Abstract: Transgenic Bt+CpTI cotton SGK321 and the parental cotton variety Shiyuan 321 were used to assess the predation function response and searching rate of Chrysoperla carnea (Stephens) on Aphis gossypii Glover. The results show that the instantaneous attack rate of C. carnea to A. gossypii increased with instar age. The instantaneous attack rates of 1st instar C. carnea to A. gossypii reared on SGK321 and Shiyuan321 were 0.045 and 0.044, respectively, and reached 0.107 and 0.093 at 3rd instar, respectively. The rates were not significantly different between different host plants. The feeding time of 1st instar C. carnea on A. gossypii reared on SGK321 and Shiyuan321 were 0.984 and 0.992 h, respectively, and 0.130 and 0.125 h at 3rd instar, respectively, which were also not significantly different between the host plants. With increase in prey population size, the maximum predatory amount in 24 h were not different between the host plants. The searching efficiency declined with increase in the number of A. gossypiii, from 0.0239 and 0.0235 to 0.015 and 0.0148 on plants of the two varieties for the 1st instar, respectively, from 0.0479 and 0.0464 to 0.0245 and 0.0242 for the 2nd instar, respectively, and from 0.0631 and 0.0588 to 0.0207 and 0.0207 for the 3rd instar, respectively. The present results reveal that transgenic Bt+CpTI cotton exerts no prominent effect on predation function response and searching rate of C. carnea.

Key words: transgenic cotton, Chrysoperla carnea, Aphis gossypi, predation function response, searching rate