F.-P. Zhang’s research while affiliated with Chinese Academy of Tropical Agricultural Sciences and other places

Metaphycus parasaissetiae is a dominant endoparasitoid found in Parasaissetia nigra adults; however, various factors influence the efficiency of the parasite. The parasitic rate, emergence amount per host, and the sexes of its progeny were used to evaluate the effects of temperature, photoperiods, ages of P. nigra adults, adult ages, and female M. parasaissetiae mating success on parasitic efficiency. The results showed that the parasitic rate peaked (91.7%) at 27—30 °C, but decreased to 88.3% at 33 °C. In the temperature range of 21 to 27 °C, the emergence levels of M. parasaissetiae gradually increased with temperature, increasing 7.5 at 27 t. This emergence level was significantly higher than that recorded at other temperatures. However, in the temperature range of 27 to 33 °C, the emergence level decreased with temperature, declining to 5.1 at 33 °C. The highest female ratio was 72.1% at 24 °C, followed by 62.6% at 27 °C; thus, a temperature range of 24 to 30 °C is suitable for the parasitoid. Parasitic efficiency gradually increased as the illumination duration was increased from 8 h to 12 h. After 12 h illumination, the number of parasitized hosts, parasitic rate, emergence level, and female progeny ratio of M. parasaissetiae were the highest in all groups, i.e., 21.2, 70.6%, 5.3, and 68.3%, respectively. However, these factors decreased after 16 h illumination, i.e., 9.0, 30.0%,1.7, and 34.1%, respectively. In parasitized P. nigra adults aged 20 and 21 days, the highest parasitic rate (87.0%), number of emerging parasitoids (5.6), and female progeny ratio (51.2%) of M. parasaissetiae was recorded. In comparison, in parasitized hosts aged 1 and 2 days, these factors were 33.0%, 0.9, and 46.6% respectively. This result indicates that adult P. nigra hosts aged 20 and 21 days are the most compatible for M. parasaissetiae, while those aged 1 to 2 days were not optimal. The age of female parasitoid adults represented another important factor that influences the parasitic efficiency of M. parasaissetiae. The number of parasitized host, emergence level of the offspring, and parasitic rate increased with the age of female adults (in the age range of 2-4 days), reaching 16.3, 5.2, and 81.7%, respectively, at 4 days. These values were higher than those observed at ages 2, 6, 7, and 8 days. In M. parasaissetiae females of >4 days of age, the number of parasitized hosts and parasitic rate decreased gradually. At the age of 8 days, the lowest parasitic ratio, emergence level, and number of parasitized hosts was recorded, i.e., 25.0%, 1.5, and 5, respectively. However, the ratio of female offspring was the highest (55.2%) at 5 days. Mating also significantly affected the parasitic efficacy and sex ratio of M. parasaissetiae. The parasitic rate (91.7%) and emergence (7.5) induced by mated parasitoids were greater than that by unmated parasitoids. The female ratio of mated female parasitoid offspring was 62. 1%, whereas unmated females produced no female offspring. We concluded that a combination of factors are required for the optimum conditions for M. parasaissetiae, including P. nigra adults aged 20-21 days, mated female parasitoids aged 3 - 6 days, temperature conditions of 27 °C, and a light: dark photoperiod of 12:12 h.

Metaphycus parasaissetiae Zhang & Huang (Hymenoptera: Encyrtidae) is an important adult parasitoid of Parasaissetia nigra Nietner (Hemiptera: Coccoidea). The external morphology of the antennal sensilla of male and female M. parasaissetiae was examined using scanning electron microscopy. The geniculate antennae of male and female M. parasaissetiae were composed of a scape with a basal radicula, a barrel-shaped pedicel, and a long flagellum. Twelve morphologically distinct types of sensilla were identified, including multiporous placoid sensilla, campaniform sensilla, finger-like sensilla, multiporous basiconic sensilla (BS-1), three aporous types of basiconic sensilla (BS-2, BS-3, and BS-4), two types of aporous trichoid sensilla (TS-1 and TS-3), a type of multiporous trichoid sensilla (TS-2), and two types of sensilla chaetica (CH-1 and CH-2). Sex dimorphism in the sensilla composition of M. parasaissetiae is also observed. Major differences between the sexes were found in the number, distribution, shape, structure, and size of the identified sensilla. We also discuss on the functional aspects of these sensilla to elucidate the mechanisms involved in host searching and courtship behavior of M. parasaissetiae.

The study on the predatory functional responses of Stethorus parapauperculus to Tetranychus piercei adults at 16 °C , 20 °C , 24 °C , 28 °C and 32 °C showed that within the range of test temperatures, the predatory functional responses of female S. parapauperculus adults could be simulated by Holling type II , but the coefficients varied with temperature. Taking the successful attack rate and handling time as evaluation indicators, the predation efficiency of female S. parapauperculus adults on T. piercei adults within the range of 16 °C-28 °C increased with increasing temperature, and reached the maximum at 28 °C. At 32 °C , the predation efficiency decreased slightly. The successful attack rate and handling time at 32 °C were 0.5740 and 0.0184 day, respectively, which had no significant differences with those (0.5899 and 0.0169 day, respectively) at 28 °C , indicating that higher temperature was favorable to the control effect of S., parapauperculus on T. pierceii. A cubic polynomial equation was derived to describe the effects of temperature and prey density on the predation rate of female S. parapauperculus adults, and a contour plot of the estimated predation rate for any combinations of test temperature and prey density was produced by Surfer 8 software. The implication of these results for the biological control with S. parapauperculus against the pests on tropical crops was discussed.