A greenhouse study was performed to assess the damage and reproductive potentials of two thrips (Thysanoptera) species in relatively cool temperatures. Through measurements of plant biomass at the end of the study and visual plant damage ratings, the damage potential of tobacco thrips, Frankliniella fusca (Hinds), was found to be significantly less than that of the western flower thrips, Frankliniella occidentalis (Pergande), overall and on a per thrips basis. There were no differences found in the reproductive potential of either species on either of two cotton varieties. The results of this study confirm the importance of thrips identification since damage to cotton seedlings may be a function not only of the thrips density but also of the species involved.