Abstract: The cotton aphid populations are differentiated in food utility, and the host fidelity has been found all over the world. The morphometric differentiation and ecological adaptabilities of cotton and cucumber biotype aphids were studied used such methods as morphometric analysis, life table, host selection test, and stimulating aphid with a needle. The results showed that the examined morphometric values of the cucumber biotype aphid were significantly higher than that of the cotton biotype aphid, but the ratios of head width, stylet and the femur to body length of the cucumber biotype aphid were significantly lower than that of the cotton biotype aphid. The cucumber and cotton biotype aphids could be distinguished through the discrimination analysis with the indices such as the relative lengths of head, abdomen tube, stylet, femur length of fore-, mid- and hind-leg, and the 3rd segment of antenna to body length. The net reproductive rate of the cucumber biotype aphid reared at 24℃ and 26℃ was significant higher than that of the cotton biotype aphid, but the mean length of a generation was significantly shorter at 27℃ and 32℃. This suggested that the relative lower temperature was more suitable to the cucumber biotype aphid for development and reproduction, and the relative higher temperature was more suitable to the cotton biotype aphid. The response of the cotton biotype aphid to the touch with a little needle was slightly stronger than that of the cucumber biotype aphid. The capacity of the cucumber aphid to orient and select host plant was higher than that of the cotton biotype aphid. The results indicated that the morphometrics and ecological adaptability of the cotton and cucumber biotypes were differentiated

Key words: Aphis gossypii, host biotype, morphometrics differentiation, ecological adaptability