Quantitative feeding behaviors were analyzed by electronic penetration graph technique to evaluate the resources utilization efficiency of the solenopsis mealybug, Phenacoccus solenopsis (Tinsley) (Hemiptera: Pseudococcidae), transferred to a novel host. Both nonphloem and phloem factors were contributed to the host availability during host shift; while only “prephloem” factor was involved with their offspring’s fitness to the transferred host, on which they fed as effectively as their mothers did on the origin host. Different performances on different hosts were supposed to have relations with the diverse phloem components, rather than feeding behaviors. P. solenopsis could try and exploit an efficient stylet pathway to reach the phloem, which would be an importance factor to account for the expansion of the host range and adaptations to different hosts. High efficient feeding behaviors of P. solenopsis in the current study manifested its capability of resource utilization to the novel host, which was suggested to be advantageous for its host shift, and to be the explanation for rapid host shifts associated with its broad host range and quick settlement.

Imidacloprid application, as a seed coating agent on oilseed rape, is recommended to control mustard aphid, Lipaphis erysimi (Kaltenbach) (Hemiptera: Aphididae). In this study, responses of L. erysimi were investigated, including survival, feeding behavior, and detoxifying enzymes, on the oilseed rape seedlings grown from seeds coated with imidacloprid at rates of 6, 12, or 18 g active ingredient (a.i.)/kg seed. The results showed that the aphids’ survival rate, together with that of the progeny of the survivors, on the seed-treated seedlings significantly decreased. This indicates that the aphid population in fields can be suppressed effectively. The electrical penetration graph (EPG) technique was used to record aphid feeding behaviors on two-, four-, and six-leaf stages of oilseed rape seedlings that had been seed-coated with imidacloprid, and individual responses were revealed during the aphid feeding behavior. On the plants at the two-leaf stage, aphid feeding behaviors were influenced, showing decreased frequency of stylet penetration into the leaf (probe) or into the mesophyll cells (potential drops, pds for short), and shortened duration of stylet event in the leaf (probe) or in the phloem. On the plants at the four- and six-leaf stages, these impacts of imidacloprid were weakened; however, the saliva secretion duration in phloem was shortened to less than 5 min in all imidacloprid treatments. The activity of mixed-function oxidase in aphids maintained on the treated seedlings with imidacloprid was elevated. In conclusion, imidacloprid could be used as a seed coating agent for aphid control, but chemical resistance in aphids should not be ignored.