BEHAVIOR Interspecific Mating of Introduced, Sterile Bactrocera dorsalis with Wild B. carambolae (Diptera: Tephritidae) in Suriname: a Potential Case for Cross-Species Sterile Insect Technique D. O. MCINNIS, 1 P. RENDON, 2 E. JANG, 3 A. VAN SAUERS-MULLER, 4 R. SUGAYAMA, 5 AND A. MALAVASI 6 Ann. Entomol. Soc. Am. 92(5): 758Ð765 (1999) ABSTRACT Copulation with sperm transfer was observed between the oriental fruit ßy, Bactrocera dorsalis (Hendel), and the carambola fruit ßy, B. carambolae (Drew & Hancock), in outdoor Þeld cages in Suriname. Sterilized oriental fruit ßies from Hawaii were shipped to Suriname for testing against wild carambola fruit ßies to investigate whether the oriental fruit ßy could be used in a potential sterile insect program against the carambola fruit ßy. Of 217 total observed copulations on 5 test dates, 17 (7.8%) were interspeciÞc, and 10 (4.6%) were of the crucial type, sterile oriental fruit ßy   wild carambola fruit ßy . InterspeciÞc copulations tended to be of short duration, especially when the male was an oriental fruit ßy (i.e., average time in copula was 148.0 min for carambola fruit ßy   oriental fruit ßy , whereas only 4.67 min for oriental fruit ßy   carambola fruit ßy  at a 5:1 oriental fruit ßy:carambola fruit ßy ratio). Homogamic (like with like) pairings tended to be longer, especially for carambola fruit ßy, with average times in copula of 115.7 and 481.4 min for oriental fruit ßy   oriental fruit ßy  and carambola fruit ßy   carambola fruit ßy , respectively. With both sexes present, oriental fruit ßies began mating earlier in the evening (2,500-lux), whereas carambola fruit ßies started mating at 300 lux. With only sterile male oriental fruit ßies released, the proportion of interspeciÞc pairs (oriental fruit ßy   carambola fruit ßy ) rose to 1 ∕3 of the total, at a sterile : wild  ratio of 5:1. This was 3-fold higher than for the release of bisexual oriental fruit ßy. An index of mating isolation, relative isolation index, was high (100, where random mating = 1) because of high assortative mating in the case of bisexual oriental fruit ßy. Approximately 70% of carambola fruit ßy females that copulated with carambola fruit ßy males had sperm in their spermathecae. By comparison, 0% (0/6 ßies) were mated in the case of carambola fruit ßy  mated to oriental fruit ßy  when both oriental fruit ßy sexes were present, whereas 50% (2/4 ßies) were mated when males-only oriental fruit ßy were released. KEY WORDS Bactrocera, oriental fruit ßy, carambola fruit ßy, light intensity, hybridization, sterile insects A SPECIES OF Bactrocera fruit ßy was discovered in Suriname in 1975 (van Sauers-Muller 1991, Iwahashi et al. 1996). The most likely cause of introduction was through trade or tourism from Indonesia (van Sauers- Muller 1991). The ßy was typed as “near dorsalis” by Drew and Hancock (van Sauers-Muller 1991), or “dor- salis Malaysia A” (Drew 1991), and Þnally as Bactro- cera carambolae, the carambola fruit ßy, (Drew and Hancock 1994). The ßy spread rapidly along habitable coastline areas, from Suriname to neighboring coun- triesÑGuyana and French Guiana (van Sauers-Muller 1991), prompting its recognition as an economic prob- lem by the international community some 10 yr after its discovery. Because of the impending threat posed by the ßy, including the tangible imposition of quar- antines on food exports from the region, several na- tions and international agencies, under the general coordination of the International Fund for Agricul- tural Development (IFAD), have banded together to launch an aggressive campaign against B. carambolae in northern South America. The development of a male annihilation technique against the oriental fruit ßy, B. dorsalis, based on a strong attraction of male ßies to methyl eugenol (Steiner and Lee 1955, Steiner et al. 1965, Koyama et al. 1984), has formed the basis of the campaign against B. carambolae centered in Suriname (van Sauers-Mul- ler 1991, Iwahashi et al. 1996). Despite the successes of male annihilation programs in the Marianas (Steiner et al. 1970), Japan (Koyama et al. 1984), and repeatedly in California (USA) (Chambers 1977), the technique failed to eradicate oriental fruit ßy in the Ogasawara Islands of Japan (Christenson 1963), pos- sibly because of the presence of males that did not 1 Tropical Fruit, Vegetable and Ornamental Crop Research Labo- ratory, USDA-ARS, Honolulu, HI. 2 Methods Development Station, USDA/APHIS/PPQ, Guatemala City, Guatemala. 3 Tropical Fruit, Vegetable and Ornamental Crop Research Labo- ratory, USDA-ARS, Hilo, HI. 4 Suriname Ministry of Agriculture, Animal Husbandry and Fish- eries, Carambola Fruit Fly Project, Paramaribo, Suriname. 5 Instituto de Biociencias, Universidade de Sao Paulo, Sao Paulo, Brazil. 6 IICA, Carambola Fruit Fly Project, Paramaribo, Suriname. Downloaded from https://academic.oup.com/aesa/article/92/5/758/97321 by guest on 25 January 2023