Distribütion. This insect is found throughout the United States and southern Canada. Its range also extends south through Central America to South America. Apparently it is absent from the Caribbean.
Host Plants. The caterpillar stage of gray hair-streak feeds on the widest array of plants of any butterfly, but few are crop plants. Serious damage is limited to bean and cotton. Because of its injury to the latter plant, this species is also known as "cotton square borer." Vegetable crops eaten include cowpea, lima bean, okra, pea, and snap bean. This insect is sometimes associated with such field crops as alfalfa, hops, lespedeza, and sweet clover. Numerous other plants are consumed by this insect, including such Leguminocae as Astragalus, Casia, Desmodium, Lupinus, and Trifolium spp.; such Malvaceae as Hibiscus, Malva, and Sphaeralcea spp.; such Polygonaceae as Eriogonum, Polygonum and Rumex spp; and many others. Although the preferred habitat is open areas inhabited by early successional plants and shrubs, most agricultural weeds are exempt from attack by this insect. Scott (1986) provided a list of larval hosts. Adults collect nectar from goldenrod, Solidago spp.; dogbane, Apocy-num spp.; milkweed, Asclepias spp.; sweet clover, Meli-lotus spp.; and other flowering plants (Opler and Krizek, 1984). (See color figure 32.)
Natural Enemies. Natural enemies generally are effective at suppression of gray hairstreak numbers, so little crop damage occurs. In Texas, for example, the first generation is abundant, but in subsequent generations caterpillars tend to be less and less abundant as parasitoids take a toll. The most important parasitoid is a gregarious species, Apanteles thecloe Riley (Hymenoptera: Braconidae). This species attacks the caterpillar, with larvae emerging from the host to pupate in white silken cocoons on the back of the caterpillar. Other, less important parasitoids are Octosmicra sp. (Hymenoptera: Chalcididae), Aplomya theclarum (Scudder), and Lespesia sp. (both Diptera: Tachinidae). Predators are poorly known, but adults are taken by robber flies (Diptera: Asilidae).
Life Cycle and Description. There are two generations annually in the northern portion of gray hair-streak's range, and 3-4 generations in the central and southern states. About 40 days are required for a complete generation. In Texas, butterflies are observed in all months except December and January. The winter is passed in the pupal stage. Females begin oviposition in February or March in the south, but not until May in the North.
tually grow to measure 12-16 mm long and 4.56.5 mm wide. Initially the larvae are slender, but with each succeeding molt the larva becomes relatively broader, so at maturity it is rather stout. The caterpillar in all instars is covered with stout hairs or bristles. The body color is generally green, but sometimes brownish. Larvae normally feed on the leaf surface during the first three instars, and thereafter display a tendency to bore into pods or other reproductive tissues. (See color figure 97.)
A comprehensive treatment of gray hairstreak biology was given by Reinhard (1929).
Foliage consumption by early instar larvae is insignificant, but damage may occur as larvae burrow into
bean or okra pods. On beans, larvae often burrow only partially into the pod, then move to another location, which may be on the same or another pod. Only in home gardens is this damage likely to be significant.
These insect cause only incidental damage and infrequently require suppression. Foliar insecticides are generally very effective.
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