Arthropoda means "joint-footed" in Latin and describes arthropods' jointed bodies and legs connected to a chitinous exoskelelton.2 The majority of arthropods are benign to humans and environmentally beneficial. Some clinicians regard bites and stings as inconsequential and more of a nuisance than a threat to life. However, some spiders have toxic venoms that can produce dangerous, painful lesions or significant systemic effects. Important clinical syndromes are produced by bites or stings from animals in the phylum Arthropoda, specifically the classes Arachnida (spiders, scorpions, and ticks) and Insecta (bees, wasps, hornets, and ants) (Table 119–1). Infectious diseases transmitted by arthropods, such as the various encephalitides, Rocky Mountain spotted fever, human anaplasmosis, babesiosis, and Lyme disease, are not discussed in this chapter.
Table 119–1. Insects and Other Arthropods That Bite, Sting, or Nettle Humans |Favorite Table|Download (.pdf)
Table 119–1. Insects and Other Arthropods That Bite, Sting, or Nettle Humans
|Honeybee (Apis mellifera)||Hairy, yellowish brown with black markings|
|Bumblebee and carpenter bee (Bombus spp and Xylocopa spp)||Hairy, larger than honeybees and colored black and yellow|
|Vespids (yellow jackets, hornets, paper wasps)||Short-waisted, robust, black and yellow or white combination|
|Schecoids (thread-waisted wasps)||Threadlike waist|
|Nettling caterpillars (browntail, Io, hag, and buck moths, saddleback and puss caterpillars)||Caterpillar shaped |
|Southern fire ant (Solenopsis spp)||Ant shaped|
|Spiders (Arachnida) black widow, brown recluse||Body with 2 regions: cephalothorax, and abdomen; 8 legs|
|Scorpions (Centruroides)||Eight-legged, crablike, stinger at the tip of the abdomen; pedipalps (pincers) highly developed (not a true insect)|
|Centipedes (Chilopoda)||Elongated, wormlike, with many jointed segments and legs; 1 pair of poison fangs behind head|
Arthropoda comprises the largest phylum in the animal kingdom. At least 1.5 million species are identified, and half a million or more are yet to be classified. It includes more species than all other phyla combined (Fig. 119–1).2 Araneism or arachnidism results from the envenomation caused by a spider bite. "Bites" are different from "stings." Bites are defined as creating a wound using the oral pole with the intention for either catching or envenomating prey or blood feeding.84,185 "Stings" occur from a modified ovipositor at the aboral pole that is also able to function in egg laying as in bees and wasps. Stinging behavior typically is used for defense. Most spiders are venomous, and the venom weakens the prey, enabling the spider to secure, neutralize, and digest their prey. Spiders in general are not aggressive toward humans unless they are provoked. The chelicerae (mouthparts comprised of basal section and hinged fang) of many species are too short to penetrate human skin.
Taxonomy of the phylum Arthropoda.
Spiders can be divided into categories based on whether they pursue their prey ...