During a visit to the Canary Islands in the early autumn of 1924, the chief purpose of which was an inspection of the banana plantations for insect and allied pests, four enemies were found, each of which was the cause of some loss. Two of these had relatively small importance, viz. a red spider (Tetranychus) and a thrips. The red spider was known locally as the “ red bug,” the popular name being “ aranillos ” (the little spiders) ; the mites were found on the fruits, which showed the paleness and discolouration that characterise plant tissue wounded by the red spider mouth-parts. The thrips, known locally as “ black bug,” also caused a paleness and discolouration of the attacked fruit. Both of these enemies were known to the Spanish workers as “ bicho blanco ” (the animal which causes a whiteness). The other two enemies were much more serious, one of them a moth, the banana miner, Hieroxestis subcervinella, Walk., the subject of another paper ; the second a scale-insect, Pseudococcus comstocki, the subject of this paper.