Northeastern Naturalist 782 M.J. Chips, et al. 22001155 NORTHEASTERN NATURALIST 2V2(o4l). :2728,2 N–7o9. 74 The Indirect Impact of Long-Term Overbrowsing on Insects in the Allegheny National Forest Region of Pennsylvania Michael J. Chips1,*, Ellen H. Yerger2, Arpad Hervanek1, Tim Nuttle2,3, Alejandro A. Royo4, Jonathan N. Pruitt1, Terrence P. McGlynn5, Cynthia L. Riggall5, and Walter P. Carson1 Abstract - Overbrowsing has created depauperate plant communities throughout the eastern deciduous forest. We hypothesized these low-diversity plant communities are associated with lower insect diversity. We compared insects inside and outside a 60-year-old fenced deer exclosure where plant species richness is 5x higher inside versus outside. We sampled aboveground and litter insects using sweep nets and pitfall traps and identified specimens to family. Aboveground insect abundance, richness, and diversity were up to 50% higher inside the fenced exclosure versus outside. Conversely, litter insect abundance and diversity were consistently higher outside the exclosure. Community composition of aboveground insects differed throughout the summer (P < 0.05), but litter insects differed only in late summer. Our results demonstrate that the indirect effects of long-term overbrowsing can reduce aboveground insect diversity and abundance, and change composition even when plant communities are in close proximity. Introduction The extirpation of Canis lupus L. (Gray Wolf) and Puma concolor L. (Cougar) combined with lax deer management have caused Odocoileus virginianus (Zimmermann) (White-tailed Deer) to become overabundant throughout the eastern deciduous forest, often creating structurally simple and depauperate understory plant communities (Côté et al. 2004, McCabe and McCabe 1997, Ripple et al. 2010). This scenario is particularly true in the Allegheny National Forest region of Pennsylvania where decades of overbrowsing have reduced understory plant diversity by as much as 50–75% (Banta et al. 2005, Carson et al. 2014, Goetsch et al. 2011, Kain et al. 2011, Rooney and Dress 1997) and caused the formation of recalcitrant understory layers (sensu Royo and Carson 2006) dominated by a few unpalatable species that are inimical to biodiversity recovery (Royo and Carson 2006, Royo et al. 2010). While the deleterious impact of overbrowsing on forest understories is well known (Côté et al. 2004, Rooney and Waller 2003, Waller 2014), the cascading 1Department of Biological Sciences, University of Pittsburgh, A234 Langley Hall, Pittsburgh, PA 15260. 2Department of Biology, Indiana University of Pennsylvania, 114 Weyandt Hall, Indiana, PA 15705. 3Ecological Services Division, Civil and Environmental Consultants, Inc., 333 Baldwin Road, Pittsburgh, PA 15205. 4USDA Forest Service Northern Research Station, Forestry Sciences Lab, PO Box 267, Irvine, PA 16329. 5Department of Biology, California State University Dominguez Hills, Carson, CA. *Corresponding author - mjc119@pitt.edu Manuscript Editor: Daniel Pavuk Northeastern Naturalist Vol. 22, No. 4 M.J. Chips, et al. 2015 783 effects that browsing has on arthropod communities are less clear. It is predicted that depauperate understories dominated by browse-tolerant plant species will cascade up trophic levels to lower the abundance and diversity of arthropod groups (Hunter and Price 1992, Siemann et al. 1998, Stewart 2001). This cascade may be driven by losses of both structural complexity and food-resource diversity (Stewart 2001). Alternatively, arthropods may simply track plant abundance and thus be somewhat buffered from declines in host-plant diversity (Siemann 1998, Siemann et al. 1998). To date, studies within the eastern deciduous forest have focused almost entirely on arthropods in the litter layer and have found that overbrowsing indirectly decreases arthropod abundance with variable effects on diversity (Bressette et al. 2012, Brousseau et al. 2013, Christopher and Cameron 2012, Greenwald et al. 2008, Lessard et al. 2012). Oddly, these studies have overlooked aboveground arthropod communities inhabiting the understory (but see Brousseau et al. 2013) or were hampered by small sample sizes (e.g., Bressette et al. 2012). Studies within other forest types in the southwestern United States (Huffman et al. 2009), on islands in the Pacific Northwest (Allombert et al. 2005), and in forests in Europe (Baines et al. 1994, Suominen et al. 2003) have all found that overbrowsing causes decreases in aboveground arthropod richness. If this is a typical response, overbrowsing could be a serious threat to ecosystem services. Arthropods are principal pollinators, seed dispersers, predators, decomposers, and herbivores, and account for the majority of the animal biomass in ecosystems throughout the world (Handel et al. 1981, Wilson 1987, Wise 1993). Here, we compared arthropod communities within a 60-year-old deer exclosure to an adjacent reference site in the Allegheny National Forest region of Pennsylvania. This is the oldest known deer fence in the eastern deciduous forest. The understory vegetation inside the fenced plot is composed of a diverse layer of forbs, shrubs, and saplings, while the vegetation directly outside, and in much of this region, is depauperate, structurally simple, and often dominated by a single, highly productive fern species, Dennstaedtia punctilobula (Michx.) T. Moore (Hay- Scented Fern; Carson et al. 2014, Goetsch et al. 2011, Kain et al. 2011). We tested the hypothesis that long-term deer overbrowsing indirectly decreases the diversity and richness of insects as well as changes insect community composition. Field-Site Description We conducted this study within the Allegheny high plateau region of north-central Pennsylvania on State Game Lands #30 (McKean County, 41°38'N, 78°19'W), which is part of the Hemlock–Northern Hardwood Association (Whitney 1990). Further descriptions of the region’s natural history can be found in Bjorkbom and Larson (1977) and Hough and Forbes (1943). Deer have overbrowsed this region, as well as much of Pennsylvania, since the 1930s (Carson et al. 2014, Horsley et al. 2003, Redding 1995). Northeastern Naturalist 784 M.J. Chips, et al. 2015 Vol. 22, No. 4 Methods We compared insect communities between a 0.4-ha plot surrounded by a wellmaintained deer fence (height: 2.1 m, mesh size: 15 cm x 20 cm) versus a nearby reference site (~75 m x 55 m). The fence was erected in the late 1940s and excludes White-tailed Deer, but the mesh is likely large enough to allow in smaller vertebrates such as Marmota monax (L.) (Woodchuck; Chips et al. 2014). The exclosure and reference site were exactly the same ones used by Goetsch et al. (2011) and Kain et al. (2011) to evaluate the long-term impact of browsing on the understory and overstory, respectively (see Stout 1998 for further details). The overstory of each site was 60–80 years old and characterized in decreasing order of abundance by Prunus serotina Ehrh. (Black Cherry), Acer saccharum Marshall (Sugar Maple), Fagus grandifolia Ehrh. (American Beech), Acer rubrum L. (Red Maple), and Betula spp. (birch) (Kain et al. 2011). A diverse and abundant group of wildflowers and shrubs characterized the understory vegetation inside the fenced plot versus the adjacent reference site (percent plant cover: inside exclosure = 63.42 ± 6.10; reference site = 9.28 ± 1.55, P < 0.05; mean species richness: inside exclosure = 6.2; reference site = 1.1, P < 0.05; Goetsch et al. 2011). Many of these wildflowers peak in abundance in May prior to canopy closure in late spring. A single species, Hay-scented Fern, dominated the reference site and also dominates understories throughout much of the entire region (Carson et al. 2014, Goetsch et al. 2011, Hill and Silander 2001, Rooney and Dress 1997, Royo et al. 2010). Hay-scented Fern is an unpalatable and fairly shade-tolerant species that peaks in biomass in mid- to late June (Hill and Silander 2001, Horsley and Marquis 1983, Horsley et al. 2003, Rooney and Dress 1997, Royo and Carson 2006). Insect sampling We sampled insects on 12 May, 29 June, and 26 August 2011 within the exclosure and in the unfenced reference site 200 m away of the same size, elevation, and slope. We sampled litter insects with pitfall traps and aboveground insects with sweep nets. On each date and throughout each site, we collected 20 sweepnet and 20 pitfall-trap samples. Sweep nets were made of fine mesh with a hoop 30 cm in diameter with a 1-m handle. We swept the top 10–30 cm of all vegetation within reach along 10-m transects starting every 10 m with respect to the 75 m edge of the plot and from random locations with respect to the 55 m edge. All sweep-net transects were at least 3 m from the fence or edge of the reference plot and at least 10 m from each other. All pitfall traps were placed within random locations at least 3 m from the fence and at least 10 m away from each other to minimize edge effects. Pitfall traps were half-liter plastic containers, 8 cm diameter x 10 cm height, filled with 2 cm of 95% ethanol. We placed the rim of the pitfall trap flush with the soil surface and collected them after 24 hours (House and Stinner 1983, Williams 1958). With the help of commonly used identification guides (Borror and White 1970, BugGuide.net, Marshall 2007), we identified all insects larger than 5 mm to family. In addition, identifications were verified at the Carnegie Museum of Natural History. Northeastern Naturalist Vol. 22, No. 4 M.J. Chips, et al. 2015 785 Statistical analyses We used univariate repeated-measures analysis of variance (RM-ANOVA; Von Ende 2001) with SAS (PROC GLIMMIX, version 9.3.1; SAS Institute, Inc., Cary, NC) to examine differences in insect abundance, richness, and exponential Shannon diversity (eH') throughout the spring and summer. We used this diversity index because it scales Shannon diversity to a comparable measure of species richness (e.g., number of species; see Jost 2006, 2007). The month of sampling was the repeated measure and the treatment was the deer fence. We treated pitfall and sweep-net sampling techniques as independent measures of arthropod communities and analyzed them separately. To assess differences in arthropod community composition, we performed permutational multivariate analysis of variance (PERMANOVA) via ADONIS using the Vegan Package (R core development team; Anderson 2001). Our experimental treatment (fenced exclosure) was not replicated and our analyses were based upon subsamples (pseudoreplicates sensu Hurlburt 1984), thus our results should be interpreted with appropriate caution (see Oksanen 2001 for a wider discussion on this issue). Nonetheless, because deer have been excluded for 60+ years, this study is quite unique. Results We found that decades of overbrowsing indirectly reduced aboveground insect abundance ~40%, richness ~45%, and diversity ~50% throughout spring and summer, but this effect was particularly strong in August (fence x time interaction: P < 0.001; Fig. 1A, B, C; Table 1). In addition, overbrowsing shifted aboveground Figure 1. Mean (± S.E.) abundance, family richness, and diversity (eH’) of insects larger than 5 mm collected in the spring and summer of 2011 in the Allegheny National Forest region of north-central Pennsylvania in sweep nets (A–C) and pitfall traps (D–F) inside a 60-year-old fenced exclosure and in a nearby reference site. Northeastern Naturalist 786 M.J. Chips, et al. 2015 Vol. 22, No. 4 insect composition over the entire sampling period, particularly in June (Fig. 2A, B, C; Table 2). This shift was primarily driven by higher counts of elaterid beetles in the reference site (19 vs. 6) and more mirid bugs inside of the fenced exclosure (2 vs. 30) (Appendix 1). In contrast, overbrowsing increased litter insect abundance by ~85%, richness by ~30%, and diversity by ~30% throughout spring and summer (Fig. 1D, E, F; Table 1). However, only in August did community composition of litter insects differ between the 2 sites (Fig. 2D, E, F; Table 2). Specifically, browsing increased the abundance of carabid beetles, chrysomelid beetles, and litter ants particularly in August (Appendix 2). Discussion Aboveground insects We found that overbrowsing caused a reduction in the abundance, richness, and diversity of aboveground insects and also changed the composition of these insect Table 2. PERMANOVA results to test for compositional differences of insects larger than 5 mm caught in sweep nets and pitfall traps in the spring and summer of 2011 in a 60-year-old deer fence and an adjacent reference site in the Allegheny National Forest region in north-central Pennsylvania. * indicates significant P-values. See Appendices 1 and 2 as well as Figure 2 for a breakdown of insect orders and families. Sweep net Pitfall trap df R2 F P df R2 F P May 1, 26 0.03 0.65 0.8335 1, 33 0.05 1.66 0.1265 June 1, 36 0.11 4.17 0.0010* 1, 36 0.04 1.40 0.2170 August 1, 34 0.05 1.65 0.0815 1, 31 0.10 3.50 0.0145* Overall 1, 98 0.03 2.89 0.0005* 1, 102 0.02 1.83 0.1045 Table 1. Mixed-model ANOVA results to test for differences in abundance, family richness, and diversity (eH’) of insects larger than 5 mm caught in sweep nets and pitfall traps in the spring and summer of 2011 within a 60-year-old fenced exclosure and a nearby reference site in the Allegheny National Forest Region in north-central Pennsylvania. * indicates significant P-values. See Figure 1 for all fence x time interactions. Abundance Richness Diversity (eH’) df F P df F P df F P Fence Sweep Net 1, 114 8.23 0.0049* 1, 114 14.77 0.0002* 1, 114 16.26 0.0001* Pitfall Trap 1, 114 10.73 0.0014* 1, 114 4.82 0.0301* 1, 114 3.95 0.0492* Time Sweep Net 2, 114 5.43 0.0056* 2, 114 7.14 0.0012* 2, 114 7.46 0.0009* Pitfall Trap 2, 114 6.68 0.0018* 2, 114 0.75 0.4768 2, 114 0.79 0.4564 Fence x time Sweep Net 2, 114 3.50 0.0334* 2, 114 5.27 0.0065* 2, 114 5.74 0.0042* Pitfall Trap 2, 114 0.11 0.8965 2, 114 0.21 0.8140 2, 114 0.31 0.7374 Northeastern Naturalist Vol. 22, No. 4 M.J. Chips, et al. 2015 787 communities. These reductions and changes were likely caused by the depauperate nature of the understory vegetation that occurred in the reference site versus the rich understory layer that occurred inside the exclosure. Indeed, the general reduction of herbivorous hemipteran insects (Miridae) drove much of this decline across the sampling period (Appendix 1). Our results may apply broadly because overbrowsing has caused the formation of a depauperate understory plant community throughout the region (Carson et al. 2014) and elsewhere (Royo and Carson 2006, Waller 2014). Our findings are consistent with the impact of ungulate browsers on aboveground insects in lowland rainforests in the Pacific Northwest, European woodlands, boreal forests, and Ponderosa forests (Allombert et al. 2005, Baines et al. 1994, Brousseau et al. 2013, Huffman et al. 2009). While results varied throughout spring and summer (Fig. 1A, B, and C), the overall signal was that long-term deer overabundance caused a decline in the diversity, richness, and abundance of aboveground insects and significantly changed arthropod community composition. Peaks in arthropod abundance and richness later in the season in the reference site may be attributed to high percent cover of Hay-scented Fern, which reaches peak frond density in June and July followed by senesce in August (Hill and Silander 2001). Though we know very little about insect associations with Hay-scented Fern (Balick et al. 1978), high frond density may create a favorable habitat for understory insects in June (e.g., Elaterid beetles; Fig. 2B, Appendix 1). Arthropod abundance is known to track plant abundance rather than plant diversity Figure 2. Percent relative abundance in the fenced exclosure (Fence) and reference site at each sampling date in 2011 for both sweep nets in (A) May, (B) June, and (C) August, and pitfall trap samples for (D) May, (E) June, and (F) August. Aboveground insect communities were significantly different throughout the summer, but particularly in June and litter insect communities were significantly different only in August (see Table 2). See Appendices 1 and 2 for the relative abundance of each insect family. Northeastern Naturalist 788 M.J. Chips, et al. 2015 Vol. 22, No. 4 in other community types, particularly grasslands (Siemann 1998, Siemann et al. 1998), and dense host concentrations cause increases in insect herbivore abundance (Long et al. 2003, Root 1973). Litter insects Overbrowsing increased litter insect richness, abundance, and diversity throughout the sampling period and led to changes in insect community composition only in late summer. Increases in the absolute abundance of predatory ground beetles as well as ants likely drive these changes. Our findings build upon previous studies in North America and Europe, which documented that the indirect effects of overbrowsing led to increases in the absolute abundance of predatory ground beetles (Brousseau et al. 2013, Melis et al. 2006). The mechanism by which browsing increases the abundance of particular litter insects is unclear, but is likely caused by increased temperatures and lower humidity in the litter layer because of decreased plant cover (Stewart 2001). Specifically, browsers likely create environments favorable to arthropods adapted for high-light, dry environments (Gonzalez-Megias et al. 2004, Melis et al. 2006, Suominem et al. 2003). In contrast, some studies found that overbrowsing causes declines in litter arthropod abundance and diversity via an increase in vulnerability to avian predators and changes in soil nutrients (Bressette et al. 2012, Wardle et al. 2001). Conclusions We found that aboveground insect richness, abundance, and diversity were higher and insect species composition different inside a >60-year-old deer exclosure versus a nearby reference site. The sharply contrasting understory plant communities that occurred in each site likely caused these differences. In contrast, we found higher abundance, richness and diversity of litter insects in an area exposed to browsing. Our results, and the results of others, call for large-scale, well-replicated experiments that evaluate not only the impact of overbrowsing on arthropod abundance but also how these may subsequently alter entire food webs in the understory as well as in forest canopies over long time scales. We are aware of only one White-tailed Deer exclosure of this advanced age; therefore deer refugia (e.g., tall boulders) could substitute for very old deer exclosures in this approach (Banta et al. 2005, Chollet et al. 2013, Comisky et al. 2005, Rooney 1997). We suggest that differences in the arthropod communities could cascade further up the food chain and impact the abundance and diversity of higher trophic levels, particularly avian insectivores (e.g., Nuttle et al. 2011). Acknowledgments Special thanks to R. Androw, R. Davidson, and J. 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The history and status of the hemlock–hardwood forests of the Allegheny Plateau. Journal of Ecology 78:443–458. Williams, G. 1958. Mechanical time-sorting of pitfall captures. Journal of Animal Ecology 27:27–35. Wilson, E.O. 1987. Little things that run the world (the importance and conservation of invertebrates). Conservation Biology 1:344–346. Wise, D.H. 1993. Spiders in Ecological Webs. Cambridge University Press, Cambridge, UK. Northeastern Naturalist Vol. 22, No. 4 M.J. Chips, et al. 2015 793 Appendix 1. Mean relative abundance (± S.E.) and total count of insects larger than 5 mm caught in sweep nets in the spring and summer of 2011 in a 60-year-old deer fence and adjacent reference site in the Allegheny National Forest Region in northcentral Pennsylvania. All insects were identified to family. Sweep-net samples Order/family Treatment May June August Coleoptera Canthandae Reference 0.00 (0.00) 0.01 (0.01) 0.00 (0.00) Fence 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) Cerembycidae Reference 0.00 (0.00) 0.01 (0.01) 0.00 (0.00) Fence 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) Chrysomelidae Reference 0.11 (0.08) 0.01 (0.01) 0.00 (0.00) Fence 0.07 (0.04) 0.01 (0.01) 0.01 (0.01) Curculionidae Reference 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) Fence 0.00 (0.00) 0.01 (0.01) 0.00 (0.00) Elateridae Reference 0.00 (0.00) 0.23 (0.05) 0.00 (0.00) Fence 0.02 (0.02) 0.01 (0.04) 0.00 (0.00) Lucanidae Reference 0.11 (0.08) 0.00 (0.00) 0.00 (0.00) Fence 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) Staphylinidae Reference 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) Fence 0.02 (0.02) 0.01 (0.01) 0.01 (0.01) Diptera Anthomyiidae Reference 0.00 (0.00) 0.00 (0.00) 0.11 (0.06) Fence 0.00 (0.00) 0.01 (0.01) 0.05 (0.02) Anthomyzidae Reference 0.06 (0.06) 0.00 (0.00) 0.00 (0.00) Fence 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) Calliphoridae Reference 0.00 (0.00) 0.01 (0.01) 0.00 (0.00) Fence 0.00 (0.00) 0.00 (0.00) 0.01 (0.01) Chironomidae Reference 0.06 (0.06) 0.00 (0.00) 0.00 (0.00) Fence 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) Dolichopodidae Reference 0.06 (0.06) 0.00 (0.00) 0.00 (0.00) Fence 0.02 (0.02) 0.00 (0.00) 0.05 (0.03) Drosophilidae Reference 0.06 (0.06) 0.00 (0.00) 0.00 (0.00) Fence 0.05 (0.03) 0.00 (0.00) 0.00 (0.00) Empididae Reference 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) Fence 0.05 (0.03) 0.00 (0.00) 0.00 (0.00) Heleomyzidae Reference 0.06 (0.06) 0.00 (0.00) 0.04 (0.04) Fence 0.00 (0.00) 0.03 (0.02) 0.02 (0.01) Lauxaniidae Reference 0.00 (0.00) 0.18 (0.09) 0.11 (0.08) Fence 0.00 (0.00) 0.05 (0.02) 0.08 (0.03) Lonchaeidae Reference 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) Fence 0.02 (0.02) 0.00 (0.00) 0.00 (0.00) Micropezidae Reference 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) Fence 0.00 (0.00) 0.01 (0.01) 0.00 (0.00) Muscidae Reference 0.00 (0.00) 0.04 (0.04) 0.04 (0.04) Fence 0.00 (0.00) 0.04 (0.02) 0.04 (0.01) Mycetophilidae Reference 0.00 (0.00) 0.01 (0.01) 0.04 (0.04) Fence 0.00 (0.00) 0.04 (0.02) 0.00 (0.00) Phoridae Reference 0.06 (0.06) 0.00 (0.00) 0.00 (0.00) Fence 0.07 (0.04) 0.00 (0.00) 0.00 (0.00) Rhagionidae Reference 0.06 (0.06) 0.00 (0.00) 0.00 (0.00) Fence 0.02 (0.02) 0.00 (0.00) 0.00 (0.00) Northeastern Naturalist 794 M.J. Chips, et al. 2015 Vol. 22, No. 4 Sweep-net samples Order/family Treatment May June August Simuliidae Reference 0.11 (0.08) 0.00 (0.00) 0.00 (0.00) Fence 0.05 (0.03) 0.00 (0.00) 0.00 (0.00) Stratiomyidae Reference 0.00 (0.00) 0.01 (0.01) 0.00 (0.00) Fence 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) Syrphidae Reference 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) Fence 0.00 (0.00) 0.01 (0.01) 0.02 (0.02) Tachinidae Reference 0.00 (0.00) 0.00 (0.00) 0.04 (0.04) Fence 0.07 (0.04) 0.00 (0.00) 0.00 (0.00) Tipulidae Reference 0.00 (0.00) 0.05 (0.03) 0.00 (0.00) Fence 0.05 (0.03) 0.12 (0.04) 0.01 (0.01) Hemiptera Aphididae Reference 0.00 (0.00) 0.01 (0.01) 0.00 (0.00) Fence 0.02 (0.02) 0.00 (0.00) 0.00 (0.00) Berytidae Reference 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) Fence 0.00 (0.00) 0.00 (0.00) 0.01 (0.01) Cercopidae Reference 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) Fence 0.00 (0.00) 0.01 (0.01) 0.00 (0.00) Cicadellidae Reference 0.11 (0.08) 0.01 (0.01) 0.14 (0.07) Fence 0.07 (0.04) 0.03 (0.02) 0.09 (0.02) Membracidae Reference 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) Fence 0.00 (0.00) 0.02 (0.01) 0.04 (0.02) Miridae Reference 0.00 (0.00) 0.02 (0.02) 0.11 (0.06) Nabidae Reference 0.00 (0.00) 0.02 (0.02) 0.14 (0.08) Fence 0.02 (0.02) 0.00 (0.00) 0.16 (0.05) Pentatomidae Reference 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) Fence 0.00 (0.00) 0.00 (0.00) 0.04 (0.01) Hymenoptera Braconidae Reference 0.00 (0.00) 0.00 (0.00) 0.04 (0.04) Fence 0.02 (0.02) 0.01 (0.01) 0.01 (0.01) Formicidae Reference 0.11 (0.08) 0.00 (0.00) 0.00 (0.00) Fence 0.10 (0.04) 0.00 (0.00) 0.00 (0.00) Ichneumonidae Reference 0.00 (0.00) 0.05 (0.02) 0.14 (0.07) Fence 0.00 (0.00) 0.03 (0.02) 0.09 (0.03) Pteromalidae Reference 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) Fence 0.00 (0.00) 0.00 (0.00) 0.01 (0.01) Tenthredinidae Reference 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) Fence 0.05 (0.03) 0.05 (0.04) 0.05 (0.02) Lepidoptera Arctiidae Reference 0.00 (0.00) 0.01 (0.01) 0.00 (0.00) Fence 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) Galechiidae Reference 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) Fence 0.00 (0.00) 0.01 (0.01) 0.00 (0.00) Geometridae Reference 0.06 (0.06) 0.06 (0.02) 0.04 (0.04) Fence 0.02 (0.02) 0.00 (0.00) 0.01 (0.01) Noctuidae Reference 0.00 (0.00) 0.04 (0.02) 0.00 (0.00) Fence 0.00 (0.00) 0.02 (0.01) 0.02 (0.01) Notodontidae Reference 0.00 (0.00) 0.04 (0.02) 0.00 (0.00) Fence 0.00 (0.00) 0.00 (0.00) 0.02 (0.02) Mecoptera Panorpidae Reference 0.00 (0.00) 0.15 (0.04) 0.00 (0.00) Fence 0.00 (0.00) 0.18 (0.05) 0.00 (0.00) Northeastern Naturalist Vol. 22, No. 4 M.J. Chips, et al. 2015 795 Sweep-net samples Order/family Treatment May June August Neuroptera Hemerobiidae Reference 0.00 (0.00) 0.00 (0.00) 0.04 (0.04) Fence 0.05 (0.05) 0.00 (0.00) 0.00 (0.00) Orthoptera Acrididae Reference 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) Fence 0.02 (0.02) 0.00 (0.00) 0.00 (0.00) Psocodea Pseudocaecilidae Reference 0.00 (0.00) 0.01 (0.01) 0.00 (0.00) Fence 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) Total count Reference 18 82 28 Fence 42 106 141 Northeastern Naturalist 796 M.J. Chips, et al. 2015 Vol. 22, No. 4 Appendix 2. Mean relative abundance (± S.E.) and total count of insects larger than 5 mm caught in pitfall traps in the spring and summer of 2011 in a 60-year-old deer fence and adjacent reference site in the Allegheny National Forest Region in north-central Pennsylvania. All insects were identified to family. Pitfall-trap samples Order/family Treatment May June Aug Coleoptera Anthribidae Reference 0.03 (0.02) 0.00 (0.00) 0.00 (0.00) Fence 0.03 (0.03) 0.00 (0.00) 0.00 (0.00) Carabidae Reference 0.17 (0.10) 0.05 (0.02) 0.35 (0.08) Fence 0.24 (0.07) 0.10 (0.04) 0.11 (0.05) Chrysomelidae Reference 0.16 (0.05) 0.00 (0.00) 0.05 (0.02) Fence 0.11 (0.05) 0.00 (0.00) 0.00 (0.00) Curculionidae Reference 0.00 (0.00) 0.01 (0.01) 0.03 (0.03) Fence 0.03 (0.03) 0.00 (0.00) 0.00 (0.00) Elateridae Reference 0.06 (0.05) 0.00 (0.00) 0.00 (0.00) Fence 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) Erotylidae Reference 0.02 (0.02) 0.00 (0.00) 0.00 (0.00) Fence 0.05 (0.04) 0.00 (0.00) 0.00 (0.00) Histeridae Reference 0.02 (0.02) 0.00 (0.00) 0.00 (0.00) Fence 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) Lampyridae Reference 0.00 (0.00) 0.00 (0.00) 0.01 (0.01) Fence 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) Nitidulidae Reference 0.09 (0.05) 0.00 (0.00) 0.00 (0.00) Fence 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) Scarabacidae Reference 0.00 (0.00) 0.01 (0.01) 0.00 (0.00) Fence 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) Silphidae Reference 0.06 (0.04) 0.00 (0.00) 0.00 (0.00) Fence 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) Staphylinidae Reference 0.20 (0.07) 0.14 (0.05) 0.01 (0.01) Fence 0.24 (0.09) 0.15 (0.07) 0.08 (0.04) Tenebrionidae Reference 0.02 (0.02) 0.00 (0.00) 0.00 (0.00) Fence 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) Collembola Tomoceridae Reference 0.00 (0.00) 0.00 (0.00) 0.01 (0.01) Fence 0.00 (0.00) 0.01 (0.01) 0.00 (0.00) Diptera Anisopodidae Reference 0.02 (0.02) 0.00 (0.00) 0.00 (0.00) Fence 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) Anthomyiidae Reference 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) Fence 0.00 (0.00) 0.00 (0.00) 0.03 (0.03) Calliphoridae Reference 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) Fence 0.00 (0.00) 0.00 (0.00) 0.08 (0.04) Lauxaniidae Reference 0.00 (0.00) 0.01 (0.01) 0.00 (0.00) Fence 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) Muscidae Reference 0.00 (0.00) 0.01 (0.01) 0.01 (0.01) Fence 0.00 (0.00) 0.03 (0.02) 0.03 (0.03) Nematocera Reference 0.02 (0.02) 0.00 (0.00) 0.00 (0.00) Fence 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) Tipulidae Reference 0.00 (0.00) 0.06 (0.03) 0.01 (0.01) Fence 0.00 (0.00) 0.12 (0.05) 0.00 (0.00) Northeastern Naturalist Vol. 22, No. 4 M.J. Chips, et al. 2015 797 Pitfall-trap samples Order/family Treatment May June Aug Hemiptera Cicadellidae Reference 0.02 (0.02) 0.01 (0.01) 0.00 (0.00) Fence 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) Pentatomidae Reference 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) Fence 0.03 (0.03) 0.00 (0.00) 0.00 (0.00) Hymenoptera Formicidae Reference 0.13 (0.05) 0.69 (0.18) 0.48 (0.10) Fence 0.29 (0.11) 0.59 (0.2) 0.59 (0.15) Lepidoptera Geometridae Reference 0.00 (0.00) 0.02 (0.02) 0.01 (0.01) Fence 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) Noctuidae Reference 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) Fence 0.00 (0.00) 0.00 (0.00) 0.05 (0.04) Mecoptera Panorpidae Reference 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) Fence 0.00 (0.00) 0.00 (0.00) 0.03 (0.03) Orthoptera Gryllaeridae Reference 0.00 (0.00) 0.00 (0.00) 0.01 (0.01) Fence 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) Total count Reference 64 116 75 Fence 38 68 37