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Siren molecule calls loudly to mosquitoes People infected by malaria become more attractive to the mosquito vectors of the disease, which facilitates the spread of malaria. Emami et al. found that red blood cells of the host respond to a parasite-derived isoprenoid called HMBPP by increasing the production of carbon dioxide and several monoterpenes and aldehydes. Mosquitoes fed HMBPP-spiked blood displayed malaria parasite–specific changes in gene transcription, which reinforced attractiveness for the mosquito. HMBPP also stimulates mosquito feeding and malaria parasite reproduction. Thus, the parasite manipulates its mammalian host to make it more attractive to the insect vectors and exploits the same molecule to amplify transmission. Science , this issue p. 1076

The male butterfly Pieris napi produces the anti-aphrodisiac pheromone methyl salicylate (MeS) and transfers it to the female during mating. After mating she releases MeS, when courted by conspecific males, which decreases her attractiveness and the duration of male harassment, thus increasing her time available for egg-laying. In previous studies we have shown that males produced MeS from the amino acid L-phenylalanine (L-Phe) acquired during larval stage. In this study we show that adult males of P. napi can utilize L-Phe and aromatic flower volatiles as building blocks for production of anti-aphrodisiac pheromone and transfer it to females during mating. We demonstrate this by feeding butterflies with stable isotope labelled molecules mixed in sugar solutions, and, to mimic the natural conditions, we fed male butterflies with floral nectar of Bunias orientalis plants treated with labelled L-Phe. The volatiles from butterflies and plants were collected and identified by solid phase micro extraction, gas chromatography and mass spectrometry techniques. Since P. napi is polygamous, males would gain from restoring the titre of MeS after mating and the use of aromatic precursors for production of MeS could be considered as an advantageous trait which could enable butterflies to relocate L-Phe for other needs.

The cabbage moth, Mamestra brassicae L. (Lepidoptera, Noctuidae), is a polyphagous species that is often choosing plants of Brassica as hosts for oviposition. In the search for biologically relevant odorants used by these moths, gas chromatography linked to electrophysiological recordings from single receptor neurons (RNs) has been employed, resulting in classification of distinct types of neurons. This study presents specific olfactory RNs responding to methyl salicylate (MeS) as primary odorant and showing a weak response to methyl benzoate, the 2 aromatic compounds occurring together in several plant species. In 2 cases, the neuron was colocated with another RN type responding to 6 green leaf volatiles: 1-hexanol, (3Z)-hexen-1-ol, (2E)-hexen-1-ol, (3Z)-hexenyl acetate, (2Z)-hexen-1-ol, and an unidentified compound. Whereas the specific RNs detected the minor amounts of MeS in some plants, the compound was not found by gas chromatography linked to mass spectrometry in intact plants, but it was found after herbivore attack. The behavioral effect of MeS was studied in outdoor test arenas with Brassica napus and artificial plants. These experiments indicated that mated M. brassicae females avoid plants with dispensers emitting MeS. As it is induced by caterpillar feeding, this compound may mediate a message to mated M. brassicae females that the plant is already occupied.

A chemical analysis of the crude sex pheromone gland extracts of virgin calling Paranthrene tabaniformis females, obtained from the European part of Kazakhstan, revealed the presence of five compounds: (3E,13Z)-octadeca-3,13-dien-1-ol (E3,Z13-18:OH), (3Z,13Z)- octadeca-3,13-dien-1-ol (Z3,Z13-18:OH), (2E,13Z)-octadeca-2,13-dien-1-ol (E2,Z13-18:OH), (13Z)-octadec-13-en-1-ol (Z13-18:OH), and octadecan-1-ol (18:OH) at the ratios 64.0 : 32.4 : 1.4 : 0.9 :1.3, which are structurally related to sex pheromone components of clearwing moths. Our previous field tests showed synergistic effects of Z3,Z13-18:OH and E2,Z13-18:OH to attract P. tabaniformis males, when these compounds were tested in binary mixtures with the known sex pheromone E3,Z13-18:OH. The three dienic alcohols should all be considered as sex pheromone components of the P. tabaniformis species, while the role of Z13-18:OH and 18:OH remained unclear.

Sex attractants were established for one Brachodidae, three Choreutidae and two Tineidae moth species during field screening tests with (2E,13Z)-octadecadien-1-al, (2E,13Z)-, (3E,13Z)-, (3Z,13Z)-octadecadien-1-ols and their acetates (2E,13Z-18:Ald, 2E,13Z-, 3E,13Z-, 3Z,13Z-18:OH/OAc) as well as of binary mixtures of these compounds in West-Kazakhstan and Lithuania. Males of Brachodes appendiculata were attracted by 3E,13Z-18:OAc, Prochoreutis ultimana and P. myllerana by 2E,13Z-18:OH, Monopis palidella by 2E,13Z-18:Ald and Triaxomera fulvimitrella by binary mixtures of 3Z,13Z-18:OAc with either 3E,13Z-18:OH in the ratio of 5:5 or 3Z,13Z-18:OH in the ratio of 9:1 (v/v). The 3-component mixture composed of 2E,13Z-18:OH, 3Z,13Z-18:OH and 2E,13Z-18:Ald in the ratio 1:1:1 was developed to attract Prochoreutis sehestediana males. Attraction antagonists for B. appendiculata, P. ultimana and M. palidella were shown.

Sex attractants for 3 Sesiidae and 3 Tineidae moth species in West-Kazakhstan and Lithua­nia were discovered by field screening tests of (3Z,13Z)-, (3E,13Z)-and (2E,13Z)-octadeca-dien-1-ols and their acetates as well as of some binary mixtures of these compounds. Total amount of chemicals was 0.3 mg/dispenser. Males of Synanthedon serica were attracted by a 5:5 mixture of 3E,13Z-18:OA c and 2E,13Z-18:OAc, Chamaesphecia bibioniformis by a 9:1 mixture of 3Z,13Z-18:OAc and 3E,13Z-18:OAc, Paranthrene tabaniformis by a 1:9 mixture of 3Z,13Z-18:OH and 3E,13Z-18:OH , Tinea nonimella by a 1:9 mixture of 3E,13Z-18:OH and 2E,13Z-18:OH , Monopis monachella by a 1:9 mixture of 3Z,13Z-18:OH and 2E,13Z -18:OH, and Nemaxera betulinella by a 9:1 mixture of 2E,13Z-18:OAc and the corresponding alcohol. The periods of attraction to the traps were registered for males of S. serica and Ch. bibioniformis and were found to occur at 15 - 18 and 1 5 -17 o'clock, local time, respectively.

International audience; The enormous burden placed on populations worldwide by mosquito-borne diseases, most notably malaria and dengue, is currently being tackled by the use of insecticides sprayed in residences or applied to bednets, and in the case of dengue vectors through reduction of larval breeding sites or larviciding with insecticides thereof. However, these methods are under threat from, amongst other issues, the development of insecticide resistance and the practical difficulty of maintaining long-term community-wide efforts. The sterile insect technique (SIT), whose success hinges on having a good understanding of the biology and behaviour of the male mosquito, is an additional weapon in the limited arsenal against mosquito vectors. The successful production and release of sterile males, which is the mechanism of population suppression by SIT, relies on the release of mass-reared sterile males able to confer sterility in the target population by mating with wild females. A five year Joint FAO/IAEA Coordinated Research Project brought together researchers from around the world to investigate the pre-mating conditions of male mosquitoes (physiology and behaviour, resource acquisition and allocation, and dispersal), the mosquito mating systems and the contribution of molecular or chemical approaches to the understanding of male mosquito mating behaviour. A summary of the existing knowledge and the main novel findings of this group is reviewed here, and further presented in the reviews and research articles that form this Acta Tropica special issue.

Butterflies are believed to use mainly visual cues when searching for food and oviposition sites despite that their olfactory system is morphologically similar to their nocturnal relatives, the moths. The olfactory ability in butterflies has, however, not been thoroughly investigated. Therefore, we performed the first study of odour representation in the primary olfactory centre, the antennal lobes, of butterflies. Host plant range is highly variable within the butterfly family Nymphalidae, with extreme specialists and wide generalists found even among closely related species. Here we measured odour evoked Ca(2+) activity in the antennal lobes of two nymphalid species with diverging host plant preferences, the specialist Aglais urticae and the generalist Polygonia c-album. The butterflies responded with stimulus-specific combinations of activated glomeruli to single plant-related compounds and to extracts of host and non-host plants. In general, responses were similar between the species. However, the specialist A. urticae responded more specifically to its preferred host plant, stinging nettle, than P. c-album. In addition, we found a species-specific difference both in correlation between responses to two common green leaf volatiles and the sensitivity to these compounds. Our results indicate that these butterflies have the ability to detect and to discriminate between different plant-related odorants.

Two components of the female-produced sex pheromone of the hornet moth, Sesia apiformis, were identified as (3Z,13Z)-octadeca-3,13-dien-1-ol (3Z,13Z-18:OH) and (2E,13Z)-octadeca-2,13-dienal (2E,13Z-18:Al), a pheromone structure new in Sesiidae. Pooled gland extracts showed the two major compounds in a proportion of ca. 2:3, while SPME-investigations on single calling females revealed a ratio of ca. 1:7. Although the single compounds were not attractive, a 2:3 mixture proved to be highly active towards males in field tests. Small amounts of (2E,13Z)-octadecadienol (2E,13Z-18:OH) were found in the sex pheromone gland of females, however, the biological significance of the compound remains unclear. Methyl sulfide was found to readily react with 2-alkenals, providing an effective new method for the characterization of this type of compound upon GC/MS. The derivatives, 1,1,3-tris(methylthio)alkanes, are the products of the addition of methyl sulfide to the double bond and the transformation of the carbonyl group into the corresponding bis(methylthio)acetal. The mass spectra of these compounds are characterized by diagnostic signals at m/z 107 and/or m/z 121. These fragments represent the first carbon unit or the first two carbon units of the derivative, respectively. The parent signal in the spectra of thiomethyl derivatives of 2-alkenals showing no other double bonds is represented by m/z M+ – 121, formed upon loss of the first two carbon units. By employing a solution of methyl sulfide in dimethyl sulfide, the double bond positions in 2E,13Z-18:Al could be fully characterized by GC/MS.

The sesquiterpene germacrene D (GD) activates a major type of olfactory receptor neuron on the antennae of the heliothine moths. In Heliothis virescens females, 80% of the recordings have shown activity of one neuron type responding with high sensitivity and selectivity to GD. With the aim of determining the behavioural significance of this sesquiterpene, we have used a two-choice wind-tunnel to study the preference of mated H. virescens females for host plants with and without (-)-GD added. Tobacco plants containing dispensers with low release rate of (-)-GD had a greater attractiveness than tobacco plants without this substance. In addition, a significant increase of oviposition was found on the plants with (-)-GD.