This study was held in two experimental sites belonging to the Tunisian Eastern Central Coast. Frankliniella occidentalis Pergande 1895 (Thysanoptera; Thripidae) males and females counting during the study period using two sampling methods; blue sticky traps and sampling of flowers, showed that differences between both sexes tends gradually to rise approaching hot season with a continuous increase of females' number till the end of prospecting. These differences between both sexes affected the sex ratio recorded on flowers and blue sticky traps which tended to decrease progressively from 0.13 and 0.15 to 0.02 and 0.009 in pepper flowers in the biotope of Bekalta, from 0.11 and 0.14 to 0.08 and 0.06 in pepper flowers and 0.37 to 0.19 on blue sticky traps in the biotope of Moknine. Biotic and abiotic parameters in the greenhouses had an impact on sex-ratio tendency; more climatic conditions and pepper flowers' number improve and thrips density becomes higher, more sex-ratio tends to decrease. The apical stratum of pepper crop had the highest sex-ratio and males, females and total thrips number with often significant differences with the other strata (central and basal). Same as for blue sticky traps where sex-ratio was higher than in pepper flowers with significant differences.