Aphid body size
The nymphs of the HI lineage cultured on pre-infected cucumber for the first generation developed into big green morphs (Figure 2D), while those cultured on fresh cucumber developed into tiny yellow dwarfs (Figure 2C). The big green morphs were significantly bigger than the tiny yellow dwarfs in body length or wide (p <0.001) (Figure 2A,B). Body size differences of the HI lineage cultured on pre-infected and fresh cucumber for the third generation were still significant (p <0.001) (Figure 2E,F). Both the HI lineage who had feeding experience on pre-infected cucumber and the CU lineage developed into the same green big morphs on fresh cucumber (p >0.05) (Figure 2G,H).
Piercing and sucking behaviors
Duration of C and E1 waveforms of the HI lineage on pre-infected cucumber were not different from that on fresh cucumber significantly (p =0.076 and 0.085 respectively) (Figure 3A,B). However, duration of E2-waveforms of the HI lineage on pre-infected cucumber was significantly longer than that on fresh cucumber (p <0.001) (Figure 3C), even as long as that of the CU lineage on fresh cucumber (p =0.431) (Figure 3C). Duration of G waveform of the HI lineage on fresh cucumber was not significantly different from that on pre-infected cucumber (Figure 3D) (p =0.510). Piercing and sucking behaviors indicated that the HI lineage did not ingest phloem sap from fresh cucumber, but did ingest phloem sap from pre-infected cucumber, which explained why the HI lineage performed badly on fresh cucumber but very well on pre-infected cucumber.