With so many species restricted by oviposition behaviors that result in a low carrying capacity in the environment, how is it that many species have escaped such limitation? Why are we plagued with so many pests in agriculture, horticulture, and forestry? One easy answer is that humans desire high-yielding, vigorous growth on their plants and exert considerable effort in growing plants ideal for insect herbivores. Big stems, leaves, buds, shoots, flowers, and fruits developed on nutritious soils with a reliable water supply result from good husbandry and suit the needs of humans and other herbivores alike. Any specialist insect herbivore requiring large, rapidly developing plant modules for oviposition and larval food will discover a cornucopia of such parts in an agricultural field or a managed forest, especially where monocultures are prevalent. Thus, many species that we would predict to be limited by resources find a bonanza of high-quality modules because of our expert husbandry. In a wild landscape, meager growth and spotty distribution of host plants would set the carrying capacity for insect herbivores orders of magnitude lower than in managed croplands, gardens, and forests.

But, there are many pests that have been outbreak species before landscapes were severely modified by humans. For example, growth-ring analysis of host trees in eastern Canada indicated episodes of heavy spruce budworm (Choristoneura fumiferana) defoliation back into the 1700s (Blais 1958, 1962, 1965), and sediments from Maine, bear abundant microlepidopteran head capsule fossils back to more than 10 000 years before the present (Anderson et al. 1986).