234 



ANNELIDA AND ARTHROPODA: 



variable modifications of pedipaipi; nonpoisonous; 

 small to microscopic; larger species having a large, 

 toothed tongue are called ticks; smaller species with 

 a small untoothed tongue are called mites (Figure 

 14.9). 



Acarina are mostly minute, reddish creatures 

 whose bodies are unsegmented externally. They are 

 found in soil and stored foods, on plants and animals, 

 in fresh and salt water, and as plant and animal 

 parasites. Many live on a diet of plant and animal 

 juices. The bite of the Rocky Mountain spotted fever 

 tick often proves fatal to humans. The tick has no 

 poison glands but is host to a virus or bacterium 

 which is transmitted when the tick bites. This trans- 

 mitted organism is the cause of the disease. Redbugs 

 and chiggers are mites that attach to human skin, 

 causing violent itching. Some mites attack plants, 

 causing much economic damage. The free-living 

 Acarina are predators or scavengers; they tend to live 

 in debris or upon plants. 



sensory feelers; nonpoisonous, but some have stink 

 glands; size to about 5 inches (Figure 14.9). 



The whip scorpions are one of the scorpion-like 

 orders of arachnids, but the Pedipaipi difTer from all 

 similar creatures in the modification of their first pair 

 of walking legs into sensory structures. They do 

 resemble many of their relatives in that they inhabit 

 dry regions. 



Some whip scorpions are called vinegaroons be- 

 cause of the odor caused by the secretion from a 

 gland at the base of the tail. All are nonpoisonous 

 and mostly night predators which hide during the day 

 under objects, in crevices, or by burrowing in sand. 



ORDER PALPIGRADA (Micro Whip Scorpion$) 



Diagnosis: resemble whip scorpions, but pedipalps 

 are leg-like and eyes are lacking; minute in size, 

 under 1/10 inch, with half of length a slender tail 

 (Figure 14.9). 



ORDER SOLPUGIDA f= SOUFUGAE) (Sun Spiders or 

 Wind Scorpions) 



Diagnosis: Elongate and somewhat spider-like, 

 but abdomen consists of ten segments and is broadly 

 joined to cephalothorax; also lack spinning organs 

 and chelicerae with a terminal fang; chelicerae (not 

 pedipaipi) are modified into pincers; pedipelpi long 

 and leg-like, but are sensory and held forward like 

 antennae, or "feelers;" nonpoisonous; generally 1 to 

 2 inches long (Figure 14.9). 



The sun spiders sometimes are called wind scor- 

 pions, owing to their swift movements and general 

 appearance. These creatures are mostly night 

 hunters of warm, dry lands. Although they are not 

 poisonous and most are only 1 inch long, solpugids 

 have the largest pincers for their size of any arachnid. 

 It is amazing to see how effectively and rapidly a sun 

 spider can tear apart and suck the fluids of its prey. 

 The pincers are used with sawing motions, the sun 

 spider alternately holding fast with one and driving 

 deeper before holding with the other. 



ORDER PEDIPAIPI (Whip Scorpions) 



Diagnosis: scorpion-like, with abdomen of twelve 

 segments but not terminated by a stinger; end of 

 abdomen with or without a whip-like structure; 

 unique in having first pair of walking legs modified as 



ORDER ARANEAE(= ARANEIDA) (Spiders) 



Diagnosis: cephalothorax and abdomen narrowly 

 joined ("waist"), both unsegmented; chelicerae with 

 a poison duct in claw; posterior abdomen with silk- 

 spinning organs (spinnerets); poisonous; eggs com- 

 monly are protected in a cocoon (Figure 14.9). 



Spiders are among the main predators of any land 

 community, and they are very numerous. They 

 destroy more invertebrates than do birds. In some 

 places in the world they are used to control pests in 

 the home and elsewhere. Their silk is sometimes used 

 to stop human bleeding in rural Europe and America. 

 They are used as human food in some parts of the 

 world and are bird and fish food everywhere. 



Most possess enough poison to subdue prey. Poi- 

 son is injected by the fangs of the two chelicerae. 

 The vast majority of fangs are neither strong nor long 

 enough to penetrate human skin; moreover few spider 

 poisons are toxic to man. Contrary to popular belief, 

 the United States tarantulas are nonpoisonous. The 

 only possibly dangerous species in our country are 

 the black widow and, to a lesser extent, the gray 

 widow. Both produce a nerve poison, but neither are 

 likely to bite, even if handled. The black widow will 

 often cause grave illness, but its bite is rarely fatal. 



Spiders feed primarily on insects and other spiders. 

 Some American tarantulas, or bird spiders, are 

 known to have eaten small birds, mammals, fish, and 



