Life tables of cotton aphid (Aphis gossypii Glover) fed on three cucurbit varieties and the effect of host plant transferral

The life tables of the cotton aphid, Aphis gossypii (Hemiptera, Aphididae), were investigated for individuals fed on three different cucurbit varieties, Lagenenaria siceraria, Cucumis sativus, and C. melo.  All studies were conducted at 20~30°C.  The effects of host plant transferral between taro and cucurbit plants on the survival of cotton aphids were also investigated.  When taro-fed alates were transferred to any of the three Cucurbitaceae plants, all adults and their offspring had succumbed within a five day period.  Results indicated that the longest developmental time was found for aphids reared on C. sativus.  The developmental time decreased from 9.09 to 4.6 days when temperatures were increased from 20 to 30°C, while the adult longevity was shortened from 22.84 to 11.6 days.  At 20°C, aphids that fed on L. siceraria had the highest net reproductive rate (87.92 offspring); followed by those reared at 25°C and fed on C. sativus (77.65 offspring).  The lowest value occurred in aphids reared at 30°C on L. siceraria (49.39 offspring).  The highest intrinsic rate of increase (r) and the finite rate (λ) were observed for aphids reared on L. siceraria.  The values of r and λ increased with temperature, while the mean generation time (T) was shortened as the temperature increased.  Aphids fed on L. siceraria under 20-30°C had shorter T values than those that fed on the other two cucurbit plants.