Abstract:

The bionomics of two parasitoids Encarsia Formosa and En. sophia on Bemisia tabaci and host competition between the two parasitoids were investigated in the laboratory. The results indicated that there were no significant differences in length of hind leg tibia between two parasitoids. The ovipositor and egg size of En. sophiawere longer than those of En. formosa, and eggs ready to be laid by one-day old female wasp of En. Sophia was less than those of En. formosa. The time taken by En. Sophia in both host checking and ovipositing were significantly shorter than that of En. formosa, whereas the rounds turned during host checking by a wasp of En. Sophia were less than those by a wasp of En. formosa. The developmental time of En. Sophia egg was about 24 h, which was significantly shorter than that of En. Formosa egg. The pupal duration of En. Sophia was also significantly shorter than that of En. formosa. The developmental time from egg to adult for En. Sophia was about 72 h shorter than that for En. formosa. In 24 h, the total oviposition in combination treatment of one En. formosa and one En. Sophia was 14.0 eggs, which is more than that in combination treatment of two En. formosa (10.2 eggs) and significantly more than that in combination treatment of two En. Sophia female wasps (9.5 eggs). The mean number of eggs loaded in parasitized host in combination treatment of two wasp species (1.73 eggs) was significantly higher than

that in combination treatment of females from one wasp species, which were 1.29 and 1.39 eggs for En. formosa and En. sophia, respectively. In combination treatment of two wasp species, the numbers of eggs laid in host parasitized by two wasp species were 1.21 and 1.43 for En. Formosa and En. sophia, respectively, and were significantly more than those in the hosts parasitized by only one wasp species, which were 1.06 and .19 for En. Formosa and En. sophia, respectively. The results suggest that female wasps of both En. Sophia and En. Formosa can recognize the existence of another species, and En. Sophia has higher competence than En. formosa.

Key words: Bemisia tabaci, Encarsia formosa, Encarsia sophia, bionomics, host competition