Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/6/2005
Publication Date: 12/10/2005
Citation: Aluja, M., Sivinski, J.M., Rull, J., Hodgson, P.J. 2005. Behaviour and predation of fruit fly larvae (Anastrepha spp.) (Diptera: Tephritidae) after exiting fruit in four types of habitats in tropical Veracruz, Mexico. Environmental Entomology. 34(6):1507-1516. Interpretive Summary: Tephritid fruit flies are destroy scores of fruits and vegetables and are responsible for export barriers wherever they occur. There would be serious economic consequences should Mexican species invade the USA, and information on the insects that consume them in their native habitat might lead to lessening the danger of their importation into the USA or helping prevent establishment if they were imported. Scientists at the USDA-ARS Center for Medical, Agricultural and Veterinary Entomology (Gainesville, Florida) in collaboration with Colleagues at the Instituto de Ecologia (Xalapa, Veracruz, Mexico) studied the effect of predatory ants on fruit fly larvae after they leave fruit and seek to pupate in the ground. It was discovered that environmental factors influenced the proportions of larvae that were consumed and that some of these factors can be manipulated to increase fly mortality. Further studies seeking to conserve natural enemies, such as ants, and to amplify their effect are underway.
Technical Abstract: We report results of field observations and experiments describing larval behaviour and identifying biotic and abiotic mortality factors from the moment mature frugivorous tephritid larvae leave fruit until they secure pupation sites in the soil. Observations and experiments were performed in four different environments at three localities in the state of Veracruz, México that differed in climate, soil structure, and host plant composition (trees of Spondias purpurea [tropical plum or 'ciruela'], Spondias mombin [tropical plum or 'jobo'], Psidium guajava (guava), and Citrus sinensis (orange) in located in Apazapan, Llano Grande, and Tejería [guava and orange], respectively). Pupal distribution was influenced only by fruit position, while shade, litter depth, average soil temperature, soil pH, vegetation cover, and number of predacious insects per surface unit did not contribute in explaining variance in pupal distribution. At all sites, most larvae (90%) entered the soil within ten minutes and ants commonly attacked larvae within 5 minutes of exit from fruit at all but one site (Tejeria ' Orange). Only at one site, Apazapan, did larvae die due to climatic exposure during the hottest part of the day. The most important mortality factor at all sites was predation by ants, which in turn was influenced by temperature, humidity, and soil dampness, and varied significantly among host treeS within a site. At all sites, close to 60% of larvae were subsequently recovered as pupae in the soil after sieving. No consistent relationship was observed between distance moved away from fruit and depth of pupation WITHIN sites. Most larvae exited guavas (P. guajava) during the early cool part of the day (4:00 to 8:00 a.m.), while larvae left oranges across a wider time span with 60% of exits occurring between 4:00 a.m and 12:00 p.m. Except for S. purpurea, where most larvae exited beneath fruit, exit holes were evenly distributed in oranges, guavas, and S. mombin. In laboratory experiments, larvae exposed to ant attack pupateD at greater depths than larvae exposed to ants but not attacked which in turn pupateD at greater depths than larvae not exposed to ants. We discuss the importance of predation in shaping tephritid larval behavior and implications of the effects of environmental factors on predation for biological control programs using conservation of natural enemies as a tool.