Insect fauna of tallgrass prairies
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.
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.
The Study Area
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.
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
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.
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
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.
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.
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.
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.
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.
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.
|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.
|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
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.
|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.
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.
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.
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.
[Good web citizens, when borrowing
photographs, cite their sources]
Gerald M. Fauske
Collection manager, NDSIRC
216 Hultz Hall
Fargo, ND 58105
Published by the Department of Entomology
Prospective students may schedule a visit by calling 1-800-488-NDSU.