Host instar suitability of Bemisia argentifolii (Homoptera : Aleyrodidae)for the parasitoid Encarsia pergandiella (Hymenoptera : Aphelinidae)

摘要

Studies were conducted to assess the suitability of instars of Bemisia argentifolii Bellows & Perring attacked by Encarsia pergandiella Howard. E. pergandiella parasitized all instars of B. argentifolii, although the rate of parasitism of second, third, and early- or late-fourth instars was significantly greater than for first-instar hosts. The highest percentage of parasitoid emergence (96.3%) was when third instars were parasitized, and the least (69.4%) when first instars were attacked. The second, third, and early-fourth-instar hosts resulted in the higher proportion of host mortality and parasitoid survival. Parasitoids took significantly longer to develop after parasitizing first instars (14.9 d) than after parasitizing other instars (11.0-12.0 d). The shortest period of progeny emergence (2.0 d) occurred when E. pergandiella had parasitized the third instar. The longevity of unfed progeny was significantly longer (2.3-3.0 d) for adults emerged from hosts attacked at the third or early fourth instar compared with those following parasitization of first (1.5 d), second (1.9 d), or late-fourth (1.4 d) instars. When E. pergandiella parasitized the first or late-fourth instars, emerging females were significantly smaller (0.437-0.444 mm) compared with those emerged from other instars (0.483-0.495 mm). When E. pergandiella parasitized first, second, or third instars, the parasitoid can be referred to as a koinobiont because after parasitization, the host continues to feed, grow, and develop. When E. pergandiella parasitized early- or late-fourth instars, however, the hosts seemingly stopped development (idiobiont).