A Color Key to the Common Spiders Found in Alfalfa and Cotton in New Mexico
D.B. Richman, Science Specialist
J. Drake, Adjunct Assistant Professor
T. Carrillo, Senior Research Specialist
C.S. Bundy, Assistant Professor
J.J. Ellington, Professor
Department of Entomology, Plant Pathology and Weed Science
College of Agriculture, Consumer and Environmental Sciences, New Mexico State University.
A color key to spiders found in alfalfa and cotton in New Mexico is presented. Color digital photographs are placed at every couplet to aid in identifying specific morphological features. It is hoped that keys similar to the present one will allow non-specialists in the future to evaluate the beneficial complexes in their systems. Keys of this type should allow the lay person to make reasonably accurate identifications.
Spiders have been collected and identified in the alfalfa and cotton fields of New Mexico, over the last 20 years, from the Mesilla Valley, Doña Ana County. Richman et al. (1990) outlined the fauna of alfalfa and compared it with faunas in New York, Virginia, Kentucky and California (Wheeler 1973, Howell & Pienkowski 1971, Culin and Yeargan 1983 a-c, Yeargan and Dondale 1974). Breene et al. (1993) published a review of spiders in Texas cotton fields. This publication included a picture key, utilizing published illustrations from various sources. There have been no publications on cotton spiders of New Mexico, but there was a preliminary presentation of the current study including the Doña Ana County fauna at an informal symposium prior to a national meeting of the Entomological Society of America (New Orleans, La., Dec. 2, 1990).
Whitcomb et al. (1963), Riechert and Lockley (1984), and Young and Edwards (1990) have all indicated that spiders are important predators in most, if not all, agricultural systems. Mansour (1987) indicated that spiders can control such pests in cotton as the Egyptian leaf worm. A more recent study by Riechert and Bishop (1990) in vegetable plots provides the best evidence that spiders can limit pest populations. Most recently, Wise (1993) summarized the literature on the impact of spiders on insect populations and called for more studies because some research seemed to be contradictory. Some problems in determining the role of spiders in agroecosystems in current and past research include documenting functional spider/prey responses, and the broad range of spider predatory habits and possible competition with and/or predation on other biological control agents. The general consensus seems to be that spiders, especially certain guilds of spiders, are important in limiting populations of certain pests, but that other guilds or species may actually be detrimental to other beneficials or neutral to pest species. This result should not be especially surprising because the system is basically indifferent to human activities. That the community of natural enemies functions as well as it does to limit pest most of the time is remarkable.
The majority of spiders collected in alfalfa and cotton in the Mesilla Valley were Pardosa sternalis (Thorell), Misumenops celer (Hentz), Misumenops coloradensis Gertsch, Grammonota cf. pictilis O.P. Cambridge and Tetragnatha laboriosa Hentz. These made up 95% of 3,473 spiders collected in alfalfa fields (Richman et al. 1990). The species of Misumenops and Misumenoides can probably be considered neutral or perhaps even harmful as they habitually wait to ambush prey on flower heads. They would thus be likely to capture many pollinators and parasitic Hymenoptera. The rest, especially the lycosid and linyphiid spiders (Pardosa, Erigone and Grammonota, among others), are probably beneficial. Pardosa sternalis is a hunting spider that actively searches for prey and may find more of the abundant pest species because of this trait. Grammonota and Erigone may build small sheet webs and may capture many tiny insects, especially aphids and leafhoppers, but little is known about their role in agroecosystems. Tetragnatha is an orb-weaver that can actually have an impact on pest insects, especially on aphid and mosquito populations (Provencher and Coderre 1987, Dabrowska-Prot and Luczak 1968). Thus three of the five most abundant spiders in alfalfa and cotton are probably beneficial in most (but probably not all) cases.
The following key was developed to allow the researcher, student and the farmer or agricultural agent to identify the spiders known or suspected to occur in alfalfa and cotton agroecosystems in the Mesilla Valley without recourse to the technical literature. It is hoped that with familiarity, the beneficial species will be recognized and that their roles in biological control will be evaluated to provide a more solid foundation for management decisions. Spiders, however, do not exist in a vacuum. All of the mortality factors, including spiders, insect predators, parasitoids, diseases, and weather conditions, need to be evaluated and placed in the context of treatment expense and crop value before control decisions are made. Even so, the “footsteps of the farmer” are the ultimate necessity in any agricultural situation.
How to Use the Key
The following key has been developed to facilitate the identification of common spiders in the alfalfa and cotton agroecosystems. This key should work well in all cotton and alfalfa growing areas, in the southern parts of New Mexico. We have tried to reduce terminology and to define terms when it is necessary. We are also including a speed key, which should help break down the possibilities before starting with the color key. Photographs of specimens should aid greatly in understanding the key.
|If the spider has enlarged chelicerae (mouthparts) and six eyes arranged in a partial circle (sowbug-eating spiders) see figs. 7-9||Dysderidae|
|If the spider has enlarged anterior median eyes (jumping spiders) see fig. 17||Salticidae|
|If the spider has enlarged posterior median eyes (wolf spiders) see fig. 51||Lycosidae|
|If the spider was found on an orb (wheel-shaped) web (orb-weavers)
see figs. 3-4, 46, 55-56, 62, 67, 72-73
|If the spider was found in a space (tangled) or tiny sheet web
see figs. 5-6, 57-58, 63-66, 68-71
|If the spider has normal legs, eight eyes in two eye rows, and no prey capture web (may be found in silken, resting retreats or with egg sac) (sac and ground spiders) see figs. 26-27, 40-43||Anyphaenidae, Miturgidae,
Corinnidae or Gnaphosidae
|If the spider has laterigrade legs (first three pairs flattened and facing forward) and no web (crab spiders) see figs. 32-33, 35-39||Thomisidae
|If the spider has two rows of spines of different lengths on the front legs and feeds on other spiders (pirate spiders) see figs. 12-13||Mimetidae|
|If the spider has six of its eight eyes arranged in a circlet (lynx spiders)
see figs. 53-54
A Color Key to the Common Spiders Found in Alfalfa and Cotton in New Mexico
|1a. Spiders with a cribellum (sieve plate) (fig. 1) in front of spinnerets on venter; females and most males with calamistrum (comb) (fig. 2) on fourth metatarsus||2|
|1b. Spiders without cribellum or calamistrum||3|
||Uloborus sp. (ULOBORIDAE
or ORB-WEAVING CRIBELLATE SPIDERS)
||Dictyna spp. (DICTYNIDAE
or TINY SPACE-WEB WEAVERS)
|DYSDERIDAE or SOWBUG-EATING SPIDERS (NOTE: This European introduction is usually found with sowbugs and may have a mildly venomous bite.)|
||Mimetus sp. (MIMETIDAE or PIRATE SPIDERS)|
(SALTICIDAE or JUMPING SPIDERS)
(Peckham & Peckham)
Peckham & Peckham
||Sassacus vitis (Cockerell)|
||Hibana incursa (Chamberlin) (ANYPHAENIDAE)|
Philodromus sp. (PHILODROMODAE)
& Misumenoides formosipes
|| (MITURGIDAE & CORINNIDAE
or SAC SPIDERS)
or GROUND SPIDERS
– many genera and species)
|| Agelenopsis spp.
and Hololena hola (Chamberlin) (AGELENIDAE or FUNNELWEB-WEAVERS)
|| Pardosa sternalis (Thorell)
or WOLF SPIDERS)
|NOTE: Also Hogna carolinensis Walckenaer and other genera and species, mostly larger in size than Pardosa.|
||Oxyopes salticus (Hentz)
||Tetragnatha laboriosa Hentz (TETRAGNATHIDAE)|
||Latrodectus hesperus Chamberlin & Ivie (WESTERN BLACK WIDOW)|
|(NOTE: This spider has a powerful neurotoxin venom and should not be handled.) Fig. 65 shows a juvenile female.)|
||other Theridiidae e.g. Steatoda sp. (Comb-footed spiders)|
|(NOTE: None of these are these are considered dangerous.)|
||Erigone sp. cf. aletris Crosby and Bishop|
||Grammonota sp. cf. pictilis O. P.-Cambridge|
|24a. With distinctive bar on underside (fig. 72)||Metepeira sp.|
|24b. With distinctive spots on underside (fig. 73)||Neoscona oaxacensis (Keyserling)|
Breene, R.G., D.A. Dean, M. Nyffler and G.B. Edwards. 1993. Biology, predation ecology, and significance of spiders in Texas cotton ecosystems with a key to the species. Bull, Texas A. &M. Exp. Stn. B-1711:1-115.
Culin, J.D., and K.V. Yeargan. 1983a. Spider fauna of alfalfa and soybean in Central Kentucky. Trans. Ky. Acad. Sci. 44:40-45.
Culin J.D. and K.V. Yeargan. 1983b. Comparative study of spider communities in alfalfa and soybean ecosystems: Foliage-dwelling spiders. Ann. Entomol. Soc. Amer. 76:825-831.
Culin J.D. and K.V. Yeargan 1983c. Comparative study of spider communities in alfalfa and soybean ecosystems: Ground-surface spiders. Ann. Enotmol. Soc. Amer. 76:832-838
Dabrowski-Prot, E., and J. Luczak. 1968. Studies on the incidence of mosquitoes in the food of Tetragnatha montana Simon and its food activity in the natural habitat. Ekologia Polska-Seria A 16:843-854.
Howell, J.O., and R.L. Pienkowski. 1971. Spider populations in alfalfa, with notes on spider prey and effect of harvest. J. Econ. Entomol. 64:163-168.
Mansour, F. 1987. Spiders in sprayed and unsprayed cotton fields in Israel, their interactions with cotton pests and their importance as predators of the Egyptian cotton leaf worm, Spodoptera littoralis. Phytoparasitica 15:31-41.
Provencher, L., and D. Coderre. 1987. Functional responses and switching of Tetragnatha laboriosa Hentz (Araneidae: Tetragnathidae) and Clubiona pikei Gertsch (Araneae: Clubionidae) for the aphids Rhopalosiphum maidis (Fitch) and Rhopalosiphum padi (L.) (Homoptera: Aphididae). Environ. Entomol. 16:1305-1309.
Richman, D.B., J.J. Ellington, K.R. Kiser and G. Ferguson-Faubion. 1990. A comparison of a New Mexico alfalfa spider fauna with eastern and California faunas. Southwest Entomol. 15:387-397.
Riechert, S.E., and L. Bishop. 1990. Prey control by an assemblage of generalist predators: spiders in garden test systems. Ecology 71:1441-1450.
Riechert, S.E., and T. Lockley. 1984. Spiders as biological control agents. Ann. Rev. Entomol. 29:299-320.
Wheeler, A.G. Jr. 1973. Studies in the arthropod fauna of alfalfa. V. Spiders (Araneida). Can. Entomol. 105:425-432.
Whitcomb, W.H. 1974. Natural populations of entomophagous arthropods and their effect on the agroecosystem, pp. 150-169. In, F.G. Maxwell and F.A. Harris. ed. Proceedings of the Summer Institute on Biological Control of Plant Insects and Diseases, Stoneville, Mississippi.
Whitcomb, W.H., H. Exline and R.C.Hunter. 1963. Spiders of the Arkansas cotton field. Ann. Entomol. Soc. Amer. 56:653-660
Wise, D.H. 1993. Spiders in ecological webs. Cambridge Univ. Press, New York, 328p.
Yeargan, K.V. and C.D. Dondale. 1974. The spider fauna of alfalfa fields in Northern California. Ann. Entomol. Amer. 67:681-682.
Young, O.P. and G.B. Edwards. 1990. Spiders in United States field crops and their potential effect on crop pests. J. Arachnol. 18:1-27.
Spider Figures (1-73)
|Figure 1||Figure 2|
|Figure 3||Figure 4|
|Figure 5||Figure 6|
|Figure 7||Figure 8|
|Figure 9||Figure 10|
|Figure 11||Figure 12|
|Figure 13||Figure 14|
|Figure 15||Figure 16|
|Figure 17||Figure 18|
|Figure 19||Figure 20|
|Figure 21||Figure 22|
|Figure 23||Figure 24|
|Figure 25||Figure 26|
|Figure 27||Figure 28|
|Figure 29||Figure 30|
|Figure 31||Figure 32|
|Figure 33||Figure 34|
|Figure 35||Figure 36|
|Figure 37||Figure 38|
|Figure 39||Figure 40|
|Figure 41||Figure 42|
|Figure 43||Figure 44|
|Figure 45||Figure 46|
|Figure 47||Figure 48|
|Figure 49||Figure 50|
|Figure 51||Figure 52|
|Figure 53||Figure 54|
|Figure 55||Figure 56|
|Figure 57||Figure 58|
|Figure 59||Figure 60|
|Figure 61||Figure 62|
|Figure 63||Figure 64|
|Figure 65||Figure 66|
|Figure 67||Figure 68|
|Figure 69||Figure 70|
|Figure 71||Figure 72|
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Printed and electronically distributed April 2006, Las Cruces, NM.