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Deceptive flowers decoy pollinators by advertising a reward, which finally is not provided. Numerous deceptive plants are pollinated by Diptera, but the attractive cues and deceptive strategies are only identified in a few cases. A typical fly-deceptive plant genus is Aristolochia, which evolved sophisticated trap flowers to temporarily capture pollinators. Though rarely demonstrated by experimental approaches, Aristolochia species are believed to chemically mimic brood sites, food sources for adult flies, or utilize sexual deception. Indeed, for most species, studies on scent composition and attractive signals are lacking. In this study, we focused on Aristolochia microstoma, a peculiar Greek endemic with flowers that are presented at ground level in the leaf litter or between rocks and are characterized by a unique morphology. We analyzed flower visitor and pollinator spectra and identified the floral scent composition using dynamic headspace and gas chromatography coupled to mass spectrometry (GC/MS). Female and male phorid flies (Phoridae) are the exclusive pollinators, although the flowers are also frequently visited by Sciaridae, as well as typical ground-dwelling arthropods, such as Collembola and arachnids. The carrion-like floral scent mainly consists of the oligosulphide dimethyldisulfide and the nitrogen-bearing compound 2,5-dimethylpyrazine. These compounds together are known to be released from decomposing insects, and thus, we conclude that pollinators are likely deceived by chemical imitation of invertebrate carrion, a deceptive strategy not described from another plant species so far.

The oviposition behavior of mosquitoes is mediated by chemical cues. In the malaria mosquito Anopheles gambiae, conspecific larvae produce infochemicals that affect this behavior. Emanations from first instar larvae proved strongly attractive to gravid females, while those from fourth instars caused oviposition deterrence, suggesting that larval developmental stage affected the oviposition choice of the female mosquito. We examined the nature of these chemicals by headspace collection of emanations of water in which larvae of different stages were developing. Four chemicals with putative effects on oviposition behavior were identified: dimethyldisulfide (DMDS) and dimethyltrisulfide (DMTS) were identified in emanations from water containing fourth instars; nonane and 2,4-pentanedione (2,4-PD) were identified in emanations from water containing both first and fourth instars. Dual-choice oviposition studies with these compounds were done in the laboratory and in semi-field experiments in Tanzania. In the laboratory, DMDS and DMTS were associated with oviposition-deterrent effects, while results with nonane and 2,4-PD were inconclusive. In further studies DMDS and DMTS evoked egg retention, while with nonane and 2,4-PD 88% and 100% of female mosquitoes, respectively, laid eggs. In dual-choice semi-field trials DMDS and DMTS caused oviposition deterrence, while nonane and 2,4-PD evoked attraction, inducing females to lay more eggs in bowls containing these compounds compared to the controls. We conclude that oviposition of An. gambiae is mediated by these four infochemicals associated with conspecific larvae, eliciting either attraction or deterrence. High levels of egg retention occurred when females were exposed to chemicals associated with fourth instar larvae. Electronic supplementary material The online version of this article (10.1007/s10886-020-01175-5) contains supplementary material, which is available to authorized users.

Our understanding of the role of cuticular hydrocarbons (CHC) in recognition is based largely on temperate ant species and honey bees. The stingless bees remain relatively poorly studied, despite being the largest group of eusocial bees, comprising more than 400 species in some 60 genera. The Meliponini and Apini diverged between 80–130 Myr B.P. so the evolutionary trajectories that shaped the chemical communication systems in ants, honeybees and stingless bees may be very different. The aim of this study was to study if a unique species CHC signal existed in Neotropical stingless bees, as has been shown for many temperate species, and what compounds are involved. This was achieved by collecting CHC data from 24 colonies belonging to six species of Melipona from North-Eastern Brazil and comparing the results with previously published CHC studies on Melipona. We found that each of the eleven Melipona species studied so far each produced a unique species CHC signal based around their alkene isomer production. A remarkable number of alkene isomers, up to 25 in M. asilvai, indicated the diversification of alkene positional isomers among the stingless bees. The only other group to have really diversified in alkene isomer production are the primitively eusocial Bumblebees (Bombus spp), which are the sister group of the stingless bees. Furthermore, among the eleven Neotropical Melipona species we could detect no effect of the environment on the proportion of alkane production as has been suggested for some other species. Electronic supplementary material The online version of this article (10.1007/s10886-017-0901-5) contains supplementary material, which is available to authorized users.

In the present research, an industrially aged Pt/Al 2 O 3 catalyst was used as a basis for the study on the sulfur deactivation and the development of more resistant catalytic materials. The catalytic activities of both industrially and laboratory-aged materials in DMDS oxidation were studied in addition to characterization by XRD, XPS, FESEM, TEM and N 2 adsorption. The industrial ageing induced a phase change from γ-Al 2 O 3 towards θ-Al 2 O 3 , formation of aluminum sulfates and an increase in Pt particle size as well as a change in the oxidation state of Pt to a higher state. These changes caused an increase of 30 °C in the light-off temperature for DMDS oxidation. Accelerated ageing in the presence of SO 2 and H 2 O vapor at 400 °C for 5 h decreased the activity of the Pt/Al 2 O 3 at the same level than for the industrially aged catalyst even though smaller sulfur content and no sintering of γ-Al 2 O 3 were observed. Pt sintering (10–20 nm) in both cases was observed. The XPS results confirmed the formation of new sulfate phases and the interaction between sulfur and the active phase as well as the support of the catalyst undergone accelerated ageing. After the accelerated ageing of copper-based catalysts, the 0.3Pt10Cu/Al 2 O 3 ǀ 0.8 SiO 2 ǀ 0.2 catalyst showed an interesting resistance towards sulfur deactivation, as it was expected.

The work in this thesis concentrates on finding more active and durable catalysts for the demanding environmental application of the oxidation of sulfur-containing volatile organic compounds (S-VOCs). This application is challenging due to the high purification levels required and the catalyst deactivating nature of sulfur. In this thesis, dimethyldisulfide (DMDS) was used as the model molecule to represent S-VOCs since it is often present in odorous emissions and it is more difficult to treat than most of the other S-VOCs. It was found that the addition of a very small amount of Pt (0.3%) especially improves the selectivity of copper oxide based catalysts towards complete oxidation products ((carbon dioixide (CO2), water (H2O) and sulfur dioxide (SO2)) in DMDS oxidation. Catalyst characterization by transmission electron microscopy, temperature programmed reduction and X-ray photoelectron spectroscopy analyses suggests that this promoting effect is most likely due to the close interaction between Cu and Pt species on the bimetallic PtCu/γ-Al2O3 catalyst. The drawback of using the Al2O3 support is that it is not resistant towards sulfur poisoning. The deactivation of the self-made catalysts was studied with the help of an accelerated ageing procedure that was developed based on the information from the industrially aged volatile organic compound (VOC) catalysts. Industrial deactivation was caused by the sintering of the support and active metals and by the formation of metal sulfates with the support. After accelerated ageing, the silica doped alumina (Al2O3)0.8(SiO2)0.2 supported catalyst, showed remarkably promising results in terms of stability towards sulfur poisoning and the activity in DMDS oxidation was very close to that of the most active PtCu/Al2O3. The addition of less than 20% of SiO2 on the Al2O3 support led to a catalyst that is more selective and resistant to sulfur poisoning. Tiivistelmä Väitöskirjassa tuotetaan uutta tietoa rikkipitoisten orgaanisten yhdisteiden (S-VOC) hapetukseen soveltuvien uusien katalyyttisten materiaalien synteesistä ja karakterisoinnista. S-VOC-yhdisteiden käsittely on vaativa katalyyttisen polton sovellus, koska näiden päästöjen käsittely edellyttää korkeaa puhdistustehoa, ja lisäksi yhdisteiden sisältämä rikki on katalyyttimyrkky. Tässä väitöskirjassa valittiin S-VOC-yhdisteitä edustavaksi malliaineeksi dimetyylisulfidi (DMDS), koska se on usein mukana käsiteltävissä S-VOC-päästöissä ja sen käsittely on vaativampaa kuin useiden muiden S-VOC-yhdisteiden käsittely. Tutkimustulosten mukaan hyvin pieni Pt-lisäys (0.3 %) parantaa erityisesti kuparioksidikatalyyttien selektiivisyyttä DMDS:n kokonaishapetustuotteiksi (CO2, H2O, SO2). Katalyyttien karakterisoinnin (läpäisyelektronimikroskopia, lämpötilaohjattu pelkistysreaktio, röntgensädefotoelektronispektroskopia) perusteella voidaan esittää parannuksen syyksi kuparin ja platinan läheinen kontakti bimetallisen PtCu/γ-Al2O3-katalyytin pinnalla. Al2O3-tukiaineen heikkoutena on sen deaktivoitumisherkkyys rikkiyhdisteiden läsnä ollessa. Väitöskirjatyössä valmistettujen katalyyttien deaktivitumista tutkittiin laboratoriomittakaavassa nopeutettujen ikäytyskokeiden avulla, jotka kehitettiin teollisessa käytössä deaktivoituneen katalyytin karakterisointien avulla saadun tiedon perusteella. Teollisessa käytössä olleen katalyytin deaktivoitumisen syyksi havaittiin tukiaineen ja aktiivisten metallien sintrautuminen sekä metallisulfidien muodostuminen tukiaineen kanssa. Nopeutettujen ikäytyskokeiden tulosten perusteella havaittiin, että piidioksidin lisäys alumiinioksiditukiaineeseen paransi tukiaineen rikin kestoa merkittävästi. Tutkimuksissa havaittiin myös, että piidioksidilla muokatun katalyytin aktiivisuus oli hyvin lähellä vastaavaa PtCu/γ-Al2O3-katalyytin aktiivisuutta. DMDS:n hapetuksessa selektiivisempi ja stabiilimpi katalyytti voidaan aikaansaada alle 20 %:n SiO2-lisäyksellä Al2O3-tukiaineeseen.

International audience; Due to their harmful effects, finding the optimal catalysts for Sulfur containing Volatile Organic Compounds (S-VOC) oxidation is an important environmental challenge. A series of Pt-Cu catalysts supported on alumina (Al2O3), silica (SiO2) and silica doped alumina (Al2O3)(0.8)(SiO2)(0.2) were prepared and tested in the catalytic oxidation of dimethyldisulfide (DMDS). Characterization of the catalysts revealed that the performance of the catalyst is related to the interaction between Pt-Cu active phase and the supports. DMDS conversion on the Pt-Cu/Al2O3 catalyst was found to be close to that of the Pt-Cu/(Al2O3)(0.8)(SiO2)(0.2) catalyst. However, doping the Al2O3 substrate by SiO2 led to a more selective and stable catalyst.