The thesis is divided into two parts, the phylogeny of the Geothelphusa spp. from Taiwan and the adaptive strategy of Geothelphusa ancylophallu from the badland in the southwestern Taiwan. Through SEM studies, the male first gonopod (G1) microstructures of 22 species of Geothelphusa are compared. From the Numerical Analysis of 11 G1 measurements, it shows that Geothelphusa spp can be divided into the eastern and the western geographic groups in Taiwan. In addition, the main differences in G1 micro-morphology among Geothelphusa, including the rings of scales, the numbers of simple seta on the terminal segment, and the ratios of total length of G1 divided by the terminal segment length of G1. Twenty-seven species of Geothelphusa from type locality in Taiwan were compared via the sequences of mtDNA COI (658 bp). The results indicate that the ancestors of Geothelphusa landed onto the northwestern Taiwan about 3.74 mya. After that, Geothelphusa dispersed from northern Taiwan into the eastern and the western geographic groups, this result was consisted with the previous conclusion obtained by G1 SEM studies. The eastern geographic group was further dispersed to the northeast and evolved to the present-day Ilan Geothelphusa spp. Another subgroup distributed down south to the eastern mountains where are now Lishan area. The last subgroup reached more southern to the Hengtsuen peninsula, Lanyu, and Greenisland. The western geographic group was further dispersed down south and evolved to the present Geothelphusa olea and G. nanhsi which then evolved to G. caesia¡BG. wutai and G. tsayae. Another subgroup evolved to G. ancylophallus which then evolved to G. lili¡BG. shernshan¡BG. neipu and G. pingtung. The genetic structures of Geothelphusa in Kaoping River area were studied further via the sequences of mtDNA COI (658bp). The results indicate that G. tsayae have three main subgroups according to the river they live on (Nantsishan River, Laolong River, Eyeliou River). Among them, the Eyeliou-River subgroup has the sequences divergence of 1.2% to the G. wutai, with supporting rate of 73%-82%, indicating that they may belong to the same species. In addition, Laolong-River subgroup has the sequences divergence of 0.9% to the G. caesia group, with supporting rate of 60%, indicating that they may be the same species as well but more evidences are needed to clarify the situation. The adaptive strategy of the crabs Geothelphusa ancylophallu, distribute near the badland in the southwestern Taiwan, was studied. The strategies are as follows: 1) the breeding activity correlated to precipitation, mainly occurring in spring and summer, and the maximum in June. 2) The female crabs breed 32.5 offspring in average and the mean carapace width of the first stage crabs (C1) was 5.3mm. The C1 stayed with their mother for about 4 days. 3) G. ancylophallu finished building holes before the dry season and the holes could be used until the next wet season. The holes are used for drought-resistance and defending predators during the dry season and mating and breeding during the wet season. 4) G. ancylophallu could defense their holes. The residents spent 152.3 ¡Ó 110.1 seconds driving the invaders out of their holes and attacked them actively when near their holes. The residents¡¦ alert to sound from the ground. 5) Through the experiment of hole covering, 67.0% of the valid holes were used more than 4 months, with the longest of 13 months. The moving distance of G. ancylophallu at night was 146.8 ¡Ó 73.8 cm (n = 38). The G. ancylophallu are fidelity to their holes, especially in dry season.