Studies On Pheromones In Relation To Aggregation Outbreak Of Oedaleus Asiaticus B.-Bienko (Orthoptera: Acrididae)

Oedaleus asiaticus B.-Bienko(Orthoptera: Acrididae),one of the most dominant grasshoppers on steppes and agriculture-animal husbandry ecotones in northern China,occurred seriously in many areas in recent years. This species of grasshopper migrated as a vanguard and even swarmed into the centers of cities which rarely happened in the history. Therefore, studying the aggregation behavior of the grasshopper is crucial to explore the causes eliciting its outbreak. Here, we investigated the aggregation behavior of adult Oedaleus asiaticus from the point of semiochemicals both in the laboratory and in the field,and try to explore the main sources and chemical compositions of aggregation pheromones in order to characterize the active components of pheromones and exploit the environmentally-friendly managements through mediating aggregation behaviors by using pheromones in future. The main results are as follows:1. The adult of O. asiaticus showed less obvious aggregation behavior, which behaved in aggregation only in the period of young adults. The old female adults were also found to aggregate partially.2. The young or old female adults of O. asiaticus preferred to be within the airborne volatiles of live adults and feces of same sex but were indifferent to volatiles of male adults. Conversely,the young or old male adults of O. asiaticus preferred to be within the airborne volatiles of live adults and feces of same sex but were indifferent to volatiles of female adults,except the young male adults preferred to be within the airborne volatiles of females (young female feces) with same developmental stage as males.3. The behavior responses of O. asiaticus to different odours were not correlated to releasing ways of the grasshoppers(in groups of 5 or 10).4. The gravid females were found to oviposit preferentially in cups with eggs relative to in cups without eggs in a two-choice experiment. This suggests that the grasshoppers are able to use volatile cues to discriminate between cups with and without eggs, and can be attracted to to aggregate and oviposit by odours from egg pods and foams. These results preliminary showed that this species of grasshopper behaved in aggregative oviposition, and the egg pod and foam are possible sources of the primer pheromone mediating the ovipositing behavior of the grasshoppers.5. GC-MS analysis identified less compounds in the airborne volatiles trapped from live female and male adults of O. asiaticus, respectively. Benzenes, cycloalkenes, terpenes, and aldehydes were found in the volatiles of live female adults. Cycloalkenes and terpenes were contained in the volatiles of live male adults. The common compounds found in these two volatile samples wereα-pinene andβ-pinene.6. GC-MS analysis identified many compounds in the fecal volatiles from female and male adults of O. asiaticus, respectively. Ketones, aldehydes, and terpenes were found in the fecal volatiles of female adults. Esters, aldehydes, alcohols, cycloalkenes, ketones, and terpenes were present in the fecal volatiles of male adults. Aldehydes, ketones and terpene were common kinds of compounds in these two volatile samples. The composition of fecal volatile substances of female adult was much similar as one of male adult, sharing 2-methyl-propionaldehyde, 3-methyl-butyraldehyde, 2-methyl-butyraldehyde, andα- pinene.