Oecologia (1991) 88:289 295 Oecologia 9 Springer-Verlag 1991 Effects of rutin-fed caterpillars on an invertebrate predator depend on temperature N.E. Stamp, T. Erskine, and C.J. Paradise* Department of Biological Sciences, State University of New York, Box 6000 Binghamton,NY 1390~6000, USA Received January 31, 1991 / Accepted in revised form June 19, 1991 Summary. A factorial experiment examined the effects of varying concentrations of the allelochemical rutin in cat- erpillars and the length of time the caterpillars had fed on the behavioral interactions of predatory stinkbugs ( Podisus maculiventris) and their prey (Manduca sexta). Diet had no significant effect on defensive behavior of the caterpillars. The length of time that the caterpillars had fed (1 vs. 24 h) only influenced the frequency of cater- pillars knocking the attacking stinkbugs away, with cat- erpillars knocking the stinkbugs away more often after 24 h of feeding. A second experiment tested the effects of diet (prey fed various concentrations of rutin), tem- perature (18 ~ C and 28 ~ C) and gender on consumption and growth parameters of fifth instar stinkbugs. At the cooler temperature, the bugs ate more, gained more weight but took twice as long to complete the stadium and consequently had reduced relative consumption and relative growth rates. Diet had no significant effect on biomass gained or stadium duration, but rutin-fed cater- pillars did depress the stinkbugs' relative consumption rates. The effect of food quality on relative growth rate (RGR) was temperature dependent; rutin had no signifi- cant effect at the cooler temperature, but a high dose of rutin reduced RGR at the warmer temperature. Rutin had a greater negative impact on the females than the males. The effect of rutin on these predators was different than the effect on their prey (this study compared to Stamp (1990, 1992)) : the negative effects of rutin seem to impact on the stinkbug's growth rather than on molting. Key words: Predator-prey interactions - Temperature Allelochemicals - Manduca sexta Podisus maculiventris Plant allelochemicals ingested by caterpillars may affect the interactions of caterpillars and their natural enemies * Current address." Department of Biology, Pennsylvania State University, UniversityPark, PA 16802, USA Offprint requests to: N. Stamp (reviewed by Barbosa and Saunders 1985; Barbosa 1988 ; Bernays and Graham 1988). Specialist caterpillars are less palatable to invertebrate predators than are general- ist caterpillars (Bernays 1988; Bernays 1989; Bernays and Cornelius 1989). In some cases, this reduced palat- ability results in deterrence upon contact or after biting (Bernays 1988). Although there is some evidence that specialist insect herbivores may be less reactive to attack than generalists (Bernays 1988; Bernays and Cornelius 1989), caterpillar defensive behavior varies considerably (Marston et al. 1978) and may depend in part on the type of predator (Stamp and Bowers 1988). Caterpillars of the same species fed different diets or with and without gut contents may differ in their palatability to invertebrate predators (Bernays and Cornelius 1989). Because the herbivore's diet may influence both the herbivore's de- fense and the predator's offense as well as acceptance of prey, the herbivore's diet may affect the rate of prey consumed by and thus the growth rate of the predator. Therefore, studies examining the effects of plant al- lelochemicals in herbivorous prey on the consumption and growth rates of predators would have more ex- planatory power with inclusion of an assessment of the effects of the prey's diet on the behavioral interactions of prey and their predators. However as yet, whether diet influences defensive behavior of insect herbivores is un- known. Nonetheless, specialist caterpillars are often eaten by invertebrate predators (e.g., Mukerji and LeRoux 1965; McPherson 1980; Stamp and Bowers 1988). Although invertebrate predators tend to be generalists and may avoid prey containing allelochemicals that may have adverse effects on them, invertebrate predators may often eat such prey because the predators are naive, are hungry (Paradise and Stamp 1991), can selectively feed on prey parts (e.g., hemolymph, Baker 1926), or are able to de- toxify allelochemicals (Yu 1987). Several studies have shown that specific alMochemicals in host caterpillars prolong developmental time, reduce final size and lower survivorship of parasitoids (Thurston and Fox 1972; Campbell and Duffey 1979; Barbosa and Saunders 1985;