Megalographa biloba Stephens Lepidoptera Noctuidae

Natural History

Distribution. This native insect is found throughout North and South America, including Hawaii. It is relatively infrequent, however, in western Canada and the northwestern United States. Apparently it cannot overwinter in northern latitudes and reinvades the northern United States and southern Canada each summer.

Host Plants. Bilobed looper is reported to feed on several families of plants, but only a few crops are affected. Among vegetables crops eaten are bean, cabbage, and lettuce. Other crops accepted include alfalfa, clover, and tobacco, as well as some ornamental plants such as geranium, gladiolus, ivy, and salvia. Weeds consumed include hedge nettle, Stachys sp.; sunflower, Helianthus sp.; vervain, Verbena sp.; and yellow thistle, Cirsium horridulum.

Natural Enemies. The natural enemies of bilobed looper are unknown.

Life Cycle and Description. Adults, eggs, and larvae have been found during the period of January-June in Florida, with most larvae observed in late spring (Martin et al., 1981a). Presumably they disperse northward during the spring and summer months.

  1. The eggs of bilobed looper are hemispherical in shape, white in color, and bear ridges that radiate vertically. They hatch in 3-5 days, usually during the morning hours.
  2. There are five instars, with development times of about three, two, three, three, and four days, respectively, when reared at 25°C. Total larval development time is about 13, 16, and 25 days at 30°, 25°, and 20°C, respectively. Head capsule widths for the five instars are about 0.2, 0.4, 0.7, 1.2, and 1.9 mm, respectively. The larvae attain a length of about 30 mm at maturity. In form, larvae resemble most other related loopers; the body is distinctly broader at the posterior end and tapers toward the head. The general color of the larva is green, but there is a dark green dorsal stripe, 3-4 weak white lines running parallel to the dorsal green line, and a thin white line on each side just above the lateral spiracles. The head is green, and has a strong black band on each side of the head. The thoracic legs are normally black, and three pairs of thoracic legs are present. The larva of bilobed looper is easily confused with other loopers, but because it bears black thoracic legs and black bars on the side of the head it is most easily confused with alfalfa looper, Autographa californica (Speyer). In contrast to alfalfa looper, however, bilobed looper is weakly marked with stripes, and bears microspines on the abdomen. A key to common vegetable-feeding loopers can be found in Appendix A. (See color figure 42.)
  3. Pupation occurs in a thin, nearly transparent silk cocoon that is attached to the host plant or

Bilobed looper larva.

Bilobed looper larva.

nearby vegetation. Pupae of bilobed looper are variable in color, usually mottled black with irregular tan or light green areas. Pupation requires about 6, 9, and 15 days at 30°, 25°, and 20°C, respectively. (See color figure 266.)

Adult. The wingspan of the bilobed looper moth measures about 4 cm. The forewing is irregularly marked with pale-brown to medium-brown, and a silver bilobed spot is located near the center of the wing. The hind wing is gray to tan basally and darker brown distally. The prereproductive period of the adult is estimated at 2-4 days, and the reproductive period at 5-6 days. Adults often mate more than once. Total egg production is about 500 eggs per female. Adult longevity is estimated at 8.5 days for males and 10.0 days for females. (See color figure 227.)

Developmental biology and rearing information were provided by Beach and Todd (1988). Adult and larval descriptions, and keys to differentiate bilobed looper from related species, were provided by Eichlin and Cunningham (1978), Crumb (1956), Capinera and Schaefer (1983), and Capinera (1986). Bilobed looper was also included in the key to vegetable-atttacking loopers in Appendix A.

Damage

Bilobed looper is a defoliator, and mature larvae can consume considerable quantities of foliage during the final days of larval life. However, it rarely is sufficiently abundant to be cause for concern.

Management

Moth populations can be monitored with blacklight traps. A sex pheromone component that attracts numerous noctuids in the subfamily Plusiinae, cis-7-dodecenyl acetate, also is attractive to bilobed looper

Adult bilobed looper.

(Roelofs and Comeau, 1970). Larvae are readily controlled with foliar applications of insecticides, including Bacillus thuringiensis.

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