Life History of Scaphiopus Holbrookii Holbrookii (Harlan). Part I: Larval Development and Behavior

With the purpose of working out the life history of Scaphiofiis holbrookii holbrookii (Harlan), a large colony of this interesting form has been studied in New Kent County, Virginia, since 1939. The study of growth and behavior of Scaphiopus from transformation to breeding is being continued and will be reported separately. The present report follows the development of Scaphiopus from egg to transformation. Since this study is based primarily upon field observations, the behavior of the tadpoles rather than their anatomical development is emphasized. The formation of schools is described, and a discussion of tadpole schooling in this and other species is presented. The embryology of S. h. holbrookii was not studied nor has it been reported in the literature. However, it probably is similar to that of S. bombifrons which has been described in detail in a series of papers, Trowbridge and Trowbridge ('37) ; Trowbridge ('41), ('42). The latter paper also presents a detailed account of the development of the tadpole to the completion of metamorphosis. The larval development of Scaphiopus h. holbrookii has been described by various authors, but most of these observations have been based upon specimens raised in aquaria. Wright ('32) reviewed the literature of S. h. holbrookii, and of the papers since that time, few have dealt with this phase of the life history. Ball ('36) describes tadpole behavior as observed in the field, and is the only author who has described aggregations of S. h. holbrookii tadpoles. Except where otherwise stated, the observations presented in this study were made in the field in 1940 and in 1944. In both of these years, a large colony of S. h. holbrookii, occupying approximately 300 acres, laid in a number of pools. In 1940, five pools were used as breeding sites, and in 1944, eight pools were used. These eight pools were all within a radius of three quarters of a mile, and afforded an unusual opportunity to follow the development of the tadpoles under natural conditions.