Age-stage, two-sex life tables of Bactrocera cucurbitae (Coquillett) (Diptera: Tephritidae) with a discussion on the problem of applying female age-specific life tables to insect populations

Age-stage, two-sex life tables of the melon fly, Bactrocera cucurbitae (Coquillett) (Diptera: Tephritidae), reared on cucumber (Cucumis sativus L.), sponge gourd (Luffa cylindrica Roem) and a carrot medium (mashed Daucus carota L. mixed with sucrose and yeast hydrolysate) were constructed under laboratory conditions at 25 +/- 1 degrees C, 65%+/- 0.5% relative humidity, and a photoperiod 12 : 12 h (L : D). The intrinsic rates of increase of B. cucurbitae were 0.144 6, 0.141 2 and 0.068 8 days on cucumber, sponge gourd, and carrot medium, respectively. The highest net reproduction rate was 172 offspring per fly reared on sponge gourd. The mean generation times of B. cucurbitae ranged from 34 days reared on cucumber to 56 days reared on carrot medium. The life history raw data was analyzed using the traditional female age-specific life table and compared to results obtained using the age-stage, two-sex life table. When the age-specific female life table is applied to an age-stage-structured two-sex population, survival and fecundity curves will be improperly manipulated due to an inability to include variation in preadult development time. We discussed different interpretations of the relationship between the net reproductive rate and the intrinsic rate of increase to clarify possible misunderstanding in the literature.