Seasonal Activity of Adult, Ground-Occurring Beetles (Coleoptera)

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The University of Notre Dame
Seasonal Activity of Adult, Ground-Occurring Beetles (Coleoptera) in Forests of Northeastern
Wisconsin and the Upper Peninsula of Michigan
Author(s): Shahla M. Werner and Kenneth F. Raffa
Source: American Midland Naturalist, Vol. 149, No. 1 (Jan., 2003), pp. 121-133
Published by: The University of Notre Dame
Stable URL: http://www.jstor.org/stable/3083179
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Am. Midi. Nat. 149:121-133
Seasonal Activity of Adult, Ground-occurring Beetles
in Forests of Northeastern Wisconsin and the
(Coleoptera)
Peninsula of
Upper Michigan
SHAHLA M. WERNER1 AND KENNETH F. RAFFA
Departmento f EntomologyU, niversityo f Wisconsin,M adison 53706
ABSTRACT.-Seasonaal ctivity of 24 species of ground-occurring, forest Coleoptera in
northern Wisconsin and the Upper Peninsula of Michigan was assessed using pitfall traps
during the spring and summer of 1996 and 1997. Overall, species richness, abundance and
diversity remained relatively constant throughout the season, although species composition
varied considerably. Trap catch of seven species was greatest from early May to late June:
Calosomaf rigidum Kirby, Carabusn emoralisM iiller, Platynus decentis( Say), Pterostichusa dstrictus
Eschscholtz, P mutus (Say), P pensylvanicusL eConte and Sphaeroderusle conteiD ejean. Two
species, Carabuss ylvosusS ay and Nicrophoruss ayi Laporte, showed both early and late peaks in
trap catch. Trap catch of eight species was greatest from early July to late August: Calathus
ingratus Dejean, Synuchusi mpunctatus( Say), Pterostichusm elanarius (Illiger), Pterostichust ristis
(Dejean), Geotrupesb ayliJ ekel, Nicrophorusd efodiensM annerheim, N. tomentosusW eber and
Oiceoptoman oveboracensisF orster. Implications for studies that assess impacts of forest
management practices on beetle biodiversity are discussed.
INTRODUCTION
A diverse fauna of Coleoptera inhabits the ground layer of forest ecosystems. These
beetles contribute to a number of ecosystem processes, particularly predation, saprophagy
and fungivory. Carabidae comprise one of the most abundant and diverse groups in this
fauna (Spence and Niemela, 1994; Werner and Raffa, 2000). Carabids are often univoltine,
nocturnal and predaceous (Thiele, 1977; Hengeveld, 1980; Ovaska and Smith, 1988;
Sergeyeva and Gryuntal, 1990; Larochelle, 1990; Digweed, 1993, 1994; Currie and Digweed,
1996), although some exceptions have been noted (ohnson and Cameron, 1969).
Geotrupidae and Silphidae contain approximately 100 North American species and,
likewise, often occur on the ground of forest ecosystems (Howden, 1955; Anderson, 1985).
Many silphids and geotrupids feed on carrion as larvae and adults, and are integral to
nutrient cycling (Howden, 1955; Anderson, 1985).
Understanding seasonal patterns of ground-occurring Coleoptera is of interest for several
reasons. First, seasonal information can be used to determine optimal sampling periods
when studying biodiversity and habitat associations. Second, carabids are often used in
biological control, and seasonal information is needed to understand their co-occurrence
with pest species (Suenaga and Hamamura, 2001). Third, seasonal information can be used
to evaluate potential impacts of non-native fauna (Niemeli et al., 1997), which can displace
native congeners. Such displacement may be less likely where temporal separation exists.
Several studies have investigated seasonal activity of ground-occurring Coleoptera in
forests (Barlow, 1970;Johnson, 1975; Bousquet and Pilon, 1977; Liebherr and Mahar, 1979;
Bousquet and Pilon, 1980; Shubek et al., 1981; Loreau, 1985; Epstein and Kuhlman, 1990;
Trumbo, 1990; Niemela et al., 1992; Beninger; 1994; Lingafelter, 1995) and agroecosystems
1 Present address: 345 Russell Laboratory, 1630 Linden Drive, Madison, Wisconsin 53706. Telephone
[phone]; FAX [phone]; e-mail: [email protected]
121
122 THE AMERICANM IDLAND NATURALIST 149(1)
(Pavuk et al., 1997; Suenaga and Hamamura, 2001). However, our knowledge of seasonal
distribution of forest species in the Great Lakes region is limited.
This study was part of an evaluation of the biodiversity of ground-occurring beetles in
forested habitats that compared species richness, abundance and diversity among hemlock
and hardwood forest sites undergoing various management regimes (Werner and Raffa,
2000). The specific focus of the current research is to: (1) characterize seasonal occurrence
and between-year variability of common ground-occurring Coleoptera in northern forests
and (2) determine the seasonal duration required to accurately sample the species richness,
abundance and diversity of Coleoptera common to different forest habitats of the region.
STUDY AREA AND METHODS
Adult ground-occurring Coleoptera were sampled in 23 forest sites in northern Wisconsin
and Upper Peninsula Michigan. Study sites were located from 45?41' to 46?18' north
latitude, and from 88059' to 89044' west longitude in Forest, Oneida and Vilas counties in
Wisconsin and in Gogebic County, Michigan (Werner and Raffa, 2000). Altitude ranged
from 486-538 m at the sites. Areas with relatively uniform soil and vegetation characteristics
were selected using ecological classification systems of the region (Coffman et al., 1983;
Kotar et al., 1988). Dominant tree species are sugar maple (Acer saccharumM arsh.) and
eastern hemlock (Tsuga canadensis [L.] Carriere). The sites are classified as Acer-Tsuga-
Dryopteris or Acer-Tsuga-Maianthemum (Kotar et al., 1988). These sites experienced a variety of
management regimes (Werner and Raffa, 2000).
Climate of this region is characterized by monthly temperatures ranging from 12 C to
19 C, annual mean precipitation of about 85 cm (National Oceanic and Atmospheric
Administration, 1996) and an annual frost-free period of less than 100 d (Albert et al., 1986).
Climatological data from Eagle River,W isconsin, near the geographic center of the 23 study
sites, were obtained from the National Climatic Data Center (National Oceanic and
Atmospheric Administration, 1996; National Oceanic and Atmospheric Administration,
1997). Degree-days were calculated by recording one cooling degree-day for each whole
degree of mean temperature above a threshold of 10 C, which has been previously
considered to be representative of many insect species (Pruess, 1983). Although more
complex methods of calculating degree-days are available, Roltsch et al. (1999) found the
historical averaging method to be comparable to these methods from April to September,
which encompasses the duration of the current study.
Following the methods of previous investigators, we used pitfall traps to characterize the
seasonal distribution of ground-occurring Coleoptera (e.g., Barlow, 1970; Bousquet and
Pilon, 1977; Liebherr and Mahar, 1979; Loreau, 1985; Epstein and Kuhlman, 1990; Trumbo,
1990; Niemela et al., 1992; Beninger, 1994; Lingafelter, 1995; Pavuk et al., 1997). Pitfall traps
may be influenced by several factors, including insect size (Luff, 1975; Spence and Niemela,
1994), activity (Greenslade, 1964), habitat structure (Greenslade, 1964; Melbourne, 1999)
construction material (Luff, 1975) and season (Baars, 1979). Therefore, results must be
interpreted with caution, recognizing that trap catch reflects an interaction of activity and
abundance rather than actual abundance (Greenslade, 1964). Pitfall traps consisted of two
pairs of 625 ml plastic cups connected by a rectangular piece of garden edging, which acted
as a barrier to increase trap surface area (Luff, 1975; Durkis and Reeves, 1982; Holland and
Smith, 1999). The cups in each pair were placed within one another to minimize trap
disturbance during sampling (Lenski, 1982). Traps were arranged within a 250 X 250 m area
within each of the 23 forest sties (Werner and Raffa, 2000). Four ounces of propylene glycol
(Sierra brand, Safe Brands Corp., Omaha NB)/water solution (1:1) were added to each
trap. In 1996 each site contained eight barrier pitfall traps, but subsequent analysis
2003 WERNER& RAFFAB: EETLEA CTIVITY 123
1300- 14
1200 - 1996 Precipitation
i1o0, - =~ 1997 Precipitation - 12
FIG1. 1996 Degree Days
o 1000- v 1997 Degree Days 800 - - 1100
i 900 -
800-
-8
700 -
6006 -
yieldeeihdt colcton etee 1 ayan 0 ugst196 ad-6 o
o 500 -
-
o 400- -4
300 -
200- -2
100 -
April May June July August
FIG.1 .-Accumulated cooling degree-days( C) and total precipitation (cm) for 1996 and 1997.
Degree-dayd ata are from Eagle Riverw eathers tation (45055'N,8 9?15'W).D egree-daysc alculatedb y
averagingd aily maximuma nd minimum temperaturesm inus a low thresholdo f 10 C, beginning on
January1 (NationalO ceanic and AtmosphericA dministration1, 996, 1997)
demonstrated that only four traps were needed to characterize ground-dwelling Coleoptera
of the region (Werner and Raffa, 2000). Therefore, each site contained four traps in 1997,
and only the traps from the same four positions were used to calculate relative activity-
abundance for 1996 and 1997.
Traps were left in the field continuously and sampled approximately every 12 d; This
yielded eight collections between 18 May and 30 August 1996, and nine collections between
9 May and 31 August 1997. Differences in initial collecting dates between years are due to
leap year in 1996, and earlier initiation of sampling in 1997. However, these differences did
not significantly affect degree-day accumulation, due to the cool climate of the study region
(see Fig. 1, Results).
Beetles were identified as described in Werner and Raffa (2000). Because Carabidae
dominated trap catch in 1996 (staphylinids <3 mm in length were excluded due to
taxonomic difficulties), only this family was evaluated in 1997. Voucher specimens were
deposited at the UW-Madison Insect Research Collection (IRC). Seasonal trends of
abundantly obtained species (>200 individuals) were assessed by averaging the number of
beetles obtained among the 23 sites for each collection in 1996 and 1997. Pitfall traps
occasionally caught small mammals, and these were preserved and identified by Mitch
Bergeson (UW Madison), as these data may be relevant to seasonal occurrence of carrion
beetles.
Overall species richness, trap catch and diversity of all adult, ground-occurring
Coleoptera obtained were compared among early, middle and late seasonal periods.
Collection dates were pooled and designated as early (10 May-18June), middle (19June-24
July) or late (25July-30 August) for purposes of this analysis. Mean species richness and trap
catch for each period were compared using a one-way ANOVA (SAS Institute, 1989). A
TABLE 1.-Mean (+SE) catch of the most abundant (>200 individuals) Coleoptera in pitfall traps in 23 forested sites during May-August 1996
Mean (+SE) Coleoptera/Collection
Species Total 5/26-6/5 6/6-6/17 6/18-6/29 6/30-7/11 7/12-7/23 7/24-8/4 8/5-8/19 8/20-8/30
Carabidae
Agonum retractum LeConte 1147 1.7 (0.3) 4.6 (1.0) 11.0 (2.7) 14.2 (3.8) 8.0 (1.8) 4.0 (0.9) 2.5 (0.7) 1.6 (0.3)
Calathus ingratus Dejean 367 0.2 (0.1) 0.2 (0.1) 1.7 (0.4) 2.8 (0.5) 3.0 (0.5) 2.9 (0.6) 3.3 (0.6) 1.8 (0.4)
Calosoma frigidum Kirby 518 0.3 (0.1) 12.5 (4.0) 5.4 (1.5) 3.0 (1.0) 1.0 (0.3) 0.1 (0.1) 0.1 (0.1) 0.0 (0.0)
Carabus nemoralis Muller 657 13.9 (5.8) 7.2 (2.8) 3.3 (0.9) 2.7 (1.1) 0.4 (0.2) 0.2 (0.1) 0.2 (0.1) 0.9 (0.5)
C. sylvosus Say 577 1.7 (0.6) 2.3 (0.7) 1.8 (0.9) 0.3 (0.2) 0.1 (0.1) 1.5 (0.4) 7.9 (2.1) 9.2 (2.6)
Cymindis cribicollis Dejean 148 0.3 (0.2) 0.1 (0.1) 0.4 (0.2) 0.7 (0.2) 0.7 (0.2) 0.6 (0.2) 1.5 (0.3) 2.0 (0.4)
Harpalus fulvilabris Mannerheim 126 0.7 (0.2) 1.0 (0.3) 0.8 (0.2) 0.8 (0.2) 0.4 (0.2) 0.7 (0.2) 0.6 (0.2) 0.6 (0.2) ?_t
Myas cyanaescens Dejean 366 0.1 (0.1) 1.0 (0.2) 2.6 (0.6) 5.8 (1.2) 2.8 (0.5) 1.1 (0.3) 1.7 (0.4) 0.7 (0.2)
Platynus decentis (Say) 2091 15.0 (1.9) 20.3 (2.3) 22.6 (2.8) 23.9 (2.5) 5.2 (0.9) 0.9 (0.2) 1.4 (0.5) 1.3 (0.2)
Pterostichus adstrictus Eschscholtz 1033 11.1 (2.7) 14.5 (3.1) 9.5 (2.0) 7.0 (1.0) 0.9 (0.2) 0.7 (0.2) 0.7 (0.2) 0.5 (0.2) z
P. coracinus (Newman) 4976 3.3 (0.6) 23.8 (4.1) 31.1 (4.6) 44.2 (8.5) 28.7 (4.6) 20.9 (4.2) 44.1 (10.3) 20.0 (5.2)
P melanarius (Illiger) 3121 5.8 (3.5) 6.1 (3.4) 5.7 (2.2) 12.8 (8.4) 21.0 (15.5) 23.3 (18.1) 39.6 (26.3) 21.3 (13.4) z
P mutus (Say) 91 0.0 (0.0) 1.2 (0.3) 1.2 (0.5) 0.3 (0.1) 0.0 (0.0) 0.0 (0.0) 0.0 (0.0) 0.0 (0.0) z
H
P pensylvanicus LeConte 2093 32.4 (4.1) 23.4 (3.7) 15.7 (2.6) 13.6 (2.1) 3.0 (0.5) 1.3 (0.3) 0.8 (0.2) 1.6 (0.6) CZ
P tristis (Dejean) 353 0.1 (0.1) 0.9 (0.3) 0.7 (0.2) 3.3 (0.5) 2.1 (0.5) 3.1 (0.6) 3.6 (0.6) 1.6 (0.4)
Sphaeroderus lecontei Dejean 424 7.6 (1.0) 1.8 (0.3) 2.7 (0.5) 1.7 (0.3) 1.4 (0.2) 0.1 (0.1) 0.2 (0.1) 0.4 (0.1) H
Synuchus impunctatus (Say) 2981 0.0 (0.0) 0.0 (0.0) 0.1 (0.1) 3.5 (0.9) 12.1 (2.4) 27.2 (4.8) 49.0 (8.3) 37.7 (6.8)
Geotrupidae
Geotrupes bayliJekel 1429 0.0 (0.0) 0.0 (0.0) 1.0 (0.3) 2.3 (0.8) 3.3 (0.7) 11.4 (3.3) 25.5 (5.1) 18.6 (4.3)
Silphidae
Necrophilaa mericana( Linneaus) 465 0.2 (0.1) 7.9 (5.0) 2.4 (1.0) 6.5 (4.0) 0.9 (0.3) 0.3 (0.2) 1.0 (0.2) 1.1 (0.4)
Nicrophorusd efodiensM annerheim 10,066 0.4 (0.2) 17.0 (4.2) 44.2 (11.9) 120.0 (16.0) 58.9 (7.5) 48.9 (8.6) 105.4 (12.7) 43.0 (5.0)
N. orbicollis Say 245 0.0 (0.0) 0.8 (0.2) 1.0 (0.3) 4.7 (1.1) 1.9 (0.5) 1.1 (0.3) 0.7 (0.2) 0.4 (0.1)
N. sayi Laporte 1761 4.4 (1.9) 15.4 (3.5) 13.0 (2.9) 17.6 (3.0) 4.1 (0.9) 2.9 (0.6) 5.0 (1.2) 14.1 (3.2)
N. tomentosus Weber 617 0.0 (0.0) 0.0 (0.0) 0.0 (0.0) 0.0 (0.0) 0.3 (0.1) 1.0 (0.5) 11.4 (2.2) 14.2 (2.4)
Oiceoptoma noveoboracensis Forster 647 0.0 (0.0) 0.0 (0.0) 0.0 (0.0) 0.0 (0.0) 0.0 (0.0) 0.7 (0.3) 18.1 (5.1) 9.4 (3.7)
TABLE 1.-Continued
1997
Mean (?-SE) Coleoptera/Collection
Species Total 5/10-5/26 5/27-6/6 6/7-6/18 6/19-6/30 7/1-7/12 7/13-7/24 7/25-8/5 8/6-8/20 8/21-8/31
Carabidae
Agonum retractumL eConte 1619 1.0 (0.3) 1.8 (0.4) 3.7 (0.6) 12.7 (2.2) 27.3 (5.3) 16.3 (3.6) 3.6 (0.7) 2.7 (1.1) 1.5 (0.4)
Calathusi ngratusD ejean 558 0.1 (0. 1) 0.2 (0.1) 1.0 (0.3) 4.2 (1.0) 4.9 (1.0) 4.7 (1.0) 4.5 (1. 1) 3.3 (0.7) 1.3 (0.3)
Calosomafr igidum Kirby 1503 0.0 (0.0) 0.7 (0.2) 44.3 (27.3) 19.3 (6.6) 0.6 (0.2) 0.2 (0. 1) 0.1 (0. 1) 0.1 (0.1) 0.1 (0. 1)
Carabusn emoralisM uAller 678 3.1 (1.2) 13.9 (6.1) 8.4 (3.4) 3.0 (1.3) 0.4 (0.2) 0.1 (0.1) 0.0 (0.0) 0.1 (0. 1) 0.6 (0.3)
C. sylvosusS ay 487 0.6 (0.2) 2.9 (0.9) 2.3 (0.7) 0.8 (0.3) 0.1 (0.1) 0.1 (0. 1) 1.3 (0.3) 6.3 (1.7) 6.9 (1.9)
Cymindisc ribicollisD ejean 348 0.1 (0. 1) 0.1 (0. 1) 0.1 (0. 1) 1.3 (0.3) 0.9 (0.3) 2.5 (0.4) 3.8 (0.5) 3.0 (0.6) 3.9 (0.6)
Harpalusf ulvilabris Mannerheim 178 0.0 (0.0) 1.2 (0.4) 0.7 (0.4) 1.5 (0.4) 0.3 (0. 1) 1.0 (0.3) 1.2 (0.3) 1.1 (0.4) 0.7 (0.3)
Myas cyanaescenDs ejean 840 0.0 (0.0) 0.1 (0. 1) 1.6 (0.4) 8.2 (1.3) 3.5 (0.9) 3.5 (0.7) 8.6 (5.1) 6.3 (2.9) 4.8 (1.7)
Platynus decentis( Say) 2314 11.1 (1.6) 16.0 (2.0) 19.7 (2.4) 27.3 (2.4) 17.3 (2.9) 6.5 (1.2) 1.3 (0.2) 1.0 (0.3) 0.5 (0.2)
Pterostichusa dstrictus Eschscholtz 1536 13.7 (2.7) 20.4 (6.0) 16.1 (4.1) 9.7 (1.6) 3.4 (0.6) 1.7 (0.3) 0.5 (0.2) 0.4 (0.1) 0.8 (0.2)
P coracinus( Newman) 4356 1.6 (0.5) 8.0 (1.3) 31.2 (4.3) 40.7 (6.2) 20.7 (3.3) 30.0 (4.6) 26.6 (5.5) 21.0 (4.5) 9.7 (1.9)
P melanarius (Illger) 2189 4.9 (4.4) 5.6 (4.3) 5.9 (2.5) 10.3 (4.7) 6.1 (3.8) 16.7 (10.8) 20.5 (11.3) 17.6 (7.2) 7.5 (4.0)
P mutus (Say) 151 0.2 (0.1) 1.7 (0.3) 2.6 (0.5) 1.2 (0.3) 0.7 (0.2) 0.2 (0. 1) 0.0 (0.0) 0.0 (0.0) 0.1 (0. 1)
P pensylvanicusL eConte 3257 17.4 (1.5) 41.0 (4.5) 30.6 (3.9) 30.7 (3.7) 11.5 (1.9) 7.3 (1.0) 1.4 (0.2) 0. 7 (0.2) 0.9 (0.2)
P tristis (Dejean) 235 0.0 (0.0) 0.4 (0.2) 1.0 (0.3) 2.0 (0.4) 1.0 (0.2) 3.0 (0.7) 1.5 (0.3) 0.8 (0.3) 0.4 (0.2)
Sphaeroderulse conteiD ejean 539 5.2 (0.5) 8.2 (1.2) 4.3 (0.7) 2.4 (0.5) 2.3 (0.5) 0.3 (0. 1) 0.1 (0. 1) 0.1 (0.1) 0.6 (0.2)
Synuchusi mpunctatus( Say) 4978 0.0 (0.0) 0.0 (0.0) 0.0 (0.0) 0.5 (0.2) 6.5 (2.0) 37.1 (8.6) 62.1 (9.1) 66.3 (10.0) 44.0 (5.0)
126 THE AMERICAMN IDLANDN ATURALIST 149(1)
Mann-Whitney test (SAS Institute, 1989) was used to detect significant differences in species
richness or trap catch among these periods. The Shannon-Weiner (H'; Shannon and
Weaver, 1949) and Simpson (D; Simpson, 1949) indices were used to compare species
diversity among early, middle and late sampling periods. Diversity indices were calculated
using methods described by Magurran (1988).
RESULTS
The sites experienced similar temperatures between years, especially during the periods
when most beetles were caught (Fig. 1). 1997 was somewhat cooler earlier in the season than
1996, with fewer degree-days accumulating in April and May. However, by June, temper-
atures increased rapidly to the point that degree-day accumulation was similar to that of
1996. Total precipitation was also similar between years (Fig. 1).
There was high consistency between the two years in the seasonal activity of most species
(Table 1). Even when total trap catch of a particular species differed between years, the
relative seasonal distribution was usually not affected (e.g., Calosomafr igidum and Pterosticus
pensylvanicus,T able 1). However some species showed less consistent patterns. For example,
Myas cyanescensD ejean and P. coracinus( Newman) showed two peaks in one year, but not in
the other (Table 1).
Several species were collected primarily during the early- and or mid-portion of the
season. For example, 80% and 97% of Calosomafr igidum were obtained between mid-June
and earlyJ uly in 1996 and 1997, respectively (Table 1). Similarly, 73% of all Carabusn emoralis
were obtained during the first 3 wk in June, during both years (Table 1). Other species that
occurred primarily in the early summer included Platynus decentis, Pterostichus adstrictus, P
mutus, P pensylvanicus and Sphaeroderus lecontei (Table 1). Many of these species were
obtained in greatest abundance over the first four or five collection periods, and then
decreased dramatically.
Agonum retractum LeConte and Nicrophorus orbicolllis Say were the only two species which
peaked in midseason, i.e., the first two weeks of July (Table 1). Several other species were
most abundant from mid to late summer, including Calathus ingratus, Synuchus impunctatus,
Pterostichus melanarius, P tristis, Geotrupes bayli, N. defodiens, N. tomentosus and Oiceoptoma
noveboracensi(sT able 1). Adults of some of these species were completely absent in the first
few collections.
Two species, Carabus sylvosus (Carabidae) and Nicrophorus sayi, (Silphidae), showed
bimodal patterns of trap catch. Carabuss ylvosuss howed a much higher peak in the late than
in the early season during both years (Table 1). In contrast, N. sayi showed peaks of similar
magnitude in early and late summer (Table la). The trap catch of these species in the final
collection suggests that substantial numbers were active after the conclusion of the sampling
period. The remaining species, Harpalus fulvilabris Mannerheim, Myas cyanescens, Pterostichus
coracinusa nd Necrophilaa mericanae xhibited highly erratic fluctuations across the sampling
period (Table 1).
Species richness of adult, ground-occurring Coleoptera was greatest during the early and
middle sampling periods (Table 2). However, this difference was only significant for carabids
in 1996. Total trap catch of ground-occurring beetles did not vary significantly throughout
the season (Table 2).
Shannon diversity (H'), Shannon evenness and Simpson diversity (D) index values of
adult carabids were higher during the early and middle than in the late portions of the
season during both years (Table 3). Shannon diversity index values for all Coleoptera
obtained in 1996 were similarly higher during early and middle collection periods than in
the late collection period (Table 3). However, Shannon evenness and Simpson's diversity
TABLE 2.-Seasonal patterns in species richness and trap catch of adult ground-occurring beetles in forest sites in 1996-1997
1996 Carabidae 1997 Carabidae 1996 Coleoptera
Collection Period Mean (?sE) species Mean (+SE) abundance Mean (?SE) species Mean (?SE) abundance Mean (?SE) species Mean (?SE) abundance
Early1 34.5 + 1.5 a 2576.5 + 327.5 27.0 ? 4.5 2765.0 + 773.5 76.0 + 7.0 3332.0 ? 789.0
Middle2 32.0 ? 1.2 a 2740.0 ? 348.3 31.0 + 1.2 3218.0 + 465.9 89.3 + 3.8 5283.7 ? 1038.5
Late3 26.3 + 2.0 b 2692.3 + 492.9 23.3 + 1.5 2228.7 ? 500.1 74.7 + 6.0 5643.7 ? 1232.9
F (P > F) 6.11 (0.05) 0.03 (0.97) 1.85 (0.24) 0.69 (0.54) 2.34 (0.19) 1.04 (0.42)
1
Includes collections that occurred between 5/26-6/17 in 1996 and 5/10-6/18 in 1997
2 Includes collections that occurred between 6/18-7/23 in 1996 and 6/19-7/24 in 1997
3 Includes collections that occurred between 7/24-8/30 in 1996 and 7/25-8/31 in 1997
128 THE AMERICAMN IDLANDN ATURALIST 149(1)
TABL3E. -Seasonal variation in evenness and diversity indices of ground-occurring beetles in forested
sites in 1996-1997
1996 Carabidae 1997 Carabidae 1996 Coleoptera
Shannon's Shannon's Shannon's
Collection Period H' evenness D H' evenness D H' evenness D
Early' 2.31 0.61 7.48 2.27 0.62 7.37 2.79 0.60 11.06
Middle2 2.35 0.63 6.97 2.41 0.66 8.49 2.66 0.54 6.82
Late3 1.83 0.52 4.42 1.76 0.53 3.53 2.55 0.55 7.51
1
Includes collections that occurred between 5/26-6/17 in 1996 and 5/10-6/18 in 1997
2 Includes collections that occurred between 6/18-7/23 in 1996 and 6/19-7/24 in 1997
3
Includes collections that occurred between 7/24-8/30 in 1996 and 7/25-8/31 in 1997
were higher during the early and late than they were during the middle collection period
when all beetle families were considered (Table 3).
Twelve species of small mammals representing 564 individuals were obtained in 1996
(Table 4). All six of the most commonly caught species (>20 individuals/season), were
obtained in higher numbers during the last four collections than during the first half of the
season. This coincides with the period when most carrion beetles (i.e., Silphids and
Geotrupids) that feed on these species were also collected (Table 1).
DISCUSSION
Previous work has shown that seasonal patterns of ground-occurring beetles are
influenced by a variety of factors, including prey availability (Goulet, 1974; Colkesen and
Sekeroglu, 1989; Holloway and Schnell, 1997; Suenaga and Hamamura, 2001; Smith and
Merrick, 2001), breeding activity (Rivard, 1964; Goulet, 1974; Thiele, 1977; Loreau, 1985;
Bousquet, 1986; Niemela et al., 1992), interspecific competition (Trumbo, 1990; Trumbo
and Thomas, 1998) and microhabitat parameters such as soil moisture (Epstein and
Kuhlman, 1990; Niemela et al., 1992), temperature (Trumbo, 1990; Honek, 1997) and
humidity (Colkesen and Sekeroglu, 1989).
Carabids include spring breeders that overwinter as adults and become active as soon as
the snow melts and fall breeders that overwinter as larvae (Rivard, 1964; Thiele, 1977). In
addition, several species have bimodal seasonal peaks, reflecting breeding activity in the
spring and a (usually less pronounced) fall activity peak, in which the new generation
searches for prey to increase fat reserves needed for overwintering (Goulet, 1974). Our data
are similar to studies done elsewhere which show most carabids have highest trap catch early
in the season (Epstein and Kuhlman, 1990; Niemela et al., 1992). It has been hypothesized
that more spring breeders occur in northern regions to ensure that offspring have adequate
time to develop before winter (Anderson, 1984; Loreau, 1985; Niemela et al., 1992). The
bimodal seasonal distributions of Carabus sylvosus and Nicrophorus sayi have not been
documented in previous studies. Previously reported bimodal activity peaks for Platynus
decentis (Bousquet and Pilon, 1977; Epstein and Kuhlman, 1990) Pterostichus adstrictus
(Goulet, 1974), P mutus (Bousquet and Pilon, 1977; Liebherr and Mahar, 1979; Bousquet,
1986), P pensylvanicus (Goulet, 1974; Bousquet and Pilon, 1977; Liebherr and Mahar, 1979;
Bousquet, 1986) and Sphaeroderus lecontei (Bousquet and Pilon, 1977; Bousquet and Pilon,
1980), probably would have appeared in our data had we been able to continue sampling
into the fall season. Flexible reproductive strategies that allow overwintering in either the
larval or adult stage (Bousquet and Pilon, 1977) or continuous reproduction as long as
TABLE4. -Incidental trap catch of mammals in pitfall traps used to characterize forest Coleoptera of the Great Lakes region in 1996
Date
Species 5/29-6/5 6/6-6/17 6/18-6/29 6/30-7/11 7/12-7/23 7/24-8/4 8/5-8/19 8/20-8/30 Total
$
Blarina brevicaudaS ay (short tailed shrew) 4 16 8 19 16 34 23 20 140
Clethrionomygsa pperiV igors (red backed vole) 0 6 4 8 7 8 10 5 48
Condylurac ristataL innaeus (star-nosed mole) 0 0 1 0 1 1 0 0 3
Napaeozapusi nsignis Miller (woodland jumping mouse) 0 0 0 0 0 7 2 1 10
Peromyscussp . (deer or white-footed mouse) 0 1 1 12 27 18 14 4 77
Sorexa rcticusK err (arctic shrew) 0 1 1 3 0 2 2 1 10
Sorexc inereusK err (masked shrew) 1 8 10 50 25 38 52 34 218
Sorexh oyiB aird (pygmy shrew) 0 0 0 2 7 11 4 0 24 g
Sorexp alustrisR ichardson (water shrew) 0 0 0 1 1 1 0 0 3
Sorexs p. 0 0 0 1 0 0 0 0 1
Synaptomycso operBi aird (southern bog lemming) O O O O O 1 0 0 1
Zapus hudsoniusZ immerman (meadow jumping mouse) 0 0 0 1 1 8 17 2 29
Total/Collection 5 26 25 97 85 129 124 66 564