Anyphaena (Araneae, Anyphaenidae) Overwintering on Lowest Limbs of White Oak
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2003. The Journal of Arachnology 31:40±43 ANYPHAENA (ARANEAE, ANYPHAENIDAE) OVERWINTERING ON LOWEST LIMBS OF WHITE OAK David W. Boyd, Jr.: USDA, ARS, Small Fruit Research Station, Poplarville, MS 39470 USA Will K. Reeves: Department of Entomology, Clemson University, Clemson, SC 29634 USA ABSTRACT. Juvenile Anyphaena sp. were collected from overwintering traps placed on the lowest limbs of white oak, Quercus alba, in South Carolina. Multiple regression analysis was used to determine that the number of juvenile Anyphaena sp. found can be predicted by the circumference of the limb, the distance from the trunk and the distance from the ground. This study helps demonstrate that the limbs of trees, although often neglected in overwintering studies, can provide a refuge for arthropods. Keywords: Anyphaena, overwintering, Quercus alba Many spiders enter a dormant stage during sibility. Three sets of traps were placed on winter conditions (Schaefer 1977) and those limbs greater than or equal to3minlength: that overwinter on the trunks of trees are often one trap set was proximate to the trunk, one surveyed by collecting the spiders with card- was in the middle of the limb, and one was board wrapped around tree trunks (Tamaki & on the terminus of the limb. Two sets of traps Halfhill 1968; Tedders 1974; Fye 1985; Mizell were placed on limbs shorter than 3 m in & Schiffhauer 1987; Pekar 1999; Horton et al. length: one trap set was proximate to the trunk 2001). However, the species collected in the and one on the terminus of the limb. We trunk traps are not necessarily the same spe- placed traps around the limb 2.5 cm apart, cies that are collected during warmer months parallel to the limb, and held them in place from the limbs of the same trees (PekaÂr 1999; with gray duct tape. The diameter of the limb Horton et al. 2001) and the limbs are usually determined the number of traps around the neglected when sampling for overwintering limb. Two groups of traps were place around species. Our research was conducted to deter- the limb 3±6 cm apart, one offsetting the other mine if the limbs of white oak trees, Quercus (Fig. 1). alba L., were suitable for arthropods to over- We used 5 limbs on the oak tree in Pickens winter, and, if so, where on the limbs they County, each with 3 sets of traps. On the tree overwintered. at Reedy River Historical Park in Greenville County we used three limbs, each with 2 sets METHODS of traps, and on the tree at Bob Jones Uni- We made traps of gray coroplast (corrugat- versity we used two limbs, each with 3 sets ed plastic, similar to cardboard) by cutting a of traps. We used a total of 27 traps. The num- sheet of coroplast into sections 15 cm long by ber of limbs used was based on the number 3±3.5 cm wide, providing six longitudinal of limbs reachable at each location with a 3 cavities in each trap. We placed traps on three m ladder. For purposes of regression analysis mature white oak trees, Quercus alba L., on the average circumference of the limb at each 30 October 1998. One tree was located in trap (circumference at both ends of the trap Pickens County, South Carolina on the Clem- set divided by 2), the distance of the trap from son University campus. Two trees were locat- trunk, the distance from the trap to the ground, ed in Greenville County, South Carolina, one and the branching of the limb from the trunk on the Bob Jones University campus and the to the trap were measured. The bark surface other at Reedy River Falls Historical Park. was rated on a scale of 1±3, where 1 5 Trees were selected based on ease of acces- smooth and 3 5 rough. 40 BOYD, Jr. & REEVESÐANYPHAENA OVERWINTERING ON WHITE OAK 41 Figure 1.ÐOne set of coroplast strip traps. Traps were removed 24 February 1999 after independent variables and the independent three consecutive days of average daily tem- variables. Therefore, only the raw independent peratures near freezing (61 8C) (average tem- variables were used in the analysis. Stepwise, perature for Greenville County was 0.9 8C for forward, and backward model selection tech- 22±24 Feb. and 20.4 8C for Pickens County). inques all provided the same model. The mod- Traps were placed in plastic bags, taken to the el showed no systematic patterns, no outliers, lab and placed in the freezer. Specimens were and no evidence of lack of ®t. removed from the traps, separated, preserved in 80% ethanol and identi®ed. Voucher spec- RESULTS imens were placed in the Clemson University Spiders were the most numerous arthropods Arthropod Collection. collected. All the arthropods collected are list- Juvenile Anyphaena sp. were the only ar- ed in Table 1. More Anyphaena sp. were col- thropods found in numbers large enough to lected near the trunk than the terminus of the conduct multiple regression analysis. The total limbs (Table 2). number of Anyphaena sp. collected was 340. The multiple regression analysis provide Multiple regression analysis was conducted the following model: Number of Anyphaena using Minitab. The dependent variable was sp. 5216.1 1 20.3 (circumference of limb) 2 the number of Anyphaena, which was stan- 2.74 (distance from the trunk) 1 9.86 (dis- dardized for each trap set by dividing the total tance from the ground). This model, with an number of Anyphaena by the total number of R2 of 70.0%, shows that the number of Any- traps in each set. The independent variables phaena overwintering in traps on the bottom were average circumference of the limb, dis- limbs of Q. alba can be predicted by the cir- tance from the trunk, distance from the cumference of the limb, the distance from the ground, number of branches per limb, and trunk and the distance from the ground. bark surface scale for each trap set. For multiple regression analysis on Any- DISCUSSION phaena no transformation of the dependent Schaefer (1977) studied the overwintering variable was needed. A tolerance test showed habits of spiders and determined four over- multicolinearity between polynomials of the wintering habit types. Anyphaena sp. is part 42 THE JOURNAL OF ARACHNOLOGY Table 1.ÐArthropods collected from overwintering traps around limbs of white oak. Class Order Family Species Arachnida Araneae Agelenidae Coras sp. juv. Anyphaenidae Anyphaena sp. juv. Araneidae Araneus sp. juv. Philodromidae Philodromus vulgaris (Hentz) Philodromus sp. juv. Salticidae Eris militaris (Hentz) Hentzia mitrata (Hentz) Metacyrba undata (De Geer) Thomisidae Bassaniana versicolor (Keyserling) Diplopoda Polyxenida Polyxenidae Polyxenus fasiculatus (Say) Insecta Blattaria Blattellidae Parcoblatta sp. juv. Diptera Syrphidae Syrphus sp. juv. Hemiptera Miridae Deraeocoris nebulosus (Uhler) Psocoptera Ectopsocidae Ectopsocus meridionalis Ribaga of the majority (45%) of spiders that over- after leaf-fall spiders move down from the winter in the juvenile stage (Schaefer 1977). crown until they ®nd refuge (Duffey 1969; Tree-dwelling spiders in the genus Anyphaena Horton et al. 2001), which might be the case are nocturnal wanderers, typically living in fo- with our spiders. The overwintering traps pro- liage from spring through fall, but little of vided a refuge that otherwise would not have their ecology or behavior is known (Platnick been available. The diameter of the limbs af- 1974). They feed on aphids and other prey not fected the number of spiders and without ex- typically active during the day (Marc & Ca- ception, the larger the diameter of the branch nard 1997; Marc et al. 1999). Anyphaena spp. the rougher the bark, which might also pro- take refuge during the winter but can be active vide refugia. during warmer days (Turnbull 1960), increas- Horton et al. (2001) collected arthropods ing their ability for survival (Gunnarsson from cardboard bands weekly 23 Aug±07 Dec 1985). Other overwintering studies, that in- 1999 in Washington apple and pear orchards. cluded Anyphaena spp., sampled only the They found Anyphaena paci®ca Banks in trunk or the proximal end of the largest higher numbers (224 total) on a weekly basis branch. Bajwa and AliNiazee (2001) found than in overwintering samples (7 total, col- only four Anyphaena in a four year study. lected in Jan 2000). They suggested that the Horton et al. (2001) found only seven Any- spiders overwinter elsewhere. In Oregon, A. phaena in a one year study. We demonstrated paci®ca was found in low numbers (0.35% of that Anyphaena will overwinter on most parts total catch) during the growing season by of the branches with refugia present. beating the branches over a net (Bajwa & Most refuges available to overwintering AliNiazee 2001). In Europe, Marc et al. spiders are eliminated when leaves are shed. (1999) and Marc and Canard (1997) suggested Previous studies have shown or suggested that that A. accentuata (Walckenaer) overwinters on the tree trunk, but they collected very few Table 2.ÐMean number of Anyphaena sp. juv. individuals (1% of total catch). (6 SE) collected from coroplast traps on white oak, Our study provides information that can be Quercus alba limbs (South Carolina, 1999). Limb used in further studies of overwintering ar- position is relative to the trunk. thropods on trees. The branches represent a large portion of the tree and are often neglect- Limb Average # ed as a sampling site during the winter position Anyphaena (n) months. Large numbers of spiders on the Proximate 17.4 6 2.0 (10) limbs could alter decision made in integrated Middle 12.3 6 2.8 (10) pest management for landscapes and orchards Terminus 5.4 6 1.3 (8) such as apple, peach, pear, and pecan.