CHAPTER XIX 

 SCORPIONS, SPIDERS, MITES AND TICKS 



The scorpions, spiders, mites and ticks, composing the class 

 Arachnida of the branch Arthropoda, are popularly regarded as 

 insects but they differ from the insects in several important 

 respects. They have four pairs of legs instead of three pairs, 

 the body is not divided into three well defined regions, as it is 

 in most insects, but into two, and they have no antennae. 

 There are also important differences in the respiratory system 

 and other internal structures. 



The class is a large one including many diverse forms. 



Scorpions. The scorpions, order Arthrogastra, are found 

 chiefly in warm regions. They are usually nocturnal, hiding 

 away under stones or in crevices during the day, and coming 

 forth at night to capture their prey, which consists chiefly of 

 insects and spiders. These they seize and hold with their large 

 pincer-like maxillary palpi and sting with the poison fang at the 

 end of the long narrow part of the abdomen. The first seven 

 segments of the abdomen are broad and flattened, but the last 

 five segments are narrowed, more rounded and whip-like. The 

 last segment bears the poison-fang or sting, the poison from 

 which is quickly fatal to most small animals. Some species 

 are quite poisonous to man, but the kinds found in the United 

 States, while they may inflict a painful sting, are not usually 

 dangerous. 



Spiders. In the spiders, order Araneina, the abdomen and 

 the cephalothorax are very distinctly separated but the seg- 

 ments of each region are so closely fused as to be indistinguish- 

 able. The four pairs of legs vary in length according to the 

 habits of the different species; some are fitted for running, 

 others for jumping, others for walking over the ground or 

 grass or pver delicately spun webs. The pedipalpi, or feet- 



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