A larval specific OBP able to bind the major female sex pheromone component in Spodoptera exigua(Hübner)

Odorant binding proteins （OBPs） in insects are postulated to solubilize and transport the hydrophobic odorants across the hydrophilic antennal lymph to the olfactory receptors （ORs） located on the dendrite membrane of the sensory neurons. OBPs in adult insects have been intensively reported, but those in larvae are rarely addressed. In our study, a full-length OBP cDNA, namely SexiOBP13, was cloned by RT-PCR and RACE strategy from the heads of Spodoptera exigua larvae. The quantitative real-time PCR （qPCR） measurement indicated that SexiOBP13 was highly expressed in larval head, but very low in other parts of larva and was not detected in any tissues of adult. The binding affinities of SexiOBP13 to plant volatiles and female sex pheromone components were measured by competitive binding assays. Interestingly, SexiOBP13 displayed a high binding affinity （Ki=3.82 IJmol L-1） to Z9,E12-14：Ac, the major sex pheromone component of S. exigua, while low affinities to the tested host plant volatiles （Ki〉27 μmol L-l）. The behavioral tests further confirmed that Z9,E12-14：Ac was indeed active to elicit the behavioral activity of the third instar larvae of S. exigua. Taken together, our results suggest that SexiOBP13 may play a role in reception of female sex pheromone in S. exigua larvae. The ecological significance of the larvae preference to the adult female sex pheromone was discussed.

Female moths of cotton bollworm （Lepidoptera： Noctuidae） captured by waterbasin traps baited with synthetic female sex pheromone

Cotton bollworm, Helicoverpa armigera （Hüibner） （Lepidoptera： Noctuidae）, is one of the most important pest insects in cotton fields in China. Female moths were captured by waterbasin traps with a synthetic female sex pheromone blend in cotton fields over three years. The blend contained （Z）-11-hexadecenal and （Z）-9-hexadecenal with a ratio of 97：3. Each pheromone dispenser was impregnated with 2.0 mg of pheromone blend and 0.2 mg of antioxidant dissolved with 0.1 mL of hexane, and there was a control dispenser with a similar amount of antioxidant and solvent only. Waterbasin traps were deployed in three configurations in the fields. ‘A＇ was pheromone traps only, ‘B＇ was both pheromone and control traps, ‘C＇ was control traps only. （i） In four plots of ‘A＇, the average weekly female catch was 1.5, and more females were captured by centrally located pheromone traps. （ii） In three plots of‘B＇, control traps also captured female as well as male moths, but average weekly female catches of control traps was significantly lower than that in pheromone-baited traps. （iii） There were significant linear relationships between the average weekly female catch and the corresponding layer in pheromone-baited traps in both ‘A＇ and ‘B＇ plots, and in quadratic equations in control in ‘B＇ plots. （iv） With the increase of the interval of traps, average weekly female catches per trap increased but average weekly female catches per hectare decreased. （v） Among the female moths captured by pheromone traps, 88.3% were mated female moths which each containing 1.46 spermatophores, while in control traps 86.9% of the mated female moths had 0.90 spermatophores. There was a significant difference between the average numbers of spermatophores of mated females in pheromone traps and in controls.