Survival Characteristics And Reproductive Characteristics Of Bradysia Odoriphaga Yang Et Zhang

1. Effect of temperature on growth, survival and reproduction of Bradysia odoriphagaExperiments were carried out to determine the developmental durations, life-spans of four stages of Bradysia odoriphaga and its fecundity at different temperatures, indicating that the suitable temperature range for its development was 20℃-25℃. At the lower temperature (10℃-15℃), it grow slowly, but reproduce normally. However, when the temperature was above 30℃, the development and reproduction can be inhibited seriously. There were no evident effect of temperatures(10℃-30℃) on the fecundity. The temperatures for growth of the fungus gnat was similar to that for growth of chives, showing that Bradysia odoriphaga can adapt to its host's growing condition well.The developmental zeroes and the effective accumulated temperatures of eggs, larvae and pupae were determined according to the development duration at 10℃, 15℃, 20℃, 25℃and 30℃. Based on the effective accumulated temperatures, 8-9 generations may occur in Taian one year.2. Life table of laboratory populations of Bradysia odoriphagaThe specific age life table of laboratory population of Bradysia odoriphaga were established at 20℃and 25℃. The key death stages was the newly-hatched larva and pupae which were the weak stages in the development. According to the analysis of survival curves, the death rates of the fungus gnat was very low. All the individuals in the population could reach their physiological life-span, showing their high survival ability. According to the analysis of trend index of population, the number of next generation's population would increase as much as 69.93 times and 69.78 times at the temperature of 20℃and 25℃, respectively. At the two temperatures the sex ratio was 1.1:1 and 0.9:1, respectively, which were all close to 1:1.3. The circadian rhythm of adult emergence and activity rhythm of adults in fieldsThe circadian rhythm of emergence The emergence of female and male in spring and autumn obviously showed a circadian rhythm. The number of emergence increased from 5:00pm until 23:00, peaking from 23:00 to 6:00am, while decreasing from 7:00am to 5:00pm. This study can provide important information and foundation for when the sex pheromone of adult was extracted.The activity rhythm of adults in fields Trial showed that activity of adults in fields in daytime was exhibited in a rhythm, peaking from 9:00am to 13:00pm, especially from 9:00am to 11:00am. The activity rhythm of adults in fields can give great help to adult control.4. Extraction of sex pheromone of Bradysia odoriphagaThe sex pheromone extracted by the method of menstruum-extracting and filter paper-collecting can induce strong and typical courtship behavior. According to bioassay, the lure of over 20FE can effectively induce male adults. The results in laboratory and field indicated that the sex pheromone are volatile greatly, not persistent in inducing male adults and the attracting distance was also short, so it can not be used in forecasting or traping male adults directly. But the methods of extracting sex pheromone can help further study of the component and chemical structure of sex pheromone.5. The reproductive strategy and the reproductive potential210 couples of female and male were mated and the offsprings of each couples were cultured till pupation and emergence. And then the individual number of female and male were counted. Among 210 couples, 78.57% of couples gave birth to monosexual progeny (female or male); 21.43% bisexual progeny, but unbalanced in the ratio of female to male; 0.95% the progeny with equal sex ratio. The reproductive strategy of Bradysia odoriphaga reduce the frequency of reproducing bisexual progeny as far as possible. The ecology mechanism of this behavior consists mainly in avoiding intermarriage in order to keep this population thriving. So this reproductive strategy was a kind of evolutionarily stable strategy.Six male adults mated separately with several female adults, one male adult can mate with 8-10 female adults which can lay all their eggs down. If each female adult can lay 167.85 eggs (the mean fecundity obtained as above )and each male adult can contribute 1342.8-1678.5 spermatozoons for eggs, indicating that the reproductive potential was high.