This study was conducted to better understand the life history of Parthenolecanium corni (Bouché) and Parthenolecanium quercifex (Fitch) (Hemiptera: Coccidae), and to develop degree-day models for crawler emergence of the two soft scale species in Georgia, North Carolina, South Carolina, and Virginia. Both species were univoltine in the southeastern United States. In South Carolina, eggs hatched from mid-April to early June; second instars began to appear in September and migrated to twigs to overwinter in October; and third instars and adults appeared in mid-March to early April. Each parthenogenetic female produced on average 1,026 ± 52 eggs. Fecundity was positively correlated to the fresh weight, length, width, and height of gravid females. Gross reproductive rate (GRR) was 695.98 ± 79.34 ♀/♀, net reproductive rate (R°) was 126.36 ± 19.03 ♀/♀, mean generation time (TG) was 52.61 ± 0.05 wk, intrinsic rate of increase (r_m) was 0.04 ♀/♀/wk, and finite rate of increase (λ) was 1.04 times per week. Crawlers first occurred across Georgia, North Carolina, South Carolina, and Virginia in 2011–2013 when 524–596 Celsius-degree-days (DDC) had been accumulated with the single sine estimation method, or 411–479 DDC with the simple average method, at the base temperature of 12.8 °C and the start date of 1 January. These regional models accurately predicted the date of crawler emergence within 1 wk of the actual emergence in 2014.