Conium maculatum L. (Apiaceae), or poison hemlock, is an invasive plant native to Europe that has become extensively naturalized throughout North America. This species contains piperidine alkaloids, including coniine and γ-coniceine, that are highly toxic to vertebrates. C. maculatum was relatively free from herbivores in North America until the accidental introduction 30 yr ago of its monophagous European associate Agonopterix alstroemeriana (Clerck) (Lepidoptera: Oecophoridae). At present, A. alstroemeriana is widespread across the United States, and in some areas, such as the Northwest, can inflict substantial damage on its host plant, leading to desiccation and death. A. alstroemeriana has been used in recent years for the biological control of C. maculatum, although its use has been limited by the availability of larvae, which are field-collected from early to mid-spring, and by the lack of available information about its life history and feeding habits. Here we describe a laboratory-rearing protocol incorporating a simulated winter to induce diapause and a semidefined artificial diet that allows the production of multiple generations per year and enabled us to determine the number and duration of A. alstroemeriana developmental stages. The development of the artificial diet also permitted studies of preference and performance of A. alstroemeriana in relation to hostplant chemistry. Rearing A. alstroemeriana on artificial diet supplemented with 1.5% DW coniine had no adverse impact on ultimate instar growth or performance. In a feeding behavior assay, the presence of coniine in the diet increased A. alstroemeriana consumption three-fold relative to control diet. This behavioral response contrasts dramatically with that of Agonopterix clemensella, a native Apiaceae specialist that does not use C. maculatum as a host; of 30 larvae tested, 29 fed exclusively on diets lacking supplemental coniine. The rearing protocol and artificial diet presented here can facilitate further studies of ecological and evolutionary responses of C. maculatum after its reassociation with a coevolved herbivore in North America.