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Life Cycles and Food Plants Maier, C.T., C.R. Lemmon, J.M. Fengler, D.F. Schweitzer, and R.C. Reardon. 2004. Caterpillars on the Foliage of Conifers in the Northeastern United States. FHTET-2004-1. Morgantown, WV: USDA Forest Service, Forest Health Technology Enterprise Team; 151 p. Moths and butterflies (Order Lepidoptera) whose caterpillars consume the foliage of northeastern conifers have an enormous diversity of life styles. Most species have one or two generations per year. They develop through four life stages: the egg, the caterpillar or the larva, the pupa (chrysalis in butterflies), and the adult (moth or butterfly). In Lepidoptera, the caterpillar and the adult usually are markedly different in appearance and function. The caterpillar principally feeds and grows, whereas the adult mainly reproduces and disperses. The transformation from the caterpillar to the adult moth or butterfly takes place during the pupal stage. Most of the species that are restricted to conifers spend the winter as an egg, a caterpillar, or a pupa; very few species pass the winter as an adult. Lepidoptera differ in the duration of their life stages. In the Northeast, the stage that exists during the late fall and winter typically lasts the longest because development slows or stops during periods of low temperature. Eggs that are laid during the spring and the early summer usually hatch in 1 to 3 weeks. After hatching from eggs, caterpillars feed for variable amounts of time, but most reach full size within 1 to 3 months. Most caterpillars molt or "shed their skin" four to six times. Between molts the caterpillar is considered an instar, with the number of the instar increasing with age. Caterpillars can grow because the body covering or cuticle increases in size with each successive molt. Pupae that do not delay development normally yield adults in 1 to 4 weeks. In general, caterpillars restricted to conifers eat species in only one to a few genera. Perhaps, the most restricted in diet are the tiny caterpillars that exclusively mine needles to obtain food for development. Most of the needleminers eat trees in only one genus and sometimes in only one species of that genus. Among the larger caterpillars on pines, certain species of Macaria (Family Geometridae) and Zale (Family Noctuidae) are restricted to one or more pines, Pinus species. A narrow diet also can be found among caterpillars that eat other types of conifers. Even among the conifer feeders, however, a few species will eat the majority of native species growing within their distributional range. In New England, where our sampling was concentrated, there are 16 native species of conifers in three plant families. These families and species are: Pinaceae (firs, pines, spruces, and relatives) Balsam fir, Abies balsamea Taxaceae (yews) Canadian yew, Taxus canadensis Cupressaceae (cedars, false cedars, and junipers) Atlantic white-cedar, Chamaecyparis thyoides We generally do not list non-native food plants of caterpillars mentioned in this guide, although exotic conifers found in plantations, in yards, or along roads may be suitable food. We did not collect caterpillars on Canadian yew or creeping juniper, and infrequently sampled those in natural stands of black spruce, jack pine, and red pine. In addition, we did not sample or list native food plants that are absent or scarce to the north of southern New Jersey or Delaware. Examples of these include shortleaf pine, Pinus echinata, pond pine, P. serotina, loblolly pine, P. taeda, Virginia pine, P. virginiana (Pinaceae), and bald cypress, Taxodium distichum (Taxodiaceae). |
Forest Pests: Insects, Diseases & Other Damage Agents |
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