1. To understand the diversity and strength of predation in natural communities, researchers must quantify the total amount of prey species in the diet of predators. Metabarcoding approaches have allowed widespread characterization of predator diets with high taxonomic resolution. To determine the wider impacts of predators, researchers should combine DNA techniques with estimates of population size of predators using mark-release-recapture (MRR) methods, and with accurate metrics of food consumption by individuals.2. Herein, we estimate the scale of predation exerted by four damselfly species on diverse prey taxa within a well-defined 12-ha study area, resolving the prey species of individual damselflies, to what extent the diets of predatory species overlap, and which fraction of the main prey populations are consumed.3. We identify the taxonomic composition of diets using DNA metabarcoding and quantify damselfly population sizes by MRR. We also use predator-specific estimates of consumption rates, and independent data on prey emergence rates to estimate the collective predation pressure summed over all prey taxa and specific to their main prey (non-biting midges or chironomids) of the four damselfly species.4. The four damselfly species collectively consumed a prey mass equivalent to roughly 870 (95% CL 410-1,800) g, over 2 months. Each individual consumed 29%-66% (95% CL 9.4-123) of its body weight during its relatively short life span (2.1-4.7 days; 95% CL 0.74-7.9) in the focal population. This predation pressure was widely distributed across the local invertebrate prey community, including 4 classes, 19 orders and c. 140 genera. Different predator species showed extensive overlap in diets, with an average of 30% of prey shared by at least two predator species. 5. Of the available prey individuals in the widely consumed family Chironomidae, only a relatively small proportion (0.76%; 95% CL 0.35%-1.61%) were consumed. 6. Our synthesis of population sizes, per-capita consumption rates and taxonomic distribution of diets identifies damselflies as a comparatively minor predator group of aerial insects. As the next step, we should add estimates of predation by larger odonate species, and experimental removal of odonates, thereby establishing the full impact of odonate predation on prey communities. K E Y W O R D Sbarcoding, CO1, food web, insect, Odonata, predation pressure 1366 | Journal of Animal Ecology KAUNISTO eT Al.

Measures of parasitism often differ between hosts. This variation is thought due in part to age or sex differences in exposure to parasites and/or susceptibility to parasitism. We assessed how often age or sex biases in parasitism were found using a large, multiyear (2006-2017) dataset of 12 parasite species of Icelandic rock ptarmigan (Lagopus muta). We found host traits (i.e. age and/or sex) accounted for significant variation in abundance of 11 of the 12 parasite species. We often found increased abundance among juvenile hosts, although significant adult biases were observed for three parasite species. Additionally, higher levels of parasitism by many species were observed for female hosts, contrary to frequent male biases in parasitism reported for other vertebrates. Abundance of six parasite species was best explained by interactions between host age and sex; some degree of decrease in abundance with host age was present for both male and female hosts for four of those parasite species. We consider various host and parasite traits that could account for observed singular and repeated patterns of age and/or sex biases in parasitism (e.g. age-and sex-related grouping behaviours, age-specific mortality in relation to parasitism, acquisition of greater immunity with age). This work provides a foundation for future studies investigating age-related differences in acquired immunity and age-specific parasite-mediated mortality for males and females, as well as studies on interactions between co-infecting parasite species.

This chapter discusses insect behavioral responses to parasites. Dividing behaviors conceptually into those that occur before and after infection, we start by reviewing the evidence that insects identify and avoid potentially infectious environments to minimize negative consequences of infection. Behavioral responses following infection according to their adaptive value to either the insect host or to the parasite will then be considered. One section covers sickness behaviors proposed to benefit the host by conserving energetic resources during infection; another section discusses evidence for altered host behavior as a parasite adaptation enhancing parasite survival or transmission. The mechanistic link between behavior and immunity in insects is briefly discussed, and provide a summary of methods and techniques becoming standard to studying behavior of model insect species in the context of infection. The chapter concludes by discussing future directions in the study of insect behavioral responses to parasites.

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