Influence of temperature on the biology of Aenasius arizonensis (Girault) (Hymenoptera: Encyrtidae), a parasitoid of solenopsis mealybug, Phenacoccus solenopsis Tinsley

摘要

Effect of temperature on the biology of Aenasius arizonensis (Girault) (=Aenasius bambawalei Hayat) (Hymenoptera: Encyrtidae), a parasitoid of solenopsis mealybug, Phenacoccus solenopsis Tinsley, was studied at four constant temperatures viz. 20±1, 25±1, 30±1 and 35±10C. Mealybugs were reared on sprouted potatoes. The parasitoid completed its development at all the temperatures studied and males developed faster than the females. For males and females, respectively, total development period was 30.56, 24.16, 13.40 and 11.60 days and 34.40, 26.20, 14.88, and 12.04 days at 20±1, 25±1, 30±1 and 35±10C, respectively. The daily and total fecundity (number of hosts parasitised) was 1.42, 1.82, 3.17, 2.16 and 57.13, 63.15, 65.60, 37.46 at 20±1, 25±1, 30±1 and 35±10C, respectively. Female parasitoids parasitised mealy bugs on the day of emergence at all the temperatures. At respective temperatures oviposition and post-oviposition periods were 35.86, 33.60, 18.93, 15.53 days and 2.86, 2.26, 2.60 and 2.33 days, respectively. Parasitoid males were short lived as compared to females at all the temperatures. The male and female longevity, respectively, was 23.06, 17.26, 13.20, 10.33 days and 38.66, 34.53, 20.86, 17.86 days at 20±1, 25±1, 30±1 and 35±10C, respectively. Sex-ratio (male: female) was in favour of female parasitoids (1: 1.1 to 1: 1.2) at all the temperatures. Net reproductive rate (36.41), intrinsic rate of increase (0.155) and finite rate of increase (1.168) were maximum at 30±10C indicating this temperature to be the most favourable for the development and reproduction of the parasitoid. Males emerged out from the small sized mummies (2.28×1.20mm) whereas; large sized mummies (2.90×1.59mm) yielded mostly the female parasitoids. Males were generally smaller in size (1.26×0.58mm) as compared to female parasitoids (1.84×0.89mm). The results of the present studies could be useful in establishing a mass rearing programme for the parasitoid.