Abstract: The relationships were described in this paper between the Electrical Penetration Graphs (EPGs) of greenhouse whitefly,Trialeurodes vaporariorum (Westwood),and its probing, feeding and ovipositing activities. The potential application of this method in interpretating the resistance mechanisms against whitefly was also discussed.For whitefly adults, the A pattern and C pattern represent the probing initiation on the leaf surface and probing process in the mesophyll. The G pattern indicates xylem drinking and the E(pd), (1) & (2) are two different activities in sieve element and thus relate to phloem ingestion. Moreover, oviposition can be observed from EPG recordings, consisting of two subpatterns termed as Ovi-I and Ovi-II. For whitefly larvae, the H pattern indicates phloem ingestion but L pattern not, though still in sieve element. A procedure of styler withdrawal and repenetration occurs before and after moulting.

Key words: greeenhouse whitefly, EPG, probing, feeding, oviposition, moulting, resis- tance mechanisms