Distribution. Bean leafroller is a tropical species, but apparently is a native to the southeastern United States. It is found throughout Florida and in coastal areas from South Carolina west to eastern Texas. It also invades most of the southeastern states, even attaining New England during warm years, and regu larly invades the southernmost areas of the Southwest. It cannot tolerate prolonged freezing temperatures, however, and in the United States it persists only in the southern coastal plain, perhaps only southern Florida. The range of bean leafroller also includes Mexico, Central America and the Caribbean, and south to Argentina.
A closely related species, Urbanus dorantes Stoll, has expanded its range from the tropical Americas to include the permanent range of U. proteus in the United States. Found throughout Florida, and southern Texas and Arizona, it is readily confused with bean leafroller, particularly because it also feeds on legumes, including bean (Heppner, 1975). Thus far, however, it is not particularly abundant. (See color figure 21.)
Host Plants. Bean leafroller feeds exclusively on legumes, and normally is found inhabiting open, disturbed habitats. Vegetable hosts include cowpea, lima bean, pea, and snap bean. Other hosts include soybean; wisteria, Wisteria sp.; trefoil, Desmodium spp.; butterfly pea, Clitoria spp.; and hog peanut, Amphi-carpa bracteata.
Natural Enemies. Natural enemies are poorly documented. Wasp and fly parasitoids were observed in Colombia (van Dam and Wilde, 1977). Two tachi-nids with a very wide-host range, Lespesia aletiae (Riley) and Nemorilla pyste (Walker), have been reported from bean leafroller (Arnaud, 1978). In Florida, Chrysotachina alcedo (Loew) (Diptera: Tachinidae) was reared from larvae, and predation was observed by a Polistes sp. wasp (Hymenoptera: Vespidae) and Euthyrhynchus floridanus (Linnaeus) stink bugs (Hemi-ptera: Pentatomidae). Also, a nuclear polyhedrosis virus was found to infect and to kill up to 40-50% of larvae late in the season when larvae were numerous (Temerak et al, 1984).
Life Cycle and Description. The bean leafroller can complete its life cycle in about 30 days during warm weather. They breed in southern Florida throughout the year, but are relatively infrequent in northern Florida until June, and only become abundant late in the season, usually September-October. The number of generations is not known, but has been estimated at 3-4 in Florida. In the northern areas invaded during the summer months there usually is only a single generation. In Florida, large numbers of adults are frequently observed migrating southward in the autumn (Balciunas and Knopf, 1977); they make a similar northward migration in the spring and summer, but it is less apparent.
Initially the larva is yellowish with a brownish-black head and prothoracic shield, and this general color pattern is maintained though the markings become more distinct as the larva matures, and the larva may also acquire considerable green color. With the molt to the second instar the dorsal surface of the insect is marked with numerous small black spots. Beginning with the third instar, lateral yellow lines become quite distinct. The last two instars are similar to the preceding: brownish-black head, black prothor-acic shield, yellowish body sprinkled with black spots but lighter below, and yellow lateral lines. Also evident are orange spots on the head near the base of the mandibles, and red on the ventral portion of the thoracic segment. The body tapers sharply toward both the anterior and posterior ends. Perhaps the most striking attribute of this insect, but a character shared with other members of the family Hesperiidae, is the greatly enlarged head, which is connected to the body by a narrow "neck." (See color figure 96.)
This insect has not been well studied. The most complete description was provided by Quaintance (1898a), but Young (1985) provided valuable observations. Phenology and developmental biology were given byGreene (1970a, 1971a). Greene (1970b) made reference to culture on standard bean-based artificial diet, but the relative success of this approach is not clear.
Larvae are defoliators, feeding only on leaf tissue of legumes. Greene (1971b) determined that larvae consumed about 0.5, 1.3, 5.1, 26.1, and 162.4 sq cm of foliage during instars 1-5, respectively. Beans can tolerate up to about 30% leaf loss without reduction in yield, so Greene estimated that about 4.4 larvae must complete their development on a "typical" bean plant with 2175 sq cm of foliage to inflict a damaging level of defoliation. As about one-half of the individuals perish in each life stage, Greene estimated that densities of
140 eggs or 70 first instar larvae per plant must occur to cause damage.
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