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.

Three species are described in the genus Loxoblemmus (Orthoptera: Gryllidae) in the Repulbic of Korea: L. campester, L. equester, and L. doenitzi. Although males of L. doenitzi are characterized by triangluar-shaped horns on the face, these three species are generally difficult to distinguish based on morphological characteristics. Here, we compared males of L. doenitzi and L. campester collected from Mokpo and Jeju Island, using morphological, calling song, and DNA sequences data. In the tegminal characters that may be responsible for calling song production, harp and mirror areas were significantly different between L. doenitzi and L. campester, whereas there was no significant difference in the number of files. In the calling song characters, pulse number per chirp and peak amplitude were significantly different between L. doenitzi and L. campester, whereas pulse duration, pulse period, chirp period, and phrase period were not. The phylogenic tree analysis based on 16s ribosomal RNA gene sequence, the genetic distance between L. doenitzi and L. campester was very close (0.1-0.15), suggesting that these two species recently diverged from the common ancestor.