The representatives of the genus Hylesia Hübner, [1820] are significant among the medically important Lepidoptera. Adult females use abdominal setae to wrap and protect the eggs that remain for months in nature. These setae, in contact with human skin, may cause allergic reactions including swelling, itching and local erythema, known as lepidopterism. The morphology of the abdominal scales and setae from the female H. oratex Dyar, 1913 is herein described and aspects related to their medical significance are discussed. Portions of each abdominal segment were examined through a scanning electron microscope. Two types of scales without medical importance, and two types of setae with medical importance, classified as "true setae" and "modified setae" were found. The true setae, which are slightly fusiform and have radially arranged lateral projections, are responsible for the allergic reactions caused by skin penetration. The modified setae, which are larger, curved, with the median enlarged and serrated margins, can be responsible for the release of chemical substances. This information provides a better understanding of the structure of the urticating setae, which are responsible for lepidopterism outbreaks in humans, and contributes towards the identification of the moth species involved.
allergic outbreaks; lepidopterism; morphology; urticating moths
