An Unlikely Beginning: A Fortunate Life.

Elizabeth A. Bernays grew up in Australia and studied at the University of Queensland before traveling in Europe and teaching high school in London. She later obtained a PhD in entomology at London University. Then, as a British government scientist, she worked in England and in developing countries on a variety of projects concerned with feeding by herbivorous insects and their physiology and behavior. In 1983, she was appointed professor at the University of California, Berkeley, where her research expanded to a variety of topics, all related to the physiology, behavior, and ecology of feeding in insects. She was awarded a DSc from the University of London, and at about the same time became head of the Department of Entomology and regents' professor at the University of Arizona. In Arizona, most of her research involved multiple approaches to the understanding of diet breadth in a variety of phytophagous insect species.

Insect defences: taste alteration and endoparasites.

Taste sensation and food selection by animals can change adaptively in response to experience, for example to redress specific nutrient deficiencies. We show here, in two species of caterpillar, that infection by lethal parasites alters the taste of specific phytochemicals for the larvae. Given that these compounds are toxic to the parasites and are found in plants eaten by the caterpillars, their changed taste may encourage parasitized caterpillars to increase consumption of plants that provide a biochemical defence against the invaders.

Antagonistic effects of floral scent in an insect-plant interaction.

In southwestern USA, the jimsonweed Datura wrightii and the nocturnal moth Manduca sexta form a pollinator-plant and herbivore-plant association. Because the floral scent is probably important in mediating this interaction, we investigated the floral volatiles that might attract M. sexta for feeding and oviposition. We found that flower volatiles increase oviposition and include small amounts of both enantiomers of linalool, a common component of the scent of hawkmoth-pollinated flowers. Because (+)-linalool is processed in a female-specific glomerulus in the primary olfactory centre of M. sexta, we hypothesized that the enantiomers of linalool differentially modulate feeding and oviposition. Using a synthetic mixture that mimics the D. wrightii floral scent, we found that the presence of linalool was not necessary to evoke feeding and that mixtures containing (+)- and/or (-)-linalool were equally effective in mediating this behaviour. By contrast, females oviposited more on plants emitting (+)-linalool (alone or in mixtures) over control plants, while plants emitting (-)-linalool (alone or in mixtures) were less preferred than control plants. Together with our previous investigations, these results show that linalool has differential effects in feeding and oviposition through two neural pathways: one that is sexually isomorphic and non-enantioselective, and another that is female-specific and enantioselective.

Effects of experience on palatability hierarchies of novel plants in the polyphagous grasshopperSchistocerca americana.

We studied the influence of diet composition and breadth on the subsequent acceptability of three novel plants to sixth instarSchistocerca americana. Rearing diets of equal breadth differing in composition, and diets differing in breadth, significantly altered first meal length on some but not all of the test plants. These effects on palatability altered and at times reversed the palatability hierarchy of insects reared on different diets. The effects of rearing insects on broad diets were not produced by exposure to the plant odors alone, but apparently required contact with a diversity of plants while feeding. Switching diets for 24 h prior to testing did not alter preferences induced by rearing diets. The relationship of these patterns to induced preferences in other insects, and some possible mechanisms for generating induced preferences, are discussed.

Relative nutritional quality of C3 and C4 grasses for a graminivorous lepidopteran, Paratrytone melane (Hesperiidae).

We tested the hypothesis that C4 grasses are inferior to C3 grasses as host plants for herbivorous insects by measuring the relative performance of larvae of a graminivorous lepidopteran, Paratrytone melane (Hesperiidae), fed C3 and C4 grasses. Relative growth rates and final weights were higher in larvae fed a C3 grass in Experiment I. However, in two additional experiments, relative growth rates and final weights were not significantly different in larvae fed C3 and C4 grasses. We examined two factors which are believed to cause C4 grasses to be of lower nutritional value than C3 grasses: foliar nutrient levels and nutrient digestibility. In general, foliar nutrient levels were higher in C3 grasses. In Experiment I, protein and soluble carbohydrates were digested from a C3 and a C4 grass with equivalent efficiencies. Therefore, differences in larval performance are best explained by higher nutrient levels in the C3 grass in this experiment. In Experiment II, soluble carbohydrates were digested with similar efficiencies from C3 and C4 grasses but protein was digested with greater efficiency from the C3 grasses. We conclude (1) that the bundle sheath anatomy of C4 grasses is not a barrier to soluble carbohydrate digestion and does not have a nutritionally significant effect on protein digestion and (2) that P. melane may consume C4 grasses at compensatory rates.

Self-medication as adaptive plasticity: increased ingestion of plant toxins by parasitized caterpillars.

Self-medication is a specific therapeutic behavioral change in response to disease or parasitism. The empirical literature on self-medication has so far focused entirely on identifying cases of self-medication in which particular behaviors are linked to therapeutic outcomes. In this study, we frame self-medication in the broader realm of adaptive plasticity, which provides several testable predictions for verifying self-medication and advancing its conceptual significance. First, self-medication behavior should improve the fitness of animals infected by parasites or pathogens. Second, self-medication behavior in the absence of infection should decrease fitness. Third, infection should induce self-medication behavior. The few rigorous studies of self-medication in non-human animals have not used this theoretical framework and thus have not tested fitness costs of self-medication in the absence of disease or parasitism. Here we use manipulative experiments to test these predictions with the foraging behavior of woolly bear caterpillars (Grammia incorrupta; Lepidoptera: Arctiidae) in response to their lethal endoparasites (tachinid flies). Our experiments show that the ingestion of plant toxins called pyrrolizidine alkaloids improves the survival of parasitized caterpillars by conferring resistance against tachinid flies. Consistent with theoretical prediction, excessive ingestion of these toxins reduces the survival of unparasitized caterpillars. Parasitized caterpillars are more likely than unparasitized caterpillars to specifically ingest large amounts of pyrrolizidine alkaloids. This case challenges the conventional view that self-medication behavior is restricted to animals with advanced cognitive abilities, such as primates, and empowers the science of self-medication by placing it in the domain of adaptive plasticity theory.