As a generalist predator, Orius similis can prey on thrips, aphids, spider mites, whiteflies, eggs and newly hatched larvae of Lepidoptera pests, and therefore O. similis is considered as a very promising valuable natural enemy agent because of its long occurring time, high population, a wide range of preys, strong adaptability and high predation. O. similis is a predominant predatory nature enemy species in South China and plays an important role in suppressing the population of many pests. Studying on the biological and ecological characteristics of this natural enemy is the basis for utilization of the predator in biological control of the pests.
In the present study, Frankliniella occidentalis (Pergande), Aphis craccivora Koch, Tetranychus urticae Koch and Tyrophagus putrescentiae Schrank were used as preys to determine their effects on the development and fecundity of O. similis. The results showed that the newly-hatched nymph of O. similis, which is feeding on T. putrescentiae, could only develop to its 5^th instar nymph, rather than to adult stage, with the accumulated survival rate of its 4^th instar nymph as low as 6.8%, while O. similis can develop and reproduce successfully on the other three prey species. The development duration, survival rate, and reproductive characteristics of O. similis were significantly different among preys. With F. occidentalis as prey, O. similis had the shortest immature development duration with 16.2d, about 6 days shorter than that of O. similis feeding on other two preys. O. similis had the highest fecundity with 65.7 per female feeding on F. occidentalis, while O. similis had the longest development, lowest fecundity when feeding on T. urticae. According to the reproduction of first generation of O. similis fed on 3 preys species, the fecundity specific life tables of O. similis were constructed and the parameters were calculated. The net reproductive rate (R₀) was highest up to 26.6632 while fed on F. occidentalis, which was as 5.7 and 7.7 times as those fed on A. craccivora and T. urticae respectively. Furthermore, feeding on F. occidentalis, r_m, λ of O. similis were significantly higher than that of fed on either of other two prey species. The results indicated that F. occidentalis was the most suitable prey for increasing the population of O. similis under the laboratory conditions. When O. similis were fed with different prey species for two generations continuously, the development and fecundity of second generation of O. similis feeding on three prey species were similar to that of first generation. Differences were found in development and reproduction of O. similis between the first generation and the second generation, and the differences were correlated with the prey species. The immature time declined from 22.2d of the first generation of O. similis to 19.2d of the second generation while feeding on A. craccivora, and the fecundity was not significantly different between two generations. The similar results were found when O. similis was fed with T. urticae for two generations continuously, and the immature time declined from 22.6 d of the first generation of O. similis to 17.0d of the second generation, however, the fecundity of the second generation was lower than that of the first generation. No significant differences were found between the two generations while feeding on F. occidentalis. In conclusion, our results indicated that F. occidentalis was the best prey for the development and fecundity of O. similis.