Identification. The Meloidae are narrow elongate beetles characterized by a “neck” (pronotum) which is distinctly narrower than its head or wings. Adult beetles range in body length from 1 to 2 cm (0.4-0.8 in) and vary considerably in their coloration. Distribution. In general, blister beetles are found in greater numbers in the western half of the United States.[5] Biology/Behavior. The immature stages of the blister beetle are usually predacious on other insects and are not harmful to man. Adult blister beetles release a clear amber fluid by rupture of thin membranes in the leg joints or other segmented areas of the body. The release of this fluid, which contains a vesicating agent called cantharidin, is triggered by pressure against the body of the beetle. Light pressure exerted by clothing or by brushing off a beetle is usually sufficient to cause the release of its vesicating fluid. The adult blister beetles are readily attracted to bright white light, and many cases of human exposure occur at night around such lights. Since the adults are plant feeders, some cases of human vesication occur as persons move through vegetation infested with blister beetles. Avoidance/Control. In areas with an abundance of blister beetles, use yellow light bulbs for outdoor lighting. If a meloid beetle lands on the skin, blow it off, do not crush it. Since cantharidin is distributed throughout the beetle’s body, crushing the beetle against exposed skin would result in maximum cantharidin exposure. Dermatoses resulting from blister beetle contact are seasonal, with the greatest number of vesicating incidents in the United States occurring in July, August, and September. Chemical control usually is not recommended because of the mobility and wide distribution of blister beetles. Envenomization Reaction/Treatment. This information is not included in the appendix because the envenomization reaction generally consists of a superficial linear bulla which does not require emergency treatment. 2. URTICATING CATERPILLARS a. IO MOTH CATERPILLAR (_Automeris io_) [Illustration: (unlabelled)] Identification. The _Automeris io_ caterpillar is the larva of the Io moth, which belongs to the moth family Saturniidae. A full-grown caterpillar is about 5 to 8 cm (2-3 in) long, pale green, with lateral strips of red or maroon over white running the length of the body. Near the center of each body segment is a partial row of tubercles armed with radiating green and black spines. Many of these spines are venomous, and their tips are connected to rather large individualized poison glands. Distribution. In the United States, the Io moth is found in the states east of the Rocky Mountains.[68]