B-l 707

1 uuu
Z TA245.7
October i992

B873
NO. 1707

T)

)

SPIDERS
 Associated with

'\

  -\ Lemon llorsemint

\

\
l \

  (Monarda citriodora Cervantes)

n East Central Texas

)

The Texas Agricultural Experiment Station - Edward A. Hiler, Director ~ The Texas A&M University System ~ College Station, Texas

‘a

  <1; ..

[Blank Page in Original Bulletin] '

Age

Spiders Associated with
Lemon Horsemint (Monarda citriodora Cervantes)
in East Central Texas

by M. Nyffeler, D. A. Dean, and W. L. Sterlingl

Abstract

Spider predators were studied on flowering lemon horsemint, Monarda citriodora Cervantes, Lamiaceae, at two Texas
locations to assess their potential as agroecosystem colonizers and natural control agents of insect pests. Oxyopes salticus
Hentz, Peucetia viridans (Hentz), Misumenops celer (Hentz), and Metaphidippus galathea (Walckenaer) were predominant and
are known (1) to disperse via air currents (ballooning), (2) to colonize cotton fields, and (3) to forage on cotton insect pests.
About 90% of the spider individuals found on horsemint plants represent species known to attack and kill cotton
fleahoppers, Pseudatomoscelis seriatus (Reuter), a key pest of cotton.

Keywords: horsemint, wild plants, spiders, predators, cotton fleahopper, Texas

Introduction

Wild plants growing in minimally disturbed noncrop
land may be ecologically important as a reservoir of ben-

_f\ eficial natural enemies (i.e., predaceous insects and spi-

ders) that continuously re-colonize annual field crops
(Altieri and Whitcomb 1979, 1980). Migration of spiders
from reservoir habitats into adjacent agroecosystems was
shown by Bishop and Riechert (1990) with a mark-recap-
ture method. Wild plants also serve as alternate hosts for
many insect pests (Stadelbacher and Lockley 1983,
Nyffeler and Benz 1987, Breene et al. 1988). Faunistic
surveys of the natural enemy complex associated with
some wild plants are therefore an important step in under-
standing the mechanisms and effects of predator dispersal
in the agricultural landscape.

This publication reports on the spider complex associ-
ated with lemon horsemint, Monarda citriodora Cervantes,
Lamiaceae, in Central Texas. Growing along roadsides, in
pastures, and on the borders of crop fields, lemon horse-
mint is an important wild host plant of the cotton fleahop-
per, Pseudatomoscelis seriatus (Reuter). The potential of the
beneficial spider complex as cotton field colonizers and as
predators of cotton fleahoppers is discussed in light of
their dispersal capacities and prey-size selection.

Materials and Methods

We conducted this study in 1988 at two locations in
Snook (near College Station), Burleson County, Central

‘Respectively, visiting scientist, technician II, and professor,
Department of Entomology, Texas A&M University, College
Station, Texas 77843

Texas. This area is dominated by grassland, cotton, sor-
ghum, and corn fields. Site 1 was a horsemint-dominated
pasture, and at site 2, horsemint patches grew along a
highway. Sampling at site 1 was conducted on 8 Iune 1988
(1450 to 1850) and 9 June 1988 (1510 to 1810); at site 2 on 13
June 1988 (1400 to 1720) and 14 Iune 1988 (1620 to 1920).
The horsemint plants were in bloom on all four dates, and
sampling was conducted under warm, sunny weather.

We sampled spiders with a standard sweep-net (38-cm
diameter) at an average of 400 sweeps per hour. Spiders
were removed from the sweep-net, killed, preserved in
70% ethyl alcohol, and identified under a dissecting micro-
scope (Table 1). Immature spiders were identified as far as
possible. Spider Genera of North America (Roth 1985) con-
tains references to the taxonomic literature used in this
study. We deposited voucher specimens in the Depart-
ment of Entomology collection at Texas A&M University.

An assessment of the age/ size structure of the spiders
found on horsemint provided information on their colo-
nizing capability because ballooning is a function of spider
body length (Dean and Sterling 1985). Spider size may also
be critical in determining which species can be classified as
a ”key predator” (Sterling et al. 1989). The size class
distribution was assessed by assigning each collected
spider (Table 1) to one of five size classes according to
length (1 to 2, 2 to 3, 3 to 4, 4 to 5, > 5 mm; Table 2). The
length was measured from the anterior margin of the
carapace to the apex of the abdomen, excluding the spin-
nerets.

Ecological characterization of these spiders is based on
data from previous studies in Texas (Dean et al. 1982, 1987,
1988; Dean and Sterling 1987, 1990; Breene et al. 1988,
1989b; Nyffeler et al. 1992a, b).

Table 1. Spiders found on horsemint (Monarda citriodora) at two locations in Central Texas, 1988, and characterized as follows:

ballooning’ - colonizers of cotton fieldsb - predators of the cotton fleahopper.‘

"§

Family and Species Site 1 Site 2 Total Characterization‘
Dictynidae q
Dictyna segregate: Gertsch and Mulaik 5 1 6 (0.3%) ab‘
Theridiidae
Achaearanea sp. 1 1 2 (0.1%)
Theridion sp. 3 3 6 (0.3%)
Linyphiidae
Ceraticelus sp. A 1 1 2 (0.1%)
Ceraticelus sp. B 10 5 15 (0.7%)
Eperigone eschatologica Crosby 3 0 3 (0.1%) ab
Erigone autumnalis Emerton 1 O 1 (<0.1%) ab
Grammonota texana (Banks) 5 44 49 (2.3%) ab‘
Other 18 10 28 (1.3%)
Tetragnathidae
Tetragrwtha laboriosa Hentz 6 2 8 (0.4%) ab”
Araneidae
Acanthepeira stellata (Walckenaer) 0 2 2 (0.1%) ab”
Araneus sp. 1 1 2 (0.1%)
Argiope sp. 0 1 1 (<0.1%)
Cyclosa turbinata (Walckenaer) 1 1 2 (0.1%) ab‘
Eustala sp. 4 2 6 (0.3%) ‘X
Gea heptagon (Hentz) 2 0 2 (0.1%) “b” I
Neoscona ambesca (Walckenaer) 4 9 13 (0.6%) ab”
Other 0 1 1 (<0.1%)
Lycosidae
Pardosa sp. 12 1 13 (0.6%)
Oxyopidae
Oxyopes salticus Hentz 451 12s 579 (2770/0) W
Peucetia viridans (Hentz) 51 79 130 (6.2%) W
Gnaphosidae
Micaria sp. 1 0 1 (<0.1%)
Clubionidae
Clubiona abboti L. Koch 1 2 3 (0.1%) a/b
Anyphaenidae
Aysha sp. s 2s 36 (1.7%)
Thornisidae
Misumenoidesformosipes (Walckenaer) 2 1 3 (0.1%) b
Misumenops celer (Hentz) adults 112 53 165 (7.9%) ab” q
Misumenops dybius (Keyserling) adults 6 9 15 (0.7%) b
Misumenops slijp. immatures 387 301 688 (32.9%)
Xysticus auctificus Keyserling 7 16 23 (1.1%) b
Philodromidae ,
Ebo sp. 11 0 11 (0.5%) q
Philodromus pratariae (Scheffer) 1 0 1 (<0.1%) ab‘
Thanatusformicinus (Clerck) 0 1 1 (<0.1%) b
Tibellus duttoni (Hentz) 12 11 23 (1.1%) b‘

Table 1. cont.

£Family and Species Site 1 Site 2 Total Characterization‘
Salticidae
g Eris aurantia (Lucas) 0 1 1 (<0.1%)

Habronattus coecatus (Hentz) 11 1 12 (0.6%) ab‘
Hentzia palmarum (Hentz) 0 1 1 (<0.1%) ab‘
Metaphidippus galathea (Walckenaer) 77 116 19s (920/0) ab‘
Phidippus audax (Hentz) 11 14 25 (1.2%) W
Phidippus clarus Keyserling 1 0 1 (<0.1%) b
Phidippus pius Scheffer 1 0 1 (<0.1%)

Sarinda hentzi (Banks) s 0 s (0.40%) “I”
Zygoballus nervosus (G. and E. Peckham) 5 1 6 (0.3%) a)’
Zygoballus rufipes G. and E. Peckham 2 0 2 (0.1%) ab‘

TOTAL SPIDERS 1,243 848 2,091 (100%)

* Based on the following literature:
aDean and Sterling (1990).

b Dean et al. (1982, 198s), Dean and Sterling (19s7), Breene et al. (1989b).
C Dean et al. (1987), Breene et al. (1988, 1989b), Nyffeler et al. (1992b).

Results and Discussion

Spider Assemblages on Horsemint Plants

Table 1 presents a species list (representing 13 families)
of spiders associated with flowering horsemint plants.

f?\ The taxonomic composition of the spider assemblages at

two sites was similar. Three families of nonweb-building
spiders (foraging without a web) predominated: lynx
spiders (Oxyopidae), crab spiders (Thomisidae), and j ump-
ing spiders (Salticidae). The lynx spiders Oxyopes salticus
Hentz and Peucetia viridans (Hentz), the crab spider
Misumenops celer (Hentz), and the jumping spider
Metaphidippus galathea (Walckenaer) constituted > 75% of
the total number of spider individuals collected at each site
(Table 1). These four species typically inhabit wild plants
in Texas (Dean and Eger 1986; Dean et al. 1987, 1988;
Breene et al. 1988), and they are also prominent
agroecosystem spider species (Johnson et al. 1986,Dean
and Sterling 1987, Nyffeler et al. 1987a). All identifiable
spider species listed in Table 1 have been reported in U.S.
field crops (Young and Edwards 1990).

We observed a consistent trend of a sex ratio biased
toward females (Table 2) and a statistically significant
deviation (p < 0.01, chi-square test for 2 x 2 contingency
table; pooled data for each site) from a theoretical sex ratio
of 1 femalezl male. For a hypothetical explanation of the
biased sex ratio, see Huhta (1965). The sex ratio is of
ecological importance because the heavier females have
higher energy requirements compared with the males
(sexual dimorphism; Muniappan and Chada 1970, Homer

fx 1972, Nyffeler et al. 1987b). Immature stages (> 80% of total

spider individuals) having high dispersal capacity (see
section on “Horsemint Plants as a Reservoir for Spider
Colonization of Cotton Fields”) outnumbered the adults
(Table 2).

Horsemint Plants as a Reservoir for
Spider Colonization of Cotton Fields

In the cotton agroecosystem, growers periodically de-
stroy the vegetation at the end of the growing season. The
system therefore becomes an ”ecological desert” (except
for soil arthropods) during winter and must be re-colo-
nized by predators each spring (Dean and Sterling 1992).
Ballooning appears to be the primary mode by which
spiders colonize cultivated fields (Bishop and Riechert
1990). In Texas, Dean and Sterling (1992) measured spider
ballooning by means of a Johnson-Taylor suction trap and
compared these counts with counts of spiders in a local
insecticide-free (8-ha) cotton field. Levels of ballooning
activity were high early in the season and declined with the
progressing season. Spider numbers on cotton plants
increased inversely, suggesting that spiders ballooning
early in the season into the cotton field tend to remain there
(Dean and Sterling 1992).

Spiders associated with horsemint plants had an early-
season age / size structure (> 70% of all collected individu-
als were S 4 mm in body length, including many immature
spiders, Table 2) favorable to dispersal by ballooning (see
Dean and Sterling 1985, 1990; Bishop 1990). More than 90%
of the spider individuals and identifiable taxa found on the
horsemint plants belong to species known to be cotton
field colonizers (Table 1).

Spiders as Predators of Insect Pests

The species of spiders found on horsemint (Table 1) are
known to be polyphagous insectivores (Muniappan and
Chada 1970, Homer 1972, Dean et al. 1987, Nyffeler et al.
1986, 1987a, b, 1989, 1990, 1992a).

l‘ iiuluiiisivl
A IL

‘+636 251L550

Table1includessixspecies,(O.salticus,M.cel;r,l;l1idippus The assemblage of spiders sampled from horsemint
audax [Hentz], Misumenoides formosipes [Walckenaer], plants (Table 2) can be expected to be effective as predators ~
Acanthepeira stellata [Walckenaer], and Tetragiwtha laboriosa on pests having small body size. The cotton fleahopper, l

[Hentz]), that may qualify as "key predators" of some Pseudatomoscelis seriatus (Hemiptera: Miridae), a major
cotton insect pests (Sterling et al. 1989). According to cotton pest in Texas that uses horsemint as an early-season
Sterling et al. (1989), the age structure of predator and prey host, varies between 1.1 and 2.9 mm in length (third instar 
is critical in determining which species of spiders can be to adult, Table 3) and ideally fits the prey-size range of the
classified as a key predator; most predators of the small spiders on horsemint (see Nyffeler et al. 1992b). Spiders
stages of insect pests are also small (i.e., immature spiders). ranging from 1.2 to 7.4 mm in length are known to attack
Table 2. Size class distribution (%) of the spiders associated with Monarda citriodora at two locations in Central Texas, June 1988.
Data are on the four dominant species and on all spiders combined (n = number of collected spiders, imm = immatures, ad = adults,
m = males, f = females).

Size class Oxyopes Peucetia Metaphidippus Misumenops

(mm) salticus“ viridansb galathea‘ sppd All spiders“

Site 1
(n = 451) (n = 51) (n = 77) (n = 505) (n = 1,243)

1-2 75.2 0.0 18.2 29.5 45.9

2-3 20.4 0.0 20.8 36.8 26.5

3-4 0.4 2.0 37.7 15.2 10.5

4-5 2.2 9.8 22.1 10.1 8.4

>5 1.8 88.2 1.3 8.3 8.7
Total 100 100 100 100 100

Site 2 q
(n = 128) (n = 79) (n = 116) (n = 363) (n = 848)

1-2 42.2 0.0 6.9 28.6 27.7

2-3 32.0 0.0 18.1 53.7 35.1

3-4 14.1 0.0 30.2 3.3 9.8

4-5 3.1 3.8 28.4 5.0 8.6

>5 8.6 96.2 16.4 9.4 18.8
Total 100 100 100 100 100

a 435 imm, 3 ad m, 13 adf(site 1); 113 imm, 0 ad m, 15 adf(site 2).

l’ 51 imm, 0 ad m, 0 ad f(site 1),- 79 imm, 0 ad m, 0 ad f (site 2).

C 49 imm, 14 ad m, 14 ad f (site 1); 53 imm, 27 ad m, 36 ad f (site 2).

d Mostly Misumenops celer; 387 imm, 56 ad m, 62 ad f (site 1); 301 imm, 21 ad m, 41 ad f (site 2).

e 1,050 imm, 86 ad m, 107 ad f (site 1); 687 imm, 53 ad m, 108 ad f (site 2).

Table 3. Body length (mm) of spiders (and prey) known to have successfully attacked and killed cotton fleahoppers. Data are from
108-hours visual observation in a cotton field near College Station, Central Texas (summer 1988, Nyffeler et al. 1992b, unpublished
data) (imm = immatures, ad = adults). See Nyffeler et al. (1987a, b) for methods information.

Predator species Life stage (instar) of Body length of predator Body length of prey

(and stage) fleahopper prey x i SE (range) x i SE (range)

O. salticus (imm, ad) imm (3rd/5th), ad 4.0 i 0.3 (2.6-5.7) 2.3 i 0.1 (1.1-2.9) Q
P. viridans  ad 6.9 i 0.3 (6.4—7.4) 2.5 i 0.2 (2.2-2.9)

P. audax (imm) -I ad 3.7 a

M. galathea (imm) imm (3rd) 3.5 1.6

Misumenops spp. (imm) ad 3.0 2.6

C. turbinata (imm, ad) ad 2.4 i 0.2 (1.9-2.8) 2.2 i 0.1 (1.8-2.6)

N. arabesca (imm) ad 2s (2s29) 2.2 0.9-2.4) t"
D. segregata (imm, ad) ad 1.8 i 0.2 (1.2-2.2) 2.2 i 0.2 (1.7-2.4)

All species combined — 3.5 i 0.3 (1.2-7.4) 2.3 i 0.1 (1.1-2.9)

a Not identified.

and kill cotton fleahoppers (Table 3, 108-hours visual
observation in a cotton field), which implies that spiders of
any length sampled from horsemint (Table 2) should be
able to overpower this cotton pest. The smallest spiders (1-
to 2-mm size class) may forage preferentially on small

A nymphs of the fleahopper.

Conclusions

Approximately 90% of the spider individuals found on
horsemint plants (Table 1) belong to species known as
predators of the cotton fleahopper (Dean et al. 1987; Breene
et al. 1988, 1989a, b, 1990; Nyffeler et al. 1992b). This
indicates that these spiders kill cotton fleahoppers on wild
plants. The TEXCIM40 model also demonstrates that
spiders are of economic value as predators of the cotton
fleahopper in Texas cotton fields (Sterling et al. 1992).

Acknowledgments

We thank R. G. Breene, E. G. Riley, and R. A. Wharton
for their comments on this paper. This project was funded
in part by project H-6903-2100 of the Texas Agricultural
Experiment Station.

Literature Cited

Altieri, M. A., and W. H. Whitcomb. 1979. Predaceous
f“ arthropodsassociatedwithMexicanteainnorthFlorida.
Florida Entomol. 62: 175-182.

Altieri, M. A., and W. H. Whitcomb. 1980. Predaceous and
herbivorous arthropods associated withcamphorweed
(Heterotheca subaxillaris Lamb.) in north Florida. I. Geor-
gia Entomol. Soc. 15: 290-299.

Bishop, L. 1990. Meteorological aspects of spider balloon-
ing. Environ. Entomol. 19: 1381-1387.

Bishop, L., and S. E. Riechert. 1990. Spider colonization of
agroecosystems: mode and source. Environ. Entomol.
19: 1738-1745.

Breene, R. G., W. L. Sterling, and D. A. Dean. 1988. Spider
and ant predators of the cotton fleahopper on woolly
croton. Southwest. Entomol. 13: 177-183.

Breene, R. G., A. W. Hartstack, W. L. Sterling, and M.
Nyffeler. 1989a. Natural control of the cotton fleahop-
per, Pseudatomoscelis seriatus (Reuter) (Herniptera,
Miridae), in Texas. I. Appl. Entomol. 108: 298-305.

Breene, R. G., W. L. Sterling, and D. A. Dean. 1989b.
Predators of the cotton fleahopper on cotton. South-

" west. Entomol. 14: 159-166.

Breene, R. G., W. L. Sterling, and M. Nyffeler. 1990. Efficacy
of spider and ant predators on the cotton fleahopper
[Hemipteraz Miridae]. Entomophaga 35: 393-401.

Dean, D. A., and I. E. Eger, Ir. 1986. Spiders associated with
Lupinus texensis (Leguminosae) and Castilleja indivisa

' ‘ (Scrophulariaceae) in south central Texas. Southwest.
Entomol. 11: 139-147.

Dean, D. A., and W. L. Sterling. 1985. Size and phenology
of ballooning spiders at two locations in eastern Texas.
I. Arachnol. 13: 111-120.

Dean, D. A., and W. L. Sterling. 1987. Distribution and
abundance patterns of spiders inhabiting cotton in
Texas. Texas Agric. Exp. Stn. Bull. 1566.

Dean, D. A., and W. L. Sterling. 1990. Seasonal patterns of
spiders captured in suction traps in eastern Texas.
Southwest. Entomol. 15: 399-412.

Dean, D. A., and W. L. Sterling. 1992. Comparison of
sampling methods to predict phenology of predaceous
arthropods in a cotton agroecosystem. Texas Agric.
Exp. sm. Misc. Publ. 1731. ‘

Dean, D. A., M. Nyffeler, and W. L. Sterling. 1988. Natural
enemies of spiders: mud dauber wasps in east Texas.
Southwest. Entomol. 13:283-290.

Dean, D. A., W. L. Sterling, and N. V. Homer. 1982. Spiders
in eastern Texas cotton fields. I. Arachnol. 10: 251-260.

Dean, D. A., W. L. Sterling, M. Nyffeler, and R. G. Breene.
1987. Foraging by selected spider predators on the
cotton fleahopper and other prey. Southwest. Entomol.
12: 263-270. a

Horner, N. V. 1972. Metaphidippus galathea as a possible
biological control agent. I. Kans. Entomol. Soc. 45: 324-
327.

Huhta, V. 1965. Ecology of spiders in the soil and litter of
Finnish forests. Annls. Zool. Fenn. 2: 260-308.

Iohnson, S. I., H. N. Pitre, I. E. Powell, and W. L. Sterling.
1986. Control of Heliothis spp. by conservation and
importation of natural enemies. In Theory and tactics of
Heliothis population management: I. Cultural and bio-
logical control. S.I. Iohnson, E.G. King, and I.R. Bradley,
Ir. (eds.), South. Coop. Ser. Bull. 316, pp. 132-154.

Muniappan, R., and H. L. Chada. 1970. Biology of the crab
spider, Misumenops celer. Ann. Entomol. Soc. Am. 63:
1718-1722.

Nyffeler, M., and G. Benz. 1987. Spiders in natural pest
control: a review. I. Appl. Entomol. 103: 321-339.

Nyffeler, M., R. G. Breene, D. A. Dean, and W. L. Sterling.
1990. Spiders as predators of arthropod eggs. I. Appl.
Entomol. 109: 490-501. l

Nyffeler, M., D. A. Dean, and W. L. Sterling. 1986. Feeding
habits of the spiders Cyclosa turbinata (Walckenaer) and
Lycosa rabida Walckenaer. Southwest. Entomol. 11: 195-
201.

Nyffeler, M., D. A. Dean, and W. L. Sterling. 1987a. Preda-
tion by green lynx spider, Peucetia viridans (Araneae:
Oxyopidae), inhabiting cotton and woolly croton plants
in east Texas. Environ. Entomol. 16: 355-359.

Nyffeler, M., D. A. Dean, and W. L. Sterling. 1987b. Evalu-
ation of the importance of the striped lynx spider,
Oxyopes salticus (Araneae: Oxyopidae), as a predator in
Texas cotton. Environ. Entomol. 16: 1114-1123.

Nyffeler, M., D. A. Dean, and W. L. Sterling. 1989. Prey
selection and predatory importance of orb-weaving
spiders (Araneae: Araneidae, Uloboridae) in Texas cot-
ton. Environ. Entomol. 18: 373-380.

Nyffeler, M., D. A. Dean, and W. L. Sterling. 1992a. Diets,
feeding specialization, and predatory role of two lynx
spiders, Oxyopes salticus and Peucetia viridans (Araneae:
Oxyopidae), in a Texas cotton agroecosystem. Environ.
Entomol. (in press).

Nyffeler, M., W. L. Sterling, and D. A. Dean. 1992b. Impact
of the striped lynx spider (Araneae: Oxyopidae) and
other natural enemies on the cotton fleahopper
(Hemiptera: Miridae) inTexas cotton. Environ. Entomol.
(in press).

Roth, V. D. 1985. Spider Genera of North America. Pri-
vately published by the author. Available from Am.
Arachnol. Soc.

Stadelbacher, E. A., and T. C. Lockley. 1983. The spiders of
Geranium dissectum Linneaus in Washington County,
Mississippi. I. Georgia Entomol. Soc. 18: 398-402.

Sterling, W. L., A. Dean, and N. Abd El-Salam. 1992.
Economic benefits of spider (Araneae) and insect
(Hemiptera: Miridae) predators of cotton fleahoppers.
I. Econ. Entomol. 85: 52-57.

Sterling, W. L., K. M. El-Zik, and L. T. Wilson. 1989.
Biological control of pest populations. In Integrated
pest management systems and cotton production.
Frisbie, El-Zik, and Wilson (eds.). Iohn Wiley, New

York, pp. 155-189.

Young, O. P., and G. B. Edwards. 1990. Spiders in United
States field crops and theirpotentialeffecton crop pests.
I. Arachnol. 18: 1-27.

Edited by R. Marie Iones
Cover design by Roxy A. Pike
Department of Agricultural Communications

Mention 0t a trademark or a proprietary product does not
constitute a guarantee or a warranty of the product by The
Texas Agricultural Experiment Station and does not imply its

approval to the exclusion of other products that also may be

suitable.

All programs and information of The Texas Agricultural Ex-
periment Station are available to every one without regard to
race, color, religion, sex, age, handicap, or national origin.

Copies printed: 1,000