Abstract. The ability of predators to reduce prey populations is generally ascribed to the consumption of prey individuals. However, predators may also induce behavioral changes in prey individuals, which can reduce prey survival and reproduction. Pea aphid populations are impacted by a variety of predators, many of which induce escape responses in individual aphids. We created disturbance-only predators (surgically manipulated predators that were unable to consume prey, but were still able to forage and interact with prey) and measured their ability to suppress aphid population growth over a six-day period. The greatest reduction in aphid population growth was caused by normal predators that were able to both consume and disturb aphids, but aphid population growth was also strongly reduced by nonconsumptive, disturbance-only predators. These field experiments are the first to show that predators reduce prey population growth partly through predator-induced changes in prey behavior, as well as through consumption of prey individuals.

For more than 80 years, ecologists have debated whether reproduction by female insect herbivores and parasitoids is constrained by the time needed to find hosts (time limitation) or by the finite supply of mature eggs (egg limitation). Here we present the first direct measures of permanent time limitation and egg limitation and their influences on the cost of oviposition and lifetime reproduction for an insect in nature. We studied the gall midge Rhopalomyia californica, which neither matures nor resorbs eggs during the adult stage. By sampling females soon after their death and correcting for predation effects, we demonstrate that females lay a large proportion of their total complement of eggs (multiyear mean: 82.9%). The egg supplies of 17.1% of females were completely exhausted, with the remaining 82.9% of females being time limited. As predicted by theory, we estimate that even though egg limitation is a minority condition within the population, egg costs make a substantial contribution (57% of the total) to the cost of oviposition. We conclude that insect life histories evolve to produce a balanced risk of time and egg limitation and, therefore, that both of these constraining factors have important influences on insect oviposition behavior and population dynamics.

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The majority of public aquaria have at least one very large tank (>370,000 liters, 100,000 gallons) as part of their collection. The large water volumes can make treatment difficult when pathogens escape quarantine or cross contamination occurs. The cost and methods of dispersion of chemotherapeutics to control infectious agents (bacterial, protozoal, or metazoan) can be prohibitive in large volumes. Currently there are few treatments for stenohaline monogeneans in large aquaria that are efficacious, safe, and affordable. This case demonstrates the safety and efficacy of a decade long use of prolonged hyposalinity that replaced the repeated use of copper and organophosphate treatments to control a Neobenedenia spp. monogenean infestation. The use of prolonged 20 ppt saline water is safe for a list of species traditionally listed as stenohaline which makes altering salinity a useful tool in treating parasites with restricted saline tolerances.