Eleutherodactylus is a genus of frogs in the family Eleutherodactylidae. Many of the 200 species of the genus are commonly known as "rain frogs" or "robber frogs", due to their sharp, high-pitched, insect-like calls. The best-known species is the common coquí (E. coqui), which is both a national symbol of Puerto Rico and a notorious invasive species in Hawaii. Two Eleutherodactylus species, E. limbatus and E. iberia, are among the smallest known frogs, measuring only 8.5 mm in length (only slightly larger than Paedophryne amauensis, which measures around 7.7 mm). Etymology The name "Eleutherodactylus" is derived from the Greek words for ‘free-toed’, composed of the Ancient Greek (, ‘free, unbound’) and (, ‘finger, toe’). Most species are small, slender, and cryptically colored, with three to five free toes. A few, such as the web-footed coquí (E. karlschmidti) of Puerto Rico, do have completely webbed feet. Distribution and habitat Species of Eleutherodactylus are found throughout the Neotropics, including the southern United States, Mexico, Central America, and the Caribbean. Additionally, the common coquí (E. coqui) has been introduced to several islands in the Hawaiian archipelago, as well as elsewhere in the Pacific. They can be terrestrial, arboreal, or aquatic, typically living in forests or riparian areas, and feeding primarily upon arthropods. Many Eleutherodactylus species have highly restricted ranges and are found on only one island or in one or a few localities. Even some of these restricted species can occur at very high densities. Reproduction and development All species of Eleutherodactylus are characterized by direct development, in which eggs hatch directly into small frogs, completely bypassing the tadpole stage. This adaptation may be largely responsible for their ecological and evolutionary success. Most species are characterized by parental behaviors, such as egg-guarding by either the male or female parent. In some cases, even young froglets are attended by parents. Another extinct Puerto Rican species, the golden coquí (E. jasperi), gave birth to live young. Many species (for example, Cook's robber frog, E. cooki), also of Puerto Rico, exhibit sexual dimorphism in size and color. Study on Eleutherodactylus and Lithobates amphibians shows that number of offsprings instead of body size may help to find which species require conservation from being extinct. Phylogenetics The basis of forming this genus has been morphological, but sequence comparisons of protein-encoding DNA, mitochondrial DNA, and ribosomal RNA have shown geographic range is a much more consistent predictor of cladistics