Tegrodera aloga, commonly known as the iron cross blister beetle, is a species of blister beetle in the family Meloidae. It was first described by Skinner in 1903.
Distribution and Habitat
The species is found in the southwestern United States (Arizona and California) and in Sonora, Mexico. It is endemic to the Sonoran Desert region.
Description
Tegrodera aloga is approximately 2 cm (0.8 in) in length, with a long, narrow, cylindrical body and a wide head. The beetle is black with contrasting yellow and red spots. The common name refers to a black cross-shaped pattern on the wing covers (elytra). Its bright coloration is a form of aposematism — a warning signal to predators indicating the presence of toxic chemicals.
Toxicity and Cantharidin
The beetle secretes cantharidin (C₁₀H₁₂O₄), a potent chemical toxin, through its leg joints and antennal pores as a defense mechanism. Contact with the substance causes severe skin blisters (dermatosis) within hours. Cantharidin is poisonous if ingested, with a lethal dose of approximately 10 mg (or 0.5 mg/kg of body weight) in humans. In horses, the lethal dose is 1 mg/kg. The beetles pose a particular concern for livestock when they are inadvertently killed during alfalfa harvest and incorporated into baled hay.
Behavior and Ecology
Males compete among themselves for mating opportunities. Mating occurs with the male riding on the female's back as they move among flowers and leaves. Adults feed on spring blossoms of Nama hispida, Eriastrum, alfalfa, and other desert plants, and also drink nectar. The hosts of the parasitic larvae are unknown but are presumed to be ground-nesting bees.
Relationship with Humans
Despite its toxicity, cantharidin has medical applications. It has been used as a topical medication for the removal of warts and tattoos, and has been investigated for potential use in certain cancer treatments.
