Oviposition Responses of Female Mediterranean Fruit Flies (Diptera: Tephritidae) to Fruit Volatile Compounds

The Mediterranean fruit fly, Ceratitis capitata (Wiedemann), is one of the most important pests of fruits worldwide. In the present study, we investigated the ovipositional response of C. capitata females to 37 compounds of fruit volatiles from various chemical groups and the dose response to five of them. Red plastic hollow hemispheres (domes) were used as oviposition substrates in all tests. Twenty of the compounds tested increased female egg laying compared to control substrates that contain no chemicals. With 16 compounds, similar number of eggs was deposited in treated and in control oviposition substrates. One terpene ((±)-linalool) reduced egg laying indicating a deterrent ovipositional effect. Both the esters and aldehydes tested increased the ovipositional responses in C. capitata. Most of the monoterpene hydrocarbons increased oviposition, while oxygenated monoterpenes, sesquiterpenes hydrocarbons, and oxygenated sesquiterpenes had mostly neutral effect. Ethyl hexanoate and R-(+)-limonene increased oviposition in the majority of doses tested. Different doses of (−)-linalool elicited differential female ovipositional responses. In contrast, valencene and citral, regardless of dose did not affect female oviposition. Practical implications of these findings are discussed.

Influence of Substrate Age on Oviposition Behavior of a Specialist Carrion Colonizer, Cochliomyia macellaria (Diptera: Calliphoridae)

The location and consumption of carrion by arthropods is a process that can be potentially distinguished temporally based on the makeup of the associated community. In fact, succession on carrion is a continuum of different generalist and specialist arthropods entering and leaving the system. Blow flies commonly associated with vertebrate remains are considered specialists due to their reliance on carrion as a source of food for offspring and protein for females. However, this specialization may come at a price; increased competition for resources and greater risk of local extinction. The present study examined the effects of the presence or absence of intraspecific colonization, carcass age, and exposure time on the colonization and oviposition responses of the specialist, primary colonizer, the secondary screw worm, Cochliomyia macellaria (Fabricius) (Diptera: Calliphoridae). Carcass age, exposure time, and colonization status significantly influenced the ovipositional response of C. macellaria. This species exhibited an oviposition preference for aged carcasses, with a tendency for higher oviposition after 8-h exposure time, but no preference between previously colonized or uncolonized carcasses. Mean egg hatch rate was also shown to be influenced by the aforementioned factors, with mean hatch rates varying between 81.26 and 90.97% across various treatments. These results provide insight into mechanisms driving succession on carrion, as well as highlight the variation observed in successional studies for the targeted species. Investigators relying on arthropod succession to indicate a time of colonization should proceed with caution in relying solely on the assumption primary colonizers only arrive and colonize fresh carrion.

Suitability and Feeding Preference of Selected North American, European, and Asian Elm (Ulmus spp.) Biotypes to Elm Leaf Beetle (Coleoptera: Chrysomelidae)

Recently introduced North American elm cultivars, simple and complex elm hybrids of European and Asian parentage, and simple Asian hybrids of U. pumila and U. japonica parentage growing at The Morton Arboretum, Lisle, IL, were evaluated in laboratory bioassays for ovipositional response, and feeding preference and suitability for larvae and adults of the elm leaf beetle, Xanthogaleruca luteola (Muller). Larval and adult no-choice and adult multiple-choice feeding studies revealed that the North American cultivars of U. americana ‘Jefferson’ and U. americana ‘Valley Forge’, U. americana (diploid form), and U. americana were the least preferred for feeding and reproduction by the elm leaf beetle. Among simple and complex European hybrids, ‘Homestead’, ‘Patriot’, and ‘Prospector’ were least preferred and least suitable for larval development, feeding, and reproduction by adult elm leaf beetles. Hybrids of ‘Frontier’, ‘Pioneer’, and ‘Regal’; the simple Asian hybrids of ‘Cathedral’ and ‘New Horizon’; and U. pumila were more highly preferred for feeding and suitable for reproduction. The least preferred and least suitable North American biotypes of U. x americana ‘Jefferson’, U. americana ‘Valley Forge’, and U. americana (diploid form), simple and complex European hybrids of ‘Homestead’, ‘Patriot’, and ‘Prospector’, show promise for use in areas where the elm leaf beetle is persistent and for future elm breeding programs.

Ovipositional Stimuli of Angoumois Grain Moth (Lepidoptera: Gelechiidae), a Primary Pest of Stored Grains

Ovipositional preferences of Sitotroga cerealella (Olivier) were measured in the laboratory to characterize the stimuli eliciting oviposition in this widespread pest of stored grains. Substrates used for oviposition included grains presenting both physical and chemical stimuli as well as surrogates presenting only physical stimuli. Chemical factors associated with grains stimulated oviposition, but physical stimuli, primarily the presence of crevices, were of much greater importance. Moths reared for approximately 15 generations in the laboratory were less sensitive to grain factors than were moths more recently collected from the field. Experiments with surrogrates presenting a precisely defined range of crevice sizes confirmed that ovipositional response increased as crevice size narrowed. The results suggest that factors influencing habitat selection are probably very important in this insect because of indiscriminate oviposition on substrates that present appropriate physical stimuli but are entirely unsuitable for larval consumption.

Attractancy and Ovipositional Response of Adult Bemisia argentifolii (Homoptera: Aleyrodidae) to Type IV Trichome Density on Leaves of Lycopersicon hirsutum Grown in Three Day-Length Regimes

Clonal plants of six accessions of Lycopersicon hirsutum Humb. and Bonpl., a wild relative of tomato, were grown in three day-length regimes. Clones of an accession grown in different day-length regimes were genetically identical but differed in density of type IV and type VI trichomes on their leaves. Leaves on these plants were then evaluated for resistance to whiteflies (Bemisia argentifolii Bellows and Perring) in choice and non-choice bioassays. Plants grown under short days had elevated type IV density, reduced type VI trichome density, and were less attractive to whiteflies. Correlation and covariance analysis supported the hypothesis that high type IV trichome density resulted in reduced attractancy, especially on plants grown under short days.