The ant-loving crickets (Orthoptera: Myrmecophilidae) are obligate inquilines within ant colonies that obtain nourishment from ants in their nests. Recently, new morphological and genetic approaches have revealed more ant cricket species than had previously been recognized and have provided insights into their host specificity. In this study, we compare the degree of host specificity and behavior between 2 cryptic lineages of the ant cricket Myrmecophilus kubotai Maruyama that distinctly differ in their mtDNA sequences but are morphologically indistinguishable. In the field, crickets of lineage I (specialists) were found in nests of Tetramorium tsushimae Emery (Myrmicinae) at a high frequency (89%); whereas, crickets of lineage II (generalists) were found in nests of up to 12 ant species belonging to Formicinae and Myrmicinae. Behavioral observations in ant nests revealed that lineage I suffers few ant attacks and showed frequent intimate behavior with ants, i.e., grooming. In contrast, lineage II often suffers ant attacks and showed less frequent host grooming. In Japan's Nansei Islands, a “super-specialist” species of ant cricket that lives commensally with a single ant species has been reported to depend on mouth-to-mouth feeding from the worker ants; whereas, another “super-generalist” species that lives commensally with a variety of ant taxa feeds itself. Compared with these, the 2 lineages in the present study exhibited intermediate host specificity and behavioral specialization. These results suggest that there are various stages of specialization of commensalism in this genus.