In Veracruz State, Mexico, the temporal and spatial distributions of 5 species of parasitic Hymenoptera attacking larvae of 5 Anastrepha species in 7 species of fruit tree canopies were examined. Parasitism by Doryctobracon areolatus (Szepligeti) (Braconidae), Diachasmimorpha longicaudata (Ashmead) (Braconidae), and Utetes anastrephae (Viereck) (Braconidae) was higher in 3 of 4 significant cases in the lower portions of the canopies. U. anastrephae was more abundant in the interior of canopies (2 cases), whereas D. areolatus was more common in the margins (1 case). In 6 of 7 instances the mean sizes of fruits containing parasitoids were smaller than those of infested fruits without parasitoids. U. anastrephae attacked larvae in a narrow range of smaller host-fruit species relative to other parasitoids. The efficiency (proportion of larvae attacked in a fruit) of D. longicaudata compared to that of other parasitoids increased with fruit size. D. longicaudata may be better able to locate or attack hosts in larger fruits. In all of 17 instances there were on average more host larvae in fruits containing parasitoids than in fruits without parasitoids. In all of 18 significant instances the larval density (larvae per gram weight of fruit) was higher in fruits that contained parasitoids than in fruits that did not. Parasitism by D. areolatus, Doryctobracon crawfordi (Viereck), D. longicaudata, and U. anastrephae often changed over time during the fruiting period, but was as likely to decrease as increase. D. areolatus had a pattern of decreasing parasitism during the fruiting periods of individual trees as the season changed from rainy to dry. There were only a few instances of significant relationships between parasitism and local differences in the canopy with respect to fruit numbers, host numbers, and host density. In 2 instances there were significant negative relationships between parasitism caused by the commonly cooccurring D. areolatus and U. anastrephae. In 2 other cases, parasitism by D. crawfordi and D. longicaudata was positively correlated. D. longicaudata is a recent introduction to Mexico and the positive relationships may indicate a niche overlap not present between the 2 native species, D. areolatus and U. anastrephae. Fewer than expected numbers of fruits containing both D. areolatus and U. anastrephae together was further evidence of niche differences. This pattern did not occur in fruits containing D. crawfordi and D. longicaudata. Information on the distribution of parasitoids at levels ranging from within canopies to across regions may guide biological control efforts, allowing the match of candidate species to locations.

We report the results of a 2-yr survey that determined some of the host plant and parasitoid associations of Anastrepha fruit flies (Diptera: Tephrit

We provide ecological evidence for the existence of diapause in 4 native and an exotic species of larval–pupal fruit fly (Diptera: Tephritidae) parasitoids inhabiting tropical environments. We worked in central Veracruz, Mexico, in perturbed tropical deciduous and subdeciduous forests and in diversified agroecosystems during 4 yr (1993–1997). The native parasitoid species Doryctobracon areolatus (Szépligeti), Utetes (B.) anastrephae (Viereck) (Hymenoptera: Braconidae), Aganaspispellenaroi (Brethes), dontosemaanastrephae Borgmeier (Hymenoptera: Eucoilidae), and the introduced species, Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae) all exhibited diapause. Importantly, none of the 6 Ancistrepha species serving as hosts for these parasitoids entered diapause. The larval-pupal parasitoids Doryctobracon crawfordi (Viereck) (Hymenoptera: Braconidae; native) and Aceratoneuromyia indica (Silvestri) (Hymenoptera: Eulophidae; introduced) and the pupal parasitoids Coptera haywardi (Hymenoptera: Diapriidae; native), and Pachycrepoideus vindemiae (Rondani) (Hymenoptera: Pteromalidae; introduced) did not exhibit diapause even though they were collected in the same region and at the same time of year. Importantly, in diapausing species not all populations exhibited the phenomenon and, furthermore, in those that did, patterns were polymodal (proportion of a given population entering diapause fluctuated between 0.4 and 100% depending on species). All diapausing individuals dissected from fly pupae were 3rd instars. Diapause lasted up to 11 mo (depending on the particular species) and was predominantly observed in fly pupae collected between the months of September and December (time of year when temperature and rainfall drops and days become shorter). Based on observations on tree fruiting phenology, we conclude that diapause is an effective mechanism allowing parasitoids to bridge periods during which fruit fly hosts (i.e., larvae) are scarce or not available. We discuss our findings in light of their ecological and practical implications.