Identification Of The Active Components From Fecal Volatiles Of Locusta Migratoria Manilensis

Aggregation behavior in the gregarious locust (Locusta migratoria manilensis) is mediated by a complex pheromone system released in the volatile emissions of their feces. My study focuses on the identification of the pheromones of fecal volatiles from locusts using EAD, GC-EAD, GC-MS, and locust olfaction equipment.GC-MS identified more than twenty compounds in the fecal volatiles of fifth instars including alcohols, aldehydes, ketones, heterogeneous-ring compounds. Over ten electrophysiologically active compounds were identified in the fecal volatiles by GC-MS and GC-EAD including Hexanal, Cyclohexanol, Hepanal, Nonanal, Guaiacol, 2,5-dimethyl-Pyrazine, 2,2,6-trimethyl-cyclohexanone, Benzaldehyde, Benzyl alcohol and 4-(2,6,6-trimethyl)-3-Buten -2-one. These compounds were found in both fifth instars and adults.Preliminary research on the EAG response and the behavioral response of locusts to compounds of fecal volatiles was investigated using GC-EAD and locust olfaction equipment. The electrophysiological bioassay showed that certain doses of 2,5-dimethyl-pyrazine (2mg) can cause significant EAG response in adult locusts. Higher (>3mg) or lower (<1mg) doses of 2,5-dimethyl-pyrazine cause no response.With Cyclohexanol, the EAG response of locust adults increases with increasing dose. The same dose of different compounds cause the different EAG responses. Male adult locusts are more sensitive than females to similar doses (4mg) of the same compound.Behavioral bioassays showed that certain concentrations of nonanal (40-50ul/ml) are significantly more attractive to 5th instar locust nymphs. Higher (>50ul/ml) or lower (<30ul/ml) concentrations of nonanal cause no response.2,5-dimethyl-pyrazine at a concentration of 20-25ul/ml has a high attraction for fifth instars. However, higher concentrations (>40ul/ml) had repellent effect and there was had no response to lower concentrations (<15ul/ml). Similarly, >25ul/ml of Cyclohexanol results in significant aggregation response of 5th instars, while low concentrations (<20ul/ml) cause no response.With Benzaldehyde, certain concentrations (10-20ul/ml) results in significant aggregation response of 5th instars, while higher (>30ul/ml) or lower (<5ul/ml) concentrations cause no response. These results show that there is a wide range of chemicals in fecal volatiles. These compounds are often only attractive at certain concentrations, which may prove to be very important in the aggregation behaviours of locusts.