Phalangids (Arachnida: Opiliones) Associated with Strip
Clearcut and Dense Spruce-fir Forests of Maine1
DANIEL T. JENNINGS, MARK W. HOUSEWEART,2
AND JAMES C. COKENDOLPHER3
U.S. Department of Agriculture, Forest Service,
Northeastern Forest Experiment Station, Orono, Maine 04469
Environ. Entomol. 13: 1306-1311 (1984)
Five genera and at least seven species of phalangids were collected by pitfall
traps in a spruce budworm-infested forest in northern Maine. More than 90% of the specimens were Leiobunum calcar (Wood). Significantly more individuals and species were
trapped in uncut residual strips and in dense spruce-Eir stands than in clearcut strips. Peaks
in seasonal activity for both individuals and species coincided with spruce budworm egg
and early larval stages. Species diversity indices were low; individuals were distributed
unevenly among the forest conditions investigated. However, coefficients of community (CC)
and percentage similarity (PS) generally were >80% for strip clearcuts (both uncut residual
and clearcut strips) and dense stands. Greater disparities (i.e.,lower CC and PS percentages)
were noted among uncut residual and clearcut strips. Neither age of strip clearcut (1 to 6
years) nor depth of litter had much influence on mean catches and mean numbers of species
of phalangids per trap per week.
ABSTRACT
PHALANGIDS
or harvestmen are predatory arachnids that feed on a variety of invertebrates, chiefly
insects (Bishop 1949, Edgar 1971 and references
cited therein). They are also scavengers and feed
on dead insects (Todd 1950). Although phalangids
attack and feed on lepidopterous larvae, pupae,
and adults, little is known of their importance as
predators of the spruce budworm, Choristoneura
fumiferana (Clemens).
Information is also sparse on the species of phalangids associated with spruce-fir forests of Maine.
Banks (1902) listed five species from Mt. Katahdin,
Piscataquis County, Maine. Procter (1946) listed
seven species from various habitats on Mount Desert Island, Hancock County, Maine.
In 1977 and 1978, we investigated the epigeal
phalangid fauna of strip clearcut and dense sprucefir forests of northern Maine. Our objectives were:
1 ) to determine the species of phalangids found in
uncut residual strips, clearcut strips, and dense
(control) spruce-fir stands, 2) to determine their
seasonal activity as related to spruce budworm development, and 3) to determine if strip clearcutting influenced the diversity and evenness of phalangid species.
!
!
Materials and Methods
Study Area. Phalangids were studied in a dense
spruce-fir forest infested with spruce budworm.
Portions of the forest had been strip clearcut by
mechanical harvesting, which created open areas
with abundant shrubs and forbs, mainly Rubus spp.
Strip clearcutting resulted in alternating clearcut
and uncut residual strips (Fig. 1). Individual study
sites were located from 48 to 61 km NW of Millinocket, Piscataquis County, Maine. Elevations
ranged from ca. 360 to 425 m. Details of forest
stand characteristics, soils, spruce budworm defoliation and population estimates, and study period
weather are described by Jennings and Houseweart (unpublished data).
T h e study area was sprayed with Sevin-4-oil@
for spruce budworm suppression in 1976, but was
not sprayed in 1977 or 1978. The forest stands
previously had been infested with spruce budworm for 4 to 5 years.
Five strip clearcuts and five nearby dense (uncut control) stands were investigated in 1977; seven strip clearcuts and three dense stands were investigated in 1978. Strip widths ranged from 23.4
to 49.7 m for uncut residual strips and from 19.1
to 29.7 rn for clearcut strips investigated in 1977.
Strip widths were not measured in 1978 but were
I This article presents the results of research only. Mention of
comparable to those studied in 1977.
a oroorietarv oroduct does not constitute an endorsement or a
Pitfall T r a ~ s .W e used laree-ca~acitv itf fall
rkommendatibn for its use by USDA.
traps for collecting and inventorying phalangids;
'Cooperative Forestry Research Unit, College of Forest Re- d etails of trap dimensions, assembly, and servicing
sources, Univ. of Maine, Orono, M E 04469.
. .by Houseweart
.
et
(1979). Four
%Dept.of Biological Sciences, Texas Tech Univ., Lubbock, T X were described
79409.
traps were deployed in each strip-clearcut area,
L,
. ,.
October 1984
JENNINGS ET AL.:
PHALANGIDS
OF SPRUCE-FIR FORESTS
1307
Table 1. Species and numbers of phalangids collected
in pitfall traps from three forest conditions, Telos Lake
area, Piscataquis County, Maine, 1977 and 1978
Forest condition
Phalangid species
Clearcut R ual
a i d - D~~~~ Total
%
strips strips Stands
1977
M . mmio (Fabricius)
0.
pictw (Wood)
L. elegans (Weed)
L. calcar (Wood)
Subtotals: Species
Individuals
34
2
102
1
102
282
3
318
3
12
1
1
1
6
105
13
4
55
1
1
551
4
608
89
3
1
935
4
1,028
8.66
0.29
0.10
90.95
67
1
8
1
175
26
13
2
1
7.29
1.08
0.54
0.08
0.04
0.29
0.08
90.59
1978
M ,morio (Fabricius)
- -
- -
STAND
I
I
Fig. 1. Schematic diagram of pitfall trap layout in
strip clearcuts (uncut residual and cut strips) and nearby
dense spruce-fir stands.
4
one each in two uncut residual strips and in two
cut strips (Fig. 1).Correspondingly, four traps were
placed in each nearby dense stand investigated.
Trap spacings in strip clearcuts were duplicated in
dense stands. Traps were installed on 26 May 1977,
and contents collected weekly for 10 weeks from
2 June to 4 August. In 1978, traps were installed
on 1 8 May and contents collected weekly for 11
weeks from 25 May to 3 August.
Trapped specimens were sorted in the laboratory; all phalangids were removed and stored in
2-dram neoprene-stoppered vials containing 70%
ethanol. Species identifications were made with the
taxonomic keys of Bishop (1949) and Davis (1934).
Species determinations were verified by comparing descriptions with those of Bishop (1949), Davis
(1934), and Shear (1975a,b). Nomenclatural and
taxonomic changes of Cokendolpher (1981, 1984)
were followed. The single specimen not identified
to species probably represents the fourth Leiobunum sp. of the region. Voucher specimens of phalangid species were deposited in the arachnid collections of the American Museum of Natural
History, New York, and the Canadian National
Collections of Insects, Arachnids, and Nematodes,
Ottawa.
Data Analyses. Data on pitfall catches were subjected to Hartley's Test for homogeneity of variance before statistical analyses. Natural log transformations, In (x l ) , were used to stabilize
variances. Analysis of variance and Duncan's multiple range test were used to evaluate differences
among catches by forest condition (uncut residual
+
0.
pictus (Wood)
C. agtlis Banks
S . caoicolens (Packard)
Leiobunum sp.
L. uentrfcosum (Wood)
L. elegans (Weed)
L. calcar (Wood)
Subtotals: Species
Individuals
589
7
613
1
7
2
861
6
986
2
2,176
8
2,402
726
5
803
strips, cut strips, and dense stands). Regression
analyses were used to evaluate the relationships
between strip-clearcut age (1to 6 years) (independent variable) and mean catches of individuals and
species (dependent variables) per trap per week.
Similar analyses were used to evaluate relationships between litter depth (cm) and mean catches
of individuals and species.
Because our pitfall collections probably d o not
represent true random samples of epigeal phalangid populations, we used Brillouin's diversity index to calculate species diversity (Pielou 1975).
Likewise, a measure of evenness was determined
by the formula J = H/H,, where H is Brillouin's
diversity and H,, is the maximum possible diversity. Two measures of similarity among forest conditions were made using coefficient of community
(CC) and percent similarity (PS) (Pielou 1975),
where CC measures similarity between species lists
and PS measures similarity between species quantities.
Results
Numbers of Individuals and Species. Three
genera and four species of phalangids were collected in 1977; five genera and at least seven species
were collected in 1978 (Table 1). All four species
collected in 1977 were collected again in 1978; in
addition, Caddo agilts Banks, Sabacon cavicolens
(Packard), and Leiobunum ventricosum (Wood)
were trapped in 1978, but not in 1977. For both
years, more than 90% of the specimens caught were
Leiobunum calcar (Wood). Mitopus morio (Fa-
1308
ENVIRONMENTAL
ENTOMOLOGY
Table 2. Mean numbers of individuals and phalangid
species per trap per week by forest condition
Forest condition
Clearcut strips
Residual strips
Dense stands
f
No. of individuals
f
1977
1978
1977
1978
1.02a
3.18b
3.04b
4.01a
6.40b
6.08b
0.35a
0.77b
0.70b
0.75a
1.16b
1.08b
Vol. 13. no. 5
7
i\
A-A
No.of species
Dense spruce-fir stands
*-a
U ~ Uresidual
I
strips
m-m
Cut strips
Column means followed by the same letter are not significantly
different (P 5 0.05; Duncan's multiple range test).
W
-
bricius) was next in abundance but represented
less than 10%of the total specimens caught in either
year; the remaining six species combined accounted for less than 3%.
Four species, Mitopus morio, Odiellus pictus
(Wood), Caddo agilis, and Lehbunum calcar, were
found in all three forest conditions (dense stands,
uncut residual strips, and cut strips), but not consistently among years (Table 1). Leiobunum elegans (Weed) was found only in uncut residual strips
and in dense stands; L. uentricosum was found
only in strip clearcuts, including both uncut residual and cut strips. Sabacon cavicolens was found
in a cut strip and in a dense stand; Leiobunum sp.
was found only in a cut strip.
In 1977, more specimens were collected in dense
spruce-fir stands (608) than in either cut strips (102)
or in uncut residual strips (318). In 1978, the order
of abundance was residual strips (986), dense stands
(803), and cut strips (613).
Mean Individuals and Species. For both study
years, significantly more (P 5 0.05) individuals and
more (P r 0.05) species were caught in uncut residual strips and in dense stands than in cut strips
(Table 2). No significant differences in mean individuals or species were detected between dense
stands and residual strips in either year, reflecting
similarities of these forest conditions. During 1977,
about 3-fold as many individuals were collected
per trap per week in dense stands and in residual
strips as in cut strips; in 1978, only about 1.5-fold
as many individuals were caught in either dense
stands or residual strips as in cut strips.
The ratio of species trapped per week in residual and dense stands compared with cut strips was
about 2.0 in 1977 and 1.5 in 1978.
Comparing catches among years showed that
from 2.0- to 3.9-fold more individuals and 1.5- to
2.1-fold more species were caught per trap per
week in 1978 as in 1977. We were unable to determine the factors responsible for these yearly differences.
Comparing mean catches in strip clearcuts (residual cut strips) and in dense stands showed that
in 1977 significantly more ( P I0.05) phalangids
were caught in dense stands (mean = 3.04) than in
strip clearcuts (mean = 2.10). However, in 1978,
differences in mean catches were nonsignificant
among strip clearcuts (mean = 5.21) and dense
stands (mean = 6.08). Likewise, significantly more
+
WEEK
Fig. 2. Mean catch of phalangids per trap per week;
week 1 = 2 June 1977.
( P i 0.05) species were caught in dense stands
(mean = 0.70) than in strip clearcuts (mean = 0.56)
in 1977, but not in 1978 (dense stands: mean =
1.08; strip clearcuts: mean = 0.96).
Seasonal Activity. In 1977, mean catches per
trap peaked on week 8 for all three forest conditions (dense stands, uncut residual strips, and cut
strips) (Fig. 2); a minor peak also was evident during week 4 of trapping for residual strips. During
1978, mean catches per trap generally were greater than in 1977; peaks were evident during week
8 (cut strips) and week 9 (uncut residual strips and
dense stands) (Fig. 3).
Mean numbers of species per trap per week were
2.0 for all three forest conditions in 1977, and were
slightly greater and more erratic in 1978 (Fig. 4
and 5). For both years, more species usually were
caught in dense stands and in uncut residual strips
than in cut strips. Although weekly species means
fluctuated widely in early 1978, both years showed
rising trends as the season progressed.
Species Diversity and Evenness. Because one or
two species of phalangids were more abundant than
others, species diversity indices were low (Table
3). Strip clearcuts (residual cut strip) and dense
stands had about equal diversities of phalangid
species both study years. Individuals were distributed unevenly among species both for the different forest conditions and for years of investigation.
Coefficient of Community and Percent Similarity. Strip clearcuts had more phalangid species
in common with dense stands in 1977 (CC = 86)
than in 1978 (CC = 80). However, comparison of
catches within strip clearcuts (i.e., uncut residual
vs. cut strips) showed that fewer species shared
+
4
October 1984
JENNINGS
ET
AL.:
PHALANGIDS
OF SPRUCE-FIR
FORESTS
I
1
O
0
C
I
I
2
I
I
I
I
6
WEEK
4
I
I
8
I
I
10
I
I
1309
Dense spruce-fir stands
nr-.
Uncut residual slrips
m-• c u t strips
Fig. 4. Mean species of phalangids per trap per week;
week 1 = 2 June 1977.
Fig. 3. Mean catch of phalangids per trap per week;
week 1 = 25 May 1978.
these habitats in 1977 (CC = 50) than in 1978
(CC = 77).
Percentage of similarity in numbers of individuals of each species generally was high among strip
clearcuts (residual cut strips) and dense stands
for both years (PS = 82 in 1977 and 96 in 1978).
But uncut residual and cut strip habitats were less
similar in numbers of each species caught in 1977
(PS = 49) than in 1978 (PS = 76).
Age of Strip Clearcut. Regression analyses indicated that age of strip clearcut (1to 6 years) had
little influence on mean catches (RP = 0.00) and
mean species (R2= 0.02) of phalangids per trap
per week.
Litter Depth. Mean litter depth was significantly greater (P I0.01) in dense stands (mean = 11.7
cm) than in either uncut residual strips (mean =
8.5 cm) or in cut strips (mean = 8.0). Uncut residual and cut strip means did not differ significantly.
Regression analyses indicated that litter depth had
little influence on either mean catches of phalangids (Rg= 0.12, dense stands; R2 = 0.04, uncut residual strips; R2 = 0.02, cut strips), or on mean
number of phalangid species (R2= 0.11, dense
stands; RZ= 0.01, uncut residual strips; R2= 0.07,
cut strips) per trap per week.
+
1
Discussion
Most of the phalangid species we collected in
northern Maine have been found in other northeastern spruce-fir forests infested with spruce budworm. Carter and Brown (1973) reported six
species, Caddo agilis Banks, Sabacon crassipalpe
(L. Koch), Odiellus pictus (Wood), Leiobunurn
calcar (Wood), L. bicolor (Wood), and L. uentricosum (Wood) from pitfall traps in a mature red
spruce, Picea rubens Sargent, stand in New Brunswick. All except L. &color also were collected in
budworm-infested fir-spruce stands in New Brunswick by Varty and Carter (1974).
Apparently, the Sabacon species reported in
Carter and Brown (1973) and Varty and Carter
(1974) was misidentified because S. crassipalpe (L.
Koch) is known only from eastern Siberia (Shear
1975b). There is little doubt that the specimens in
question are S . caufcolens, the same as we report.
Due to a nomenclatural change (Cokendolpher
1984), the species reported by Carter and Brown
(1973) as Leiobunurn bicolor should be Leiobunum elegans. Mitopus morio has been reported
(Banks 1902, as Nitopus [sic] montanus) from birch
woods at Mt. Katahdin, Maine; apparently, this
species had not been recorded from spruce-fir forests in North America before our study.
Our results indicate that the phalangids generally preferred the more closed, shaded habitats of
dense spruce-fir stands and uncut residual strips to
the open, cleared habitats of cut strips. Significantly more (P 5 0.05) individuals and species
were caught in the residual strips and in the dense
stands than in the clearcut strips. Some of these
apparent habitat preferences may be related to
species specific requirements. For example, Leiobunum calcar, our most abundant species, is a hardy
species able to tolerate extremes of physical conditions (Edgar 1971). We found L. calcar mainly
in uncut residual strips and in dense stands, but
also in open clearcut strips. Caddo agilis and
Odiellus pictus, which prefer habitats of moderate
to dense canopies (Edgar 1971), were seldom collected in cut strips; most were caught in uncut
residual strips and dense stands.
The abundance of Leiobunum calcar and scarcity of other species, such as Sabacon cavicolens
and L. elegans, no doubt contributed to the low
1310
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1
Vol. 13, no. 5
ENVIRONMENTAL
ENTOMOLOGY
A-A
Dense spruce-flr stands
*-•
Uncut resldual straps
Table 3. Phalangid species diversity and evenness by
forest condition, Brillouin's formula
I
Diversity
Forest condition
Residual + clearcut
strips
Dense stands
Evenness
1977
1978
1977
1978
0.13
0.14
0.14
0.15
0.28
0.23
0.20
0.22
In 1977, five replicates from each forest condition, four traps
per replicate; in 1978, three replicates from each forest condition,
four traps per replicate.
0
0
2
4
,
6
I
8
I0
WEEK
F
i
g
.5. Mean species of phalangids per trap per week;
week 1 = 25 May 1978.
species diversity indices for both strip clearcuts
(residual cut strips) and dense stands. Diversity
increases as species are added and as species become evenly distributed in abundance (Price 1975).
Tables 1 and 3 indicate that phalangid individuals
were distributed unevenly among species for both
forest conditions and years of investigation.
As expected, both measures of similarity among
forest conditions (i.e., coefficient of community and
percent similarity) indicated that species and individuals were shared in common among strip
clearcuts and dense stands. Likewise, the most dissimilar neighboring habitats (i.e., uncut residual
and cut strips) had fewer species and individuals
in common.
Our results were somewhat conflicting regarding possible effects of strip clearcutting on phalangid species and populations. In 1977, dense
stands supported significantly greater populations
of phalangids than strip clearcuts, but in 1978,
populations were about equal among dense stands
and strip clearcuts. Species diversity also was about
the same among the two forest conditions for both
years. We conclude that strip clearcutting may alter species diversity and abundance of phalangids,
particularly in the open, cleared strips, but that
the uncut residual stands offer islands of "refugia"
where phalangid populations are abundant and diverse.
Although we detected little influence of stripcut age (1 to 6 years) and litter depth on mean
catches and species of phalangids, we suspect that
age (indirectly) becomes increasingly important
during later successional stages when regeneration
causes canopy closure. Edgar (1971) found that
canopy cover greatly influenced phalangid abundance in Michigan forests.
+
Most important, our results indicate that for both
years of investigation, phalangids were most abundant (Fig. 2 and 3) during the egg and first-instar
larval periods of the spruce budworm. Spruce budworm egg deposition generally spans 27 days in
late June and July (Houseweart et al. 1982). After
egg hatch (ca. 10 days), the young larvae disperse
and seek overwintering sites; however, many are
lost during dispersal. Strip clearcutting contributes
to dispersal losses of early instar larvae (Jennings
et al. 1983), and during dispersal the larvae are
exposed to numerous predators, including ants,
spiders, and phalangids.
Although phalangids were not observed feeding
on either budworm eggs or young larvae, we suspect these stages are susceptible to predation. Varty and Titus (1974, p. 17) included phalangids
among the arthropods that "exercise a light restraint on budworm abundance in the egg and
small-larval stages, but have virtually no importance in the survival of large-larval budworms, pupae, or adults."
Additional studies are needed to ascertain the
predatory roles of phalangids in spruce-fir forests
and their effects on spruce budworm populations.
Such studies will require special techniques to elucidate predator-prey relationships. Loughton et al.
(1963) included phalangids among the predators
that could be assessed serologically for predation
on spruce budworm.
Acknowledgment
We thank our former technicians for field and laboratory assistance: Deirdre M. Haneman, Janice E. Littlefield, Susan L. May, Susan M. Sheffer, Denise E. Stephens, Michael Wissenbach, and Wesley A. Wright.
Special thanks to David M. Kendall for preparing data
summaries, to Richard A. Hosmer for assisting in computer programming, and to James Lockyer for preparing illustrations. We also thank reviewers Charles D.
Dondale, Arlan L. Edgar, and George W. Uetz. This
paper is a contribution to the CanadaIUnited States
(CANUSA) Spruce Budworms Program.
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Maine. Entomol. News 13: 308-309.
Bishop, S. C. 1949. The Phalangida (Opiliones) of
New York. Proc. Rochester Acad. Sci. 9: 159-235.
Carter, N. E., a n d N. R. Brown. 1973. Seasonal abunBanks, N.
October 1984
8
I
JENNINGS ET AL.:
PHALANGIDS
OF SPRUCE-FIRFORESTS
dance of certain soil arthropods in a fenitrothiontreated red spruce stand. Can. Entomol. 105: 10651073.
Cokendolpher, J. C. 1981. Status of Leiobunum serratipalpe Roewer (Opiliones, Leiobunidae). J. Arachnol. 9: 112-113.
1984. Homonyms of American and European Leiobunum (Opiliones, Palpatores, Leiobuninae). Ibid. 12:
118-119.
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15: 662-705.
Edgar, A. L. 1971. Studies on the biology and ecology
of Michigan Phalangida (Opiliones). Univ. Mich. Mus.
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Houseweart, M. W., D. T. Jennings, and J. C. Rea.
1979. Large capacity pitfall trap. Entomol. News
90: 51-54.
Houseweart, M. W., S. C. Southard, and D. T. Jennings. 1982. Availability and acceptability of
spruce budworm eggs to parasitism by the egg parasitoid, Trichogramma minutum (Hymenoptera:
Trichogrammatidae). Can. Entomol. 114: 657-666.
Jennings, D. T., M. W. Houseweart, and J. B. Dirnond.
1983. Dispersal losses of early-instar spruce budworm (Lepidoptera: Tortricidae) larvae in strip
clearcut and dense spruce-fir forests of Maine. Environ. Entomol. 12: 1787-1792.
Loughton, B. C., C. Derry, and A. S. West. 1963.
Spiders and the spruce budworm, pp. 249-268. In
R. F. Morris [ed.], The dynamics of epidemic spruce
1311
budworm populations. Mem. Entomol. Soc. Can. No.
31.
Pielou, E. C. 1975. Ecological diversity. John Wiley
& Sons, Inc., New York.
Price, P. W. 1975. Insect ecology. John Wiley & Sons,
Inc., New York.
Procter, W. 1946. Biological survey of the Mount
Desert Region Incorporated. Part VII. Wistar Institute of Anatomical Biology, Philadelphia.
Shear, W. A. 1975a. The opilionid family Caddidae
in North America, with notes on species from other
regions (Opiliones, Palpatores, Caddoidea). J. Arachnol. 2: 65-88.
197513. The opilionid genera Sabacon and Tomicomerus in America (Opiliones, Trogulidae, Ischyropsalidae). Ibid. 3: 5-29.
Todd, V. 1950. Prey of harvestmen (Arachnida, Opiliones). Entomol. Mon. Mag. 86: 252-254.
Varty, I. W., and N. E. Carter. 1974. A baseline inventory of litter-dwelling arthropods and airborne
insects including pollinators in two fir-spruce stands
with dissimilar histories of insecticide treatment. Can.
For. Serv. Marit. For. Res. Cent. Inf. Rep. M-X-48.
Varty, I. W., and F. A. Titus. 1974. Effects of phosphamidon sprays on non-target insects in fir-spruce
forest, spruce budworm adulticide trials 1973. Ibid.
M-X-47.
Received for publication 6 March 1984; accepted 22
May 1984.