Host use and resource sharing by fruit/seed-infesting insects on Schoepfia schreberi (Olacaceae)

Insights into the Interaction between the Monophagous Tephritid Fly Anastrepha acris and its Highly Toxic Host Hippomane mancinella (Euphorbiaceae)

Despite their enormous economic importance and the fact that there are almost 5000 tephritid (Diptera) species, fruit fly - host plant interactions are poorly understood from a chemical perspective. We analyzed the interactions among Anastrepha acris (a little studied monophagous tephritid) and its highly toxic host plant Hippomane mancinella from chemical, ecological and experimental perspectives, and also searched for toxicants from H. mancinella in the larval-pupal endoparasitoid Doryctobracon areolatus. We identified 18 phenolic compounds from H. mancinella pulp belonging to different chemical groups including phenylpropanoids, flavonoids, chalcones and coumarins. No traces of Hippomanin A were detected in larvae, pupae or A. acris adults, or in D. areolatus adults, implying that A. acris larvae can metabolize this toxicant, that as a result does not reach the third trophic level. We tested the "behavioral preference - lack of larval specialization-hypothesis" via feeding experiments with a larval rearing medium containing H. mancinella fruit (skin + pulp or pulp alone). The high toxicity of H. mancinella was confirmed as only two (out of 2520 in three experiments) A. ludens larvae (a polyphagous pest species that preferentially feeds on plants within the Rutaceae) survived without reaching the adult stage when fed on media containing H. mancinella, whereas A. acris larvae developed well and produced healthy adults. Together, these findings open a window of opportunity to study the detoxification mechanisms used by tephritid fruit flies.

Patterns of Oviposition and Feeding in the Monophagous Fly Anastrepha spatulata (Diptera: Tephritidae) on its Larval Host Plant Schoepfia schreberi

Monophagous insects that use discrete resources for oviposition and feeding are especially sensitive to variations in host quality and availability because their opportunities to find these resources are scarce. The monophagous tephritid fly Anastrepha spatulata Stone is a tephritid fly that uses as hosts the fruits of the non-economically important Schoepfia schreberi J. F. Gmel. Scant information of host utilization behavior in the field is available for this species. Wild individually marked flies were observed during the fruiting season. Observations of oviposition, feeding and resting on three trees were taken hourly from 0900 to 1800 hours on days with benign weather. Our results suggest that females can use fruits for oviposition or for feeding according to a temporal scale. Females were significantly more likely to feed on smaller hosts and oviposit in larger ones. Additionally, individual variation in host patch exploitation was detected. However, females that fed on a natural food source such as host fruit juice oviposited fewer eggs than females provided an artificial diet of sucrose and hydrolyzed yeast. Results indicate that females use different foraging tactics during the fruiting season and confirm that, in this case, the host plant is not the center of activity.

Natural enemy defense, provisioning and oviposition site selection as maternal strategies to enhance offspring survival in a sub-social bug

The influence of maternal defense against natural enemies, maternal provisioning and oviposition site selection on offspring survival before and after hatching were examined in a semelparous pentatomid bug, Ramosiana insignis. Oviposition occurs on leaves of Schoepfia schreberi, or surrounding vegetation from which nymphs migrate to feed exclusively on S. schreberi flower buds. Oviposition is asynchronous; the mother lays additional eggs immediately prior to hatching of the core brood that rapidly consume the additional eggs. In the absence of maternal defense egg masses were more heavily parasitized, suffered ant predation and an increased prevalence of sibling cannibalism. Maternal provisioning in the form of addition eggs significantly reduced the prevalence of sibling cannibalism of core brood eggs. Migration of the core brood away from the oviposition site was also significantly higher in the absence of maternal provisioning. If not consumed, additional eggs were capable of producing viable progeny of both sexes, indicating that they were in fact marginal progeny. The average clutch size on non-host vegetation was numerically greater than clutches laid on host trees (borderline significant P = 0.058). A greater number of additional eggs were deposited with clutches laid on non-host vegetation compared to those on the host plant. Egg masses on non-host vegetation were less likely to be discovered by parasitoids, compared to those on the host tree. Overall, clutches on non-host vegetation produced one third more offspring than clutches on the host tree. We conclude that R. insignis females present a remarkable combination of maternal defense, provisioning of additional eggs and oviposition site selection as strategies to enhance offspring survival in both the egg and nymph stages.