This is a Master's Thesis that describes the ecology and ecophysiology of the supralittoral amphipod (beach hopper) Traskorchestia traskiana, including its life cycle, resistance to desiccation, and salinity tolerance. The species inhabits algal drift banks in the upper beach zone, where it is often the most abundant detritivore. It reproduces in the spring and in the fall, with the spring reproductive peak generating the greatest number of offspring. The spring reproductive peak is mostly the result of the reproductive activity of older, larger females that have over-wintered from the previous year, while the smaller fall repoructive peak is due to the reproductive activity of younger, smaller females born during the previous spring. T. traskiana is highly vulnerable to desiccation but tolerates a wide range of salinity. It is a hypo/hyper-osmotic regulator, which allows it to survive the wide salinity fluctuations characteristic of most supralittoral zone habitats. But its low resistance to desiccation means that it can only survive in microenvironments characterized by a high moisture content and/or near-saturation relative humidities. The author supports these claims with field observations and with data obtained through field and laboratory experiments.