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The cotton-melon aphid, <i>Aphis gossypii</i> Glover, is a polyphagous insect pest with many host-specialized biotypes, such as the Cucurbitaceae- and Malvaceae-specialized (CU and MA) biotypes. Bacterial symbionts were reported to determine the host range in some aphids. Whether this is the case in <i>A. gossypii</i> remains unknown. Here, we tested the host specificity of the CU and MA biotypes, compared the host specificity between the wingless and winged morph within the same biotype, and analyzed the composition of the bacterial symbionts. The reproduction of the CU and MA biotypes reduced by 66.67% and 82.79%, respectively, on non-native hosts, compared with on native hosts. The composition of bacterial symbionts was not significantly different between the CU and MA biotypes, with a <i>Buchnera</i> abundance >95% in both biotypes. Meanwhile, the winged morph produced significantly more nymphs than the wingless morph on non-native hosts, and the <i>Buchnera</i> abundance in the winged morph was only about 10% of that in the wingless morph. There seemed to be a relationship between the <i>Buchnera</i> abundance and host specificity. We regulated the <i>Buchnera</i> abundance by temperature and antibiotics, but did not find that a low <i>Buchnera</i> abundance resulted in the high reproduction on non-native hosts. We conclude that the host specificity of <i>A. gossypii</i> is not controlled by specific bacterial symbionts or by <i>Buchnera</i> abundance.