfall trap samples were taken from each station. In addition, Malaise and Window-pane trap samples were taken. Flight intercept samples were taken at one week intervals. Sweep net samples were treated as noted above. Pitfall and window-pane samples were stored in 95 % ethanol until processing. Malaise trap samples were also stored in Petri dishes.
Home Species lists Researchers Acknowledgements Imaging techniques
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Last updated:
05/07/04
Gerald M. Fauske
Collection manager, NDSIRC
NDSU
216 Hultz Hall
Fargo, ND 58105
E-Mail: Gerald.Fauske@ndsu.nodak.edu
Published by the Department of Entomology
Prospective students may schedule a visit by calling 1-800-488-NDSU.