Studies On The Biology And Ecology Of Opius Caricivorae Fischer (Hymenoptera: Braconidae), A Parasite Of Liriomyza Sativae Blandchard (Diptera: Agromyzidae)

Opius caricivorae Fischer is a major larval-pupal endoparasitoid of Liriomyza sativae Blandchard. The biology and ecology of this parasitoid were studied under laboratory condition by using L. sativae on the bean Phaseolus vulgaris L. as the host.The larvae of O. caricivorae underwent six instars. The 1 st instar larvae were mandibulate while the larvae of other five instars were hymenopteriform. The 1 st instar larvae could attack each other. The 6th instar larvae spun a cocoon in the host pupa where it pupated. The morphological characters of the parasitoid larvae of each instars were described in detail.The adult parasitoids emerged by daylight with a peak at 8:00-10:00. About 91% of the adults mated on the emergence day. Female-biased adult sex ratio was found in laboratory populations ( : = 1.51:1). Longevity of both female and male adults decreased with increase of temperatures from 17 to 33 when honeybee solution was provided. Mean longevity of females was longer (81 d at 17 and 14 d at 33 ) than that of males (47 d at 17 and 13 d at 33 ). Female adults started oviposition on 1-2 d after emergence with a peak on 2-7 d from 21 to 29 . The relationship between average fecundity and temperature could be fitted with the equation y = -0.057x2 + 2.728x - 20.601 (r2 = 0.934). The females were able to kill hosts by feeding. In addition, the host-feeding, oviposition and host-searching behaviors of the parasitoids were described.The developmental and survival rates of the egg, larval and pupal stages were measured at 5 constant temperatures of 17, 21, 25, 29and 33 . The results showed that the linear Degree-Day and the Logistic models could describe well the relationship between the development rate of each immature stage and the mid temperatures. The development durations of egg, larva, pupa and egg-pupa varied from 2.54 to 7.69, 0.50 to 2.73, 7.24 to 13.09, 14.47 to 32.43 days, respectively. The development temperature threshold for pupa was 1.60癈 with effective accumulated temperatures 208.33 day-degree, suggesting that the parasitoid could overwinter by pupa in the field. The development temperature thresholds for egg, larva and egg-pupa were 11.48, 7.74-12.80 and 8.03 with effective accumulated temperatures 41.32, 10.27-17.89 and 303.03 day-degree, respectively. About 69.8 percentage of pupae underwent dormancy at or above 33 . The relationship between survival rate and temperature could be fitted with the equation S = -0.009T2 + 0.4107 - 3.872 (R = 0.9583). The survival rates of the egg and larvae were more than 89.6% and 81.3%, respectively. Pupal survival rate varied greatly from 8.7% at 33 to above 83.0% from 17 to 29 .The net reproduction (R0) peaked at 21 and declined both above and below this temperature. However, both the intrinsic rate of increase (rm) and finite rate of increase ( ) increased from 17 to 29 and decreased from 29 to 33 . The intrinsic rate of increase (rm) at 21 or 25 nearly doubled compared with that at 17 . The relationship between thepopulation growth index (I) and temperature (T) was described by the equation: / = -0.904T2 + 41.1667 - 374.320 (R2 = 0.993). The population growth index (7) was highest (94.21) at 25 but lowest (0.78 <1) at 33 . The results indicated that the population of O. caricivorae decreased at or above 33 .O. caricivorae parasitized more host larvae of 60-h-old than those of 24-h-old or 36-h-old with the 24-h-old host larvae the least. The parasitoid preferred 36-h-old host larvae for feeding. The sex ratio of O. caricivorae population emerged from 60-h-old larvae parasitized was not higher than those from 24-h-old larvae parasitized, and nearly around 1.54:1 in average.O. caricivorae heavily feed on host larvae. The numbers of the host larvae fed by the parasitoid increased linearly with the host density from 20 hosts/leaf to 60 hosts/leaf. The mortality due to the host-feeding increased with the increase of parasitoid densities from 1 to 5. The results showed that conspecific superparasitism occurred, and depended...