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The phylum Arthropoda is the largest division of the animal kingdom. The phylum includes insects (bees, wasps, hornets, flies, mosquitoes, bedbugs, fire ants, caterpillars, fleas), arachnids (spiders, scorpions, chiggers, ticks), and crustaceans (shrimp, lobsters, crabs). Venomous bites and stings from arthropods are a significant worldwide problem.1 In the U.S., the American Association of Poison Control Centers reported almost 50,000 cases of exposures to arthropods in 2008.2 Some of these were listed as resulting in major or severe reactions, including severe pain, neurotoxicity, or other signs and symptoms. Fatalities among these exposures are rarely reported to poison centers and usually result from allergic reactions to Hymenoptera stings. Clearly, these numbers are the tip of the iceberg. Toxic reactions to multiple stings by members of the order Hymenoptera and severe systemic allergic reactions to one or more stings or bites of other insects, such as deerflies, blackflies, horseflies, and kissing bugs, can all present as emergency, life-threatening situations (Table 205-1).3 Other arthropod bites and envenomations merit review either because they cause specific organ system toxicity or because they can result in transmission of infectious disease. This chapter discusses the more common and serious arthropod bites and envenomations encountered by emergency physicians.

Table 205-1 Harmful Arthropods of the U.S.

The Hymenoptera are the most important venomous insects known to humans, and more fatalities result from stings by these insects than by stings or bites by any other arthropod. There are three major subgroups or superfamilies of medical importance: (1) Apidae, which includes the honeybee and bumblebee; (2) Vespidae, which includes yellow jackets, hornets, and wasps; and (3) Formicidae, or ants (Figure 205-1).

Figure 205-1.

Representative venomous Hymenoptera. A. Hornet (Vespula maculata). B. Wasp (Chlorion ichneumerea). C. Yellow jacket (Vespula maculiforma). D. Honeybee (Apis mellifera). E. Fire ant (Solenopsis invicta). (Reproduced with permission from Merck, Sharp & Dohme, Division of Merck & Co., Inc.)

Bees and Wasps (Apidae and Vespidae)

Apids, such as honeybees and bumblebees, are usually ...

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