The relationships between Anastrepha species and their host plants are recorded and analyzed from a study carried out in a natural tropical community of Mexico (Estacion de Biologia Tropical Los Tuxtlas, Veracruz). We sampled fruits of 55 plant species of the tropical rain forest and found the following associations: Tapirira mexicana Marchand was infested with A. sp. and A. obliqua (Macquart)
Spondias radlkoferi J. D. Smith with A. obliqua
Tabernaemontana alba Mill. with A. cordata Aldrich
Quararibea funebris (Llave) Vischer with A. crebra Stone
Inga sapindoides Willd. with A. distincta Greene
Brosimum alicastrum Sw. and Pseudolmedia oxyphyllaria J. D. Smith with A. bahiensis Costa Lima
Psidium guajava L. with A. striata Schiner and A. fraterculus (Wiedemann)
Citrus aurantium L. and C. maxima (Burm.) Merrill with A. ludens (Loew)
Chrysophyllum mexicanum Brandegee ex Standley, Pouteria sapota (Jacq.) H. Moore & Stearn and Pouteria sp. with A. serpentina (Wiedemann). Also, we found the species A. hamata (Loew), A. leptozona Hendel and A. minuta Stone, whose hosts in the Los Tuxtlas region are still unknown. We sampled infestation rates in 10 of the 13 host plants. Of the 3704 fruits examined, 23.1% were infested. We encountered 2290 larvae, of which 1600 pupated. Parasitoids or adult flies emerged from 85% of these. Infestation percentages of the different fruit species were highly variable, ranging from 1. 5% for P. oxyphyllaria to 66.7% for Pouteria sapota. The mean number of larvae per fruit usually was between 1.25 and 2.59, and in only the largest and heaviest fruits (such as C. aurantium, P. sapota and P. sp.) were there more than 9.0 larvae present. Some fruit characteristics affecting the degree of infestation are discussed, and the possible existence of a diapause period in some Anastrepha species is noted.