For many years the presence of the tropical cattle tick, Boophilus annulatus microplus (Can.) (australis Fuller), in Puerto Rico has been a serious impediment to the development of the cattle industry in that island. In addition to heavy losses occasioned by tick infestation alone, the role of these ectoparasites in the transmission of tick fever of cattle has resulted in enormous losses and has presented an obstacle to the introduction of the better breeds of non-immune stock from tick-free areas.Resumen en español