The external morphology and peripheral olfactory responses of antennal chemoreceptors of Trichogramma chilonis Ishii (Hymenoptera:Trichogrammatidae) to host related stimuli were examined by SEM and EAG technique respectively. The antennae of male and female T. chilonis reveal strong sexual dimorphism in structure as well as in types, density and distribution of individual sensillar types. The female antennae are characterized by the presence of a single uniporous sensilla on the apical tip of the dome and numerous multiporous pitted sensilla. Sensilla common to both males and females include the multiporous plate sensilla, the peg sensilla and trichoid sensilla. Differences between males and females occur with respect to their EAG profiles to 22 chemicals commonly found in plants viz.leaf extracts of three host plants of Helicoverpa armigera (cotton, chickpea and pigeon pea) and hexane scale extracts of adult males and females of H. armigera. Individually, the largest peak amplitudes in females were obtained with citronellal, phytol, caryophyllene, R-(+)-limonene, linalool, carvacrol and citronellol while in males citronellol, caryophyllene, linalool, R-(+)-limonene and amyl acetate caused the highest response. Among the different chemical classes, the largest peak amplitudes in females were obtained with oxygenated monoterpenes, while in males, fatty acid derivatives caused the highest response. In both males and females, the hydrocarbon monoterpenes caused the least response. Thus, the wide spectrum response of Trichogramma chilonis, to a wide group of chemicals belonging to different chemical classes, though varying, nevertheless suggests that using plant information enhances its parasitization efficiency.

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Sensilla on the maxillary and labial palpi of Leptinotarsa decemlineata were examined by scanning and transmission electron microscopy. There are a total of 370 sensilla on the apical tip of the maxillary palpi and 130 on the labial palpi. Four morphologically different types of sensilla are present on the maxillary palpi, three of which are common to the labial palpi. Type A sensilla, unique to the maxillary palpi, and type C sensilla have the structural characteristics of olfactory sensilla. Types B and D, with an apical pore, are considered contact chemoreceptors. Cuticular specializations, interrelationships of enveloping cells, comparative morphometry of dendrites, distribution of each sensillar type, and the predominance of olfactory sensilla are discussed in relation to feeding behavior.

Electroantennograms (EAGs)were recorded from males and females of the potato tuber moth,Phthorimaea operculella in response to a broad range of plant volatile compounds belonging to diverse chemical classes.The responses to 27 compounds were evaluated,which indicated significant differences in EAGs between chemicals as well as between sexes.The fatty acid derivatives comprising essentially green leaf volatile components elicited significantly greater responses in females.The response profile of males was,in general,lower than that of females.EAG responses to the oxygenated and hydrocarbon monoterpenes were lower in both males and females.Dose -response studies indicate differences in response between the sexes and concentrations,suggesting the existence of sexual dimorphism. Compounds belonging to the fatty acid derivatives class appear to be important for an oligophagous pest such as the potato tuber moth and the findings are discussed in relation to host plant selection in this species.

Here, we disclose novel mosquito-repellent synthetic hydrindanes based on noreremophilanes and nardoaristolone B which show increased activity against adult females of Aedes aegypti. The noreremophilanes and nardoaristolone B with hydrindane skeleton are structurally related to nootkatone with decalin skeleton, a well-studied natural product extracted from a grape fruit. Out of our library of compounds synthesized based on the noreremophilanes and nardoaristolone B scaffolds, NDS-100598 (compound 20) exhibits higher repellent and knock-down effects at a very low concentration (0.25 mg/cm2), while a few analogues showed considerably enhanced activity compared to racemic nootkatone. This is the first report documenting insect-repellent and knock-down activity of the noreremophilanes class of compounds.