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Rapid Collection of Floral Fragrance Volatiles using a Headspace Volatile Collection Technique for GC-MS Thermal Desorption Sampling

Fragrances of many flower families have been sampled and the volatiles analyzed. Knowing the compounds that make up the fragrances can be an important ...

Agricultural Research Service U.S. Department of Agriculture

While adult parasitic Hymenoptera in general feed on floral and extrafloral nectars, hemipteran-honeydews and fluids from punctured hosts, Diachasmimorpha longicaudata (Ashmead), an Old World opiine braconid introduced to tropical/subtropical America for the biological control of Anastrepha spp. (Tephritidae), can survive on fruit juices as they seep from injured fruit. An ability to exploit fruit juice would allow such a parasitoid to efficiently forage for hosts and food sources simultaneously. Two New World opiines, Doryctobracon areolatus (Szepligeti) and Utetes anastrephae (Viereck), are also prominent Anastrepha parasitoids and are roughly sympatric. All three species were provided with: (1) pulp and juice diets derived from a highly domesticated Old World fruit (orange, Citrus sinensis L.) that is only recently sympatric with the Mexican flies and parasitoids and so offered little opportunity for the evolution of feeding-adaptations and (2) a less-domesticated New World fruit (guava, Psidium guajava L.), sympatric over evolutionary time with D. areolatus and U. anastrephae. Both sexes of D. longicaudata died when provided guava pulp or juice at a rate similar to a water-only control. D. areolatus and U. anastrephae, presumably adapted to the nutrient/chemical constituents of guava, also died at a similar rate. Survival of all three species on orange pulp and juice was greater than on water, and often equaled that obtained on a honey and water solution. In confirmatory experiments in Mexico, D. areolatus and U. anastrephae, as well as other tephritid parasitoids Doryctobracon crawfordi (Viereck) and Opius hirtus (Fisher), all died at a significantly higher rates when provided guava in comparison to a honey and water diet. Such a result is likely due to guavas being repellent, innutritious or toxic. D. longicaudata clearly consumed guava juice tagged with a colored dye. Dilutions of orange and guava juice resulted in shorter lifespans than dilutions of orange juice and water demonstrating that there while diluted orange juice provided nutrition the addition of guava created toxicity. Given the differences in fruit-food quality, adult opiine food sources would not be obtainable at all oviposition sites and in the case of guava, more additional sites and foraging for food than previously postulated may be required.

Longevity of multiple species of tephritid (Diptera) fruit fly parasitoids (Hymenoptera: Braconidae: Opiinae) provided exotic and sympatric-fruit based diets.

South Florida is home to a number of native species of orchids. The Florida Panther National Wildlife Refuge has 27 known species, including Prosthechea cochleata, the clamshell orchid, which is listed as endangered on Florida's Regulated Plant Index. In a prior study done on this species in Mexico, P. cochleata was found to produce no floral fragrance at the particular study location. However, blooming orchids of this species at the University of Florida in Gainesville, were noted to be fragrant. In this paper, we document the presence of floral fragrance compounds from P. cochleata by using by gas chromatography mass spectrometry (GC/MS) analysis of headspace volatile collection. The orchids sampled were found to be consistently producing eight volatiles that are common in floral fragrances, including those of previous orchid species studied. By knowing the fragrance compounds produced, we can better understand the pollination biology of this endangered orchid. This information could be used to help future conservation efforts for P. cochelata by increasing pollination and subsequent seed capsule production.

Charles J. Stuhl

Center for Medical,
Agricultural and Veterinary Entomology,
Center for Medical, Agricultural and Veterinary Entomology

Agricultural Research Service U.S. Department of Agriculture

Rapid Collection of Floral Fragrance Volatiles using a Headspace Volatile Collection Technique for GC-MS Thermal Desorption Sampling

Charles J. Stuhl

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Agricultural Research Service U.S. Department of Agriculture

Rapid Collection of Floral Fragrance Volatiles using a Headspace Volatile Collection Technique for GC-MS Thermal Desorption Sampling

Center for Medical,
Agricultural and Veterinary Entomology,
Center for Medical, Agricultural and Veterinary Entomology