1 Despite considerable interest in the impacts of forest-defoliating insects and pesticide-based suppression of defoliator outbreaks on non-target arthropods, studies have often been hampered by the unpredictability of outbreaks. 2 We evaluated the long-term impacts of forest defoliation by gypsy moths, and the suppression of their outbreaks with Bacillus thuringiensis var. kurstaki (Btk), on native moths. Three years after a gypsy moth outbreak, moth diversity and abundance were compared among sites that were defoliated but not sprayed with Btk (defoliated sites), defoliated and sprayed (Btk sites) or neither (undisturbed sites). We conducted separate evaluations of the effects of disturbance history on the overall moth community, taxonomic subgroups (families) and moths differing in their dietary overlap with gypsy moths. 3 Analyses of the full moth community revealed no effects of disturbance history on local ( ) moth diversity or diversity of moths among sites ( -diversity). The -or -diversities of moths classified by their dietary overlap with gypsy moths (overlapping, partially overlapping, not overlapping) were also not affected by disturbance history. However, taxonomic affiliation was important. Geometridae -diversity in late summer was significantly lower in defoliated sites than in Btk or undisturbed sites. No effects of disturbance history on moth abundances were found. 4 We conclude gypsy moth defoliation had negative effects on a major moth family (Geometridae), although Btk application may have protected Geometridae from the adverse effects of gypsy moth defoliation. The results of the present study help to clarify the relative, and sometimes countervailing, effects of defoliators and microbial pesticides on forest communities.

Many caterpillars exhibit patterns of ultraviolet (UV) fluorescence, although its purpose is unclear. We used realistic plasticine models of a fluorescing caterpillar species, the Polyphemus moth, Antheraea polyphemus (Lepidoptera; Saturniidae), adorned with fluorescent paint treatments and unpainted controls to quantify bird predation in two hardwood forested regions of New York State, United States of America. In separate field studies, significantly more birds struck deployed model caterpillars that had no UV fluorescence. More strikes on unpainted and clear paint treatments suggest paint itself did not impact predation, whereas similar predation attempts on bird and human-visible fluorescent dummies suggest that UV fluorescence and not UV reflectance was responsible for the observed effect. A second study found the dummy’s location on the tree was also important, but the low number of bird strikes limited analyses. Although our results do not identify a mechanism, fluorescence may function to deter or avoid predation. Our study contributes to a growing body of work investigating the importance of UV patterns in arthropods and highlights a potentially fruitful area of future research on predator–prey relations.

To date, research on the effects of forest defoliator outbreaks and pesticide applications to suppress these outbreaks on non‐target forest arthropods has generally focused on non‐target Lepidoptera and has not examined effects on regional diversity. In this study, we assessed the effects of forest defoliation by gypsy moths and application of the microbial pesticide Bacillus thuringiensis var. kurstaki (Btk) to suppress gypsy moth populations on the species richness and (Shannon index) diversity of beetles in Shenandoah National Park, Virginia. In addition, we examined how these disturbances affected overall beetle abundance and abundances within different feeding guilds (herbivore, predator, fungivore, or xylophage). Three years after a gypsy moth outbreak, beetles were sampled four times throughout spring and summer at 15 sites belonging to one of three disturbance histories: undisturbed, defoliated, or sprayed with Btk. Beetles were captured using blacklight traps and then sorted to family and morphospecies. We did not detect significant effects of defoliation or Btk on local species richness (α richness) or local diversity (α diversity) of beetles. However, defoliated sites had lower β richness, i.e., lower heterogeneity in beetle species composition among sites, in early summer than sites that were undisturbed or sprayed with Btk. Overall beetle abundance was lower in spring at sites sprayed with Btk, but not significantly different among disturbance histories in other seasons. Further, effects of disturbance history on abundance were not significantly different among feeding guilds. Though the local (α) richness and diversity of beetles were not significantly influenced by gypsy moth defoliation or Btk, the reduced spatial heterogeneity of species composition (lower β richness) in defoliated areas suggests gypsy moth outbreaks could adversely affect regional species richness (γ richness). Our findings additionally suggest that Btk may protect against negative effects of gypsy moth defoliation on the regional species richness of beetles.

Ash (Fraxinus spp.) is in rapid decline across the northeastern USA due to the invasive emerald ash borer (Agrilus planipennis Fairmaire). Three recently co-occurring confamilial species may serve as alternative larval host plants for ash-reliant Lepidoptera. These prospective hosts are nonnative shrubs often planted in managed suburban landscapes and are sometimes invasive or naturalized in North America. Given the imminent decline of ash trees, we considered potential downstream effects on insect herbivores historically specialized on ash foliage. We measured the performance of three ash-specialist hawkmoths (Lepidoptera: Sphingidae) on native white ash (Fraxinus americana L.) and alternative host plants: common lilac (Syringa vulgaris L.), weeping forsythia [Forsythia suspensa (Thunb.) Vahl], and European privet (Ligustrum vulgare L.). We found the nonnative host plants provided varied support for larval survival to pupation, with biomass and growth rate affected differently by both plant and insect identity. Nearly all caterpillars reared on one alternative host, European privet, exhibited distinct malformations of the wing buds at pupation. Given caterpillar presence on privet in the field, privet may constitute an ecological trap (i.e., when female moths select a sub-optimal host, offspring survival and fitness are reduced). This work demonstrates how performance testing can reveal species-specific effects of host plant loss on mono- or oligophagous insects. For some ash specialists, alternative nonnative host plants may be suboptimal, but some cultivated host plants may be able to support certain specialist insects during native host decline. We suggest that landscaping decisions can be tailored to support threatened insect species.