Aphids feed on host plants by penetrating the stems or leaves with stylets. The feeding behavior of aphids consists of probing, penetration, salivation, and sap ingestion. To assess the effects of sound on feeding behavior, we monitored the stylet activity of the green peach aphid, Myzus persicae (Sulzer), using electrical penetration graph (EPG). The use of EPG was critical for determining the stage, frequency, and duration of feeding in aphids. We played back three acoustic stimuli of sine waves with frequencies of 100, 1000, and 5000 Hz to adult aphids. In the sound treatment group, the frequencies of probing, penetration, and salivation increased, whereas the duration of sap ingestion decreased. The results of EPG revealed that the acoustic stimuli may restrict aphid feeding by inhibiting sap ingestion.

To understand the evolution and speciation of closely related species, a multiple approach encompassing morphological, behavioral, and genetic analyses is necessary. In Korea, three species of Loxoblemmus crickets occur widely. L. campestris and L. equestris are morphologically indistinguishable, whereas males of L. doenitzi are different from the other two species in head morphology. The genetic analyses using the partial mitochondrial COI sequences showed that L. doenitzi diverged off earlier than L. campestris and L. equestris. The analyses of laboratory recordings revealed that distributions of calling song characters generally overlapped among three cricket species. However, the number of pulses in a chirp was two in L. doenitzi and four in L. campestris, but it was greater than or equal to six in L. equestris. Provided that females make mate choice based on this calling song character, the differentiation in this character may lead to premating reproductive isolation and may have evolved during the speciation proccess in these closely related species.