Sipha flava is a serious pest in sugarcane in southern Florida, so efforts in better understanding its biology were initiated. Development, longevity, and fecundity of alate and apterous S. flava (Forbes) feeding on Sorghum bicolor [L.] Moench., cultivar ‘Kow Chow,’ were examined under near-ambient temperature and lighting conditions within a glasshouse. After examining several body dimensions during apterous aphid development (antennal length, head width, body length, and abdominal width), antennal length was found to be the best indicator of an instar. Apterous aphids completed development from nymph to adult in ≈8 d and passed through four instars. A comparison between the sizes of apterous and alate morphs indicated that apterous females were larger and weighed more than the alates. Both morphs survived equally as long during reproduction (21 d) but produced slightly different numbers of nymphs over their life (apterous = 54.3, alate = 48.2). During the first 8 d of reproduction, apterous adults produced 3.3 nymphs/d and alates produced 2.3 nymphs/d. However, during the following 8 d, nymphal production by apterous females dropped to 2.7 nymphs/d but increased to 2.9 nymphs/d by alates. The estimated intrinsic rate of natural increase (r_m) for apterous aphids was 0.314. The net reproductive rates (R_o) for alate and apterous adults based on 0% nymphal mortality were 45.80 and 53.09 and for 21% nymphal mortality were 36.3 and 41.9, respectively.