Natural products isolated from plants may be an alternative source of larvicidal and insecticide activity. Khellin is a natural furanochromone isolated from fruits of Ammi visnaga (L.) Lam. (Umbelliferae family), which grows extensively in the Mediterranean region. This substance shows several types of biological activity, such as in vitro cytotoxicity, antispasmodic action, and phototherapeutic potential. Dengue is a tropical disease caused by an arbovirus transmitted by Aedes aegypti; the milkweed bug, Oncopeltus fasciatus, is a phytophagous Hemiptera and a Phytomonas vector. Our main goal was to evaluate the toxicity of khellin in relation to the nymphs of O. fasciatus (Hemiptera) and larvae of A. aegypti (Diptera). To the best of our knowledge, this is the fi rst report concerning furanochromone bioactivity against insect vectors for human disease.