URTICATING/VESICATING ARTHROPODS
1. BLISTER BEETLES
(Order: Coleoptera; Family: Meloidae)
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)
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]
Biology/Behavior. Io moth larvae feed on the leaves of a variety of plants, including corn and willow.[17] In most areas they produce only one annual generation, emerging as a moth in the spring or summer and overwintering as a pupa. In south Texas, however, two generations occur, with one developing in May-July and the second in October-December. Therefore, the urticating larval stages can be found anytime from early spring to late fall, depending upon the area of the country and climatic conditions. As with most urticating caterpillars, A. io envenomizations normally occur when the victim inadvertently contacts caterpillar-infested vegetation. At the instant the victim’s skin touches this caterpillar, the spine tips break off in the skin, thus allowing toxin to flow out of the hollow spines and onto the skin.
Avoidance/Control. Wear gloves, a long-sleeved shirt, and long pants when working in an infested area. Children should be warned not to handle caterpillars. If necessary, infested vegetation may be treated with an appropriate insecticide.
Envenomization Reaction/Treatment. (See [appendix].)
b. PUSS CATERPILLAR
(Megalopyge opercularis)
Identification. The puss caterpillar is the larva of a lepidopterous group commonly referred to as “flannel moths.” In some parts of the United States the larva is incorrectly referred to as an “asp.” When fully mature, the larvae are near white to dark gray in color, 2 to 3 cm (0.8-1.2 in) long, and completely covered dorsolaterally with hairs that cause them to resemble elongate tufts of cotton. Some of the hairs are venomous, and when they penetrate the skin a “toxin” passes from an underlying gland through the hairs at the points of contact. The color variation of the larvae in this species is dependent upon larval age, locality, and time of year. In Texas, where this species is most abundant, the spring/summer generation of caterpillars is usually lighter in color than the fall generation.
Distribution. This species has been recorded primarily from the Southeastern States, including Alabama, Arkansas, Florida, Georgia, Louisiana, Maryland, Mississippi, Missouri, North Carolina, South Carolina, Texas, and Virginia.
Biology/Behavior. In most of the southern area of its range, the puss caterpillar is thought to have two generations per year. The first generation develops in the spring and early summer, while the second generation develops in the fall. After emerging from a cocoon and mating, the female moth lays her eggs on a suitable host plant. In a few days the eggs hatch into larvae, which develop by feeding on the leaves of a wide range of trees and shrubs. The natural enemies of the puss caterpillar usually keep its numbers under control; however, every 4 or 5 years the caterpillars become more numerous, and the number of envenomizations associated with them increases.[66]
Avoidance/Control. Always wear protective clothing such as gloves and a long-sleeved shirt when working in areas heavily infested with puss caterpillars. During periods of M. opercularis abundance, children should be instructed to stay away from infested trees and shrubs and not to handle caterpillars. If necessary, heavy puss caterpillar infestations may be treated with an appropriate insecticide.
Envenomization Reaction/Treatment. (See [appendix].)
c. SADDLEBACK CATERPILLAR
(Sibine stimulea)
Identification. The saddleback caterpillar is easy to recognize since its brown sluglike body is covered mid-dorsally with markings that resemble a brown or purplish saddle sitting on a green and white saddle blanket. Upon close examination, stout spines can be observed along the caterpillar’s lateral body margin and on its four tubercles. Many of these spines are hairs that are connected at their bases with individual poison glands. Just prior to pupation and subsequent development into a moth, the caterpillar is 2-3 cm (0.8-1.2 in) long.
Distribution. In general, the saddleback caterpillar in the United States is distributed southeast of a diagonal line drawn from Massachusetts through the middle of Texas.[68]
Biology/Behavior. From May to November, Sibine stimulea caterpillars may be found feeding on the leaves of a large variety of trees, shrubs, and other plants. Envenomization usually occurs when the victim accidentally contacts vegetation infested with these caterpillars. At the instant the victim’s skin contacts the caterpillar, the spine tips break off, thus allowing toxin to flow out of the hollow spines and into or onto the skin.
Avoidance/Control. When working in infested areas, wear gloves, a long-sleeved shirt, and long pants to prevent accidental envenomization. During periods of local heavy infestations, children should be instructed to avoid trees, shrubs, and other vegetation commonly infested with these caterpillars. Local entomologists may be contacted to obtain information on the most effective insecticide for saddleback caterpillar control in a given area.
Envenomization Reaction/Treatment. (See [appendix].)