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1. Broadening the ecology of fear: non-lethal effects arise from diverse responses to predation and parasitism

   https://doi.org/10.1098/rspb.2020.2966  

   Daversa, D. R.; Hechinger, R. F.; Madin, E.; Fenton, A.; Dell, A. I.; Ritchie, E. G.; Rohr, J.; Rudolf, V. H.; Lafferty, K. D. (February 2021, Proceedings of the Royal Society B: Biological Sciences)

   null (Ed.)

   Research on the ‘ecology of fear’ posits that defensive prey responses to avoid predation can cause non-lethal effects across ecological scales. Parasites also elicit defensive responses in hosts with associated non-lethal effects, which raises the longstanding, yet unresolved question of how non-lethal effects of parasites compare with those of predators. We developed a framework for systematically answering this question for all types of predator–prey and host–parasite systems. Our framework reveals likely differences in non-lethal effects not only between predators and parasites, but also between different types of predators and parasites. Trait responses should be strongest towards predators, parasitoids and parasitic castrators, but more numerous and perhaps more frequent for parasites than for predators. In a case study of larval amphibians, whose trait responses to both predators and parasites have been relatively well studied, existing data indicate that individuals generally respond more strongly and proactively to short-term predation risks than to parasitism. Apart from studies using amphibians, there have been few direct comparisons of responses to predation and parasitism, and none have incorporated responses to micropredators, parasitoids or parasitic castrators, or examined their long-term consequences. Addressing these and other data gaps highlighted by our framework can advance the field towards understanding how non-lethal effects impact prey/host population dynamics and shape food webs that contain multiple predator and parasite species. 

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2. Artificial light at night increases top-down pressure on caterpillars: experimental evidence from a light-naive forest

   https://doi.org/10.1098/rspb.2023.0153  

   Deitsch, John F.; Kaiser, Sara A. (March 2023, Proceedings of the Royal Society B: Biological Sciences)

   Artificial light at night (ALAN) is a globally widespread and expanding form of anthropogenic change that impacts arthropod biodiversity. ALAN alters interspecific interactions between arthropods, including predation and parasitism. Despite their ecological importance as prey and hosts, the impact of ALAN on larval arthropod stages, such as caterpillars, is poorly understood. We examined the hypothesis that ALAN increases top-down pressure on caterpillars from arthropod predators and parasitoids. We experimentally illuminated study plots with moderate levels (10–15 lux) of LED lighting at light-naive Hubbard Brook Experimental Forest, New Hampshire. We measured and compared between experimental and control plots: (i) predation on clay caterpillars, and (ii) abundance of arthropod predators and parasitoids. We found that predation rates on clay caterpillars and abundance of arthropod predators and parasitoids were significantly higher on ALAN treatment plots relative to control plots. These results suggest that moderate levels of ALAN increase top-down pressure on caterpillars. We did not test mechanisms, but sampling data indicates that increased abundance of predators near lights may play a role. This study highlights the importance of examining the effects of ALAN on both adult and larval life stages and suggests potential consequences of ALAN on arthropod populations and communities. 

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3. Crowdsourced online images provide insights into predator-prey interactions of putative natural enemies

   https://doi.org/10.1016/j.fooweb.2019.e00126  

   Hernandez, Madison; Masonick, Paul; Weirauch, C. (January 2019, Food webs)

   Most megadiverse clades of insects are herbivores, but several large radiations consist almost entirely of predators. Their species numbers make comprehensive direct observations of predator-prey interactions difficult to obtain. Citizen science approaches are increasingly utilized to harvest ecological data for organisms including insects. We use crowdsourced images documenting predator-prey interactions of assassin bugs (Hemiptera: Reduviidae), a speciose clade of predatory insects, to (1) determine the breakdown of assembled online images by geographic region and reduviid subfamily; (2) evaluate if the accumulated images provide new insights into prey diversity; and (3) assess evidence for taxa that feed on pest species, pollinators, and engage in intraguild predation. Photographs were assembled (n = 832) and resulted in an image database that included representatives of 11 subfamilies; most records belonged to diurnal Harpactorinae and Phymatinae, but some subfamilies with poorly understood prey diversity were also documented. Taxa with substantial image representation of prey (21–242 predation events) showed significant overlap with prey reported in the literature. A high percentage of images for Apiomerus Hahn and Phymata Latreille documented predation events on native and non-native bees; percentages varied widely among species of Zelus Fabricius. Arilus cristatus (Linnaeus) was documented to prey on several pest species, with little evidence for pollinator predation. Potential effects of these natural enemies on pollinators and intraguild predators should be further investigated, providing important insights into mechanisms influencing community structure and ecosystems processes. 

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4. Video surveillance reveals a community of largely nocturnal Danaus plexippus (L.) egg predators

   https://doi.org/10.1007/s10841-020-00248-w  

   Myers, Andrew T.; Haan, Nathan L.; Landis, Douglas A. (May 2020, Journal of Insect Conservation)

   Monarch butterfly (Danaus plexippus L.) declines in eastern North America have prompted milkweed host plant restoration efforts in non-agricultural grasslands. However, grasslands harbor predator communities that exert high predation pressure on monarch eggs and larvae. While diurnal monarch predators are relatively well known, no studies have investigated the contribution of nocturnal monarch predators. We used video cameras to monitor sentinel monarch eggs and fourth instars on milkweed in southern Michigan to identify predators and determine if nocturnally-active species impose significant predation pressure. We observed ten arthropod taxa consuming monarch eggs and larvae, with 74% of egg predation events occurring nocturnally. Taxa observed attacking monarch eggs included European earwigs (Forficula auricularia L.), tree crickets (Oecanthus sp.), lacewing larvae (Neuroptera), plant bugs (Miridae), small milkweed bugs (Lygaeus kalmii Stal), ants (Formicidae), spiders (Araneae: Salticidae and other spp.), harvestmen (Opiliones), and velvet mites (Trombidiformes: Trombidiidae). Larvae were attacked by ground beetles (Calleida sp.), jumping spiders (Araneae: Salticidae), and spined soldier bugs (Podisus maculiventris Say). Our findings provide important information about monarch predator-prey interactions that could be used to develop strategies to conserve monarchs through reducing predation on early life stages. 

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5. Reducing Native Ant Abundance Decreases Predation Rates in Midwestern Grasslands

   https://doi.org/10.1093/ee/nvz127  

   Wills, B D; Kim, T N; Fox, A F; Gratton, C; Landis, D A; Redak, Richard (November 2019, Environmental Entomology)

   Abstract Diverse and robust predator communities are important for effective prey suppression in natural and managed communities. Ants are ubiquitous components of terrestrial systems but their contributions to natural prey suppression is relatively understudied in temperate regions. Growing evidence suggests that ants can play a significant role in the removal of insect prey within grasslands, but their impact is difficult to separate from that of nonant predators. To test how ants may contribute to prey suppression in grasslands, we used poison baits (with physical exclosures) to selectively reduce the ant population in common garden settings, then tracked ant and nonant ground predator abundance and diversity, and removal of sentinel egg prey for 7 wk. We found that poison baits reduced ant abundance without a significant negative impact on abundance of nonant ground predators, and that a reduction in ant abundance decreased the proportion of sentinel prey eggs removed. Even a modest decrease (~20%) in abundance of several ant species, including the numerically dominant Lasius neoniger Emery (Hymenoptera: Formicidae), significantly reduced sentinel prey removal rates. Our results suggest that ants disproportionately contribute to ground-based predation of arthropod prey in grasslands. Changes in the amount of grasslands on the landscape and its management may have important implications for ant prevalence and natural prey suppression services in agricultural landscapes. 

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