Abstract: 【Objective】B and Q biotypes of Bemisia tabaci are two invasive cryptic species in China. The field investigation showed that Q biotype is becoming the dominant replacing B biotype in most areas of China in recent years. It is necessary to research the mechanisms and the influencing factor of the B. tabaci biotype replacement. Differences of feeding behaviors and competitiveness between B and Q biotypes of B. tabaci were compared under laboratory conditions, aiming to provide a basis for effective management of whiteflies. 【Method】 The stylet probing behaviors of B and Q biotypes of B. tabaci on Cucumis sativus were recorded and analyzed by using the electrical penetration graph (EPG) technique. The competitiveness of the two biotypes of B. tabaci was compared by investigating the population dynamics of the two biotypes in six successive generations on C. sativus. 【Result】 EPG results showed that B biotype B. tabaci had significantly more total number of probes (P=0.020) and longer total duration of probes (P=0.048) than Q biotype, and during the 2nd phase, the percentage of E was mainly lower (P=0.001) in B biotype than Q biotype, but there was no significant difference in percentage of probing duration between the two biotypes. Q biotype had significantly more total number of Pd (potential drop) (P=0.012) and longer total duration of Pd (P=0.016). For comparison of males and females in the same biotype, B biotype females were significantly lower than B biotype males in the percentage of Np (P=0.035) and the percentage of E (P＜0.001) during the 2nd phase, but females had significantly higher percentage of probe duration (P=0.011) than males. However, there was no significant difference in the duration of E(P＞0.05) in the 3rd phase between males and females of B biotype. For Q biotype, females not only had significantly higher percentage of probing duration (P=0.031) in the 2nd phase than Q biotype males, but also had significantly longer total duration of probes (P=0.039). Q biotype females had significantly shorter total duration of Np (P=0.038) than Q biotype males. There were no significant differences between males of B and Q biotypes for all EPG variables. For females whiteflies, B biotype had significantly more total number of individuals with E2＞10 min (P=0.036) than Q biotype, but Q biotype females had significantly higher percentage of E (P＜0.001) than B biotype in the 2nd phase. The results of the population dynamics of whiteflies on cucumber plants showed that the percentages of populations of the two biotypes became more and more divergent with the generations. In the 1st generation, the percentage of B biotype in the whole population almost reached 80%, and the percentage of the B biotype out of the whole population in the 5th generation and 6th already reached 98%. 【Conclusion】 Both the feeding ability and the competitiveness of B. tabaci B biotype were higher than those of Q biotype on cucumber without insecticide stresses in the laboratory, and those of females in either biotype of B and Q were higher than males.

Key words: Bemisia tabaci, B biotype, Q biotype, competitiveness, electrical penetration graph (EPG), host adaptation