The biology of Vaejovis littoralis Williams, an intertidal scorpion from Baja California, Mexico

Vaejovis littoralis Williams is an intertidal scorpion inhabiting chiefly the drift zone in the high intertidal of beaches in Baja California, Mexico. Density within the drift zone averages approximately 2–4/m2 (island sites) to 12/m2 (mainland sites). Populations are aggregated into patches. Primarily, juveniles exhibit diurnal activity. Nocturnally active juveniles tend to be spatially segregated from nocturnally active adults within the drift zone. Diet of V. littoralis includes the isopod Ligia, V. littoralis, spiders, pseudoscorpions, centipedes and beetles. Prey size is not a function of predator size. Centruroides exilicauda, V. littoralis and Ligia were observed as predators on V. littoralis. The adult sex ratio is skewed toward females (1 male : 2.1 females). Adult females are usually larger than adult males. Litter size ranges from 1–8. Limited data suggest that offspring size and litter size increase with maternal size. Vaejovis littoralis exhibits cryptic coloration, small size and lithophilic tarsal claws, all of which favour intertidal existence. Although V. littoralis is able to withstand up to 12 hours of submergence, it does not survive submergence significantly better than a comparable desert species. Field data suggest that V. littoralis does not exhibit an endogenous tidal rhythm.