Mortality and developmental rates of the cotton fleahopper,Pseudatomoscelis seriatus(Reuter), were affected by the species and maturity of host plants. Survival was higher and development was faster onCrotonsp. than on other hosts such as spotted beebalm,Monarda punctataL., cutleaf primrose,Oenothera laciniataHill, and cotton,Gossypium hirsutumL. Also, survival and development rates were higher on flowering plants than on plants in a preflowering growth stage.Predictions of fleahopper development based on temperature data were affected by the host plant. Heat units required for total nymphal development varied from 98.2°C days on flowering croton to 163.2°C-days on preflowering cutleaf primrose.