Reproduction of Aphelinus albipodus (Hymenoptera: Aphelinidae) on Russian wheat aphid (Hemiptera: Aphididae) hosts
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abstract
Reproduction in Aphelinus albipodus (Hayat & Fatima) from China on Diuraphis noxia (Mordvilko) hosts was studied in the laboratory. Studies were conducted at three constant temperatures, 10.0, 21.1, and 26.7C ( 1.0C), 14L : 10D photoperiod, and 50-70% R.H. The longevity of both males and females was greatest at 10.0C (26.0 and 41.5 d, respectively); differences in longevity were not significant (p > 0.05) between 21.1 and 26.7C in both sexes (males 13.1 vs. 10.0 d, females 20.9 vs. 16.4 d, respectively). Fecundity was greater at 26.7 (294.7 27.6 mummies) and 21.1C (214.8 33.5 mummies) than it 10.0C (56.9 11.7 mummies), but was not significantly different (p > 0.05) between the former two temperatures. Aphelinus albipodus did not successfully develop to adulthood at 10C, thus rmand Rovalues were zero, and Tc(generation time) could not be estimated. At 21.1C, rm= 0.188, Ro= 68.9, and Tc= 23.9 d; those values were 0.288, 67.4, and 15.2 d, respectively, at 26.6C. The offspring sex ratio (females) was male-biased at all three temperatures: 0.364 0.061 at 10.0C, 0.437 0.029 at 21.1C, and 0.341 0.002 at 26.7C. Moreover, daily offspring sex ratio decreased with the age of the female parent at all three temperatures (p < 0.05). A pre-oviposition period of 1.5 d was observed in A. albipodus at 10C, and female offspring were not produced during the first 7.5 d of adult life of mated females. The limited number of ovarian eggs, 6.5 2.5, in newly emerged females (< 6 h old) together with their fecundity schedule indicated synovigeny in A. albipodus. Results are discussed in relation to the colonization in North America of A. albipodus for biological control of D. noxia.
