CHAPTER VII 



The Tarantulas 



TH 



HE NAMES OF TARANTULA, TRAP- 



door spider, purse-web spider, and liphistiid bring to mind some of 

 the most famous of all spiders spiders that rival in size the largest 

 land invertebrates, spiders that have become renowned for their 

 wonderful burrows and handiwork. All are four-lunged spiders 

 belonging to the suborder Mygalomorphae; they are often referred 

 to as mygales but in this book are collectively known as "taran- 

 tulas" or mygalomorph spiders in contrast to the "true spiders" of 

 the suborder Araneomorphae. 



The mygalomorph spiders are more generalized than the true 

 spiders and ancestral to them. As a group they are longevous, all 

 living more than a single year and some of them attaining great 

 age as age is measured in invertebrates: up to or even exceeding 

 twenty-five years. They are large, probably averaging more than 

 an inch in length as compared with less than one-fourth that size 

 for the true spiders. Some of the typical tarantulas attain a body 

 length of three and one-half inches; at the other end of the scale, 

 the pygmies, the tunnel and sheet weavers of the genus Micro- 

 hexura, are one-eighth inch long. Along with great size the myg- 

 alomorphs perhaps retain as a consequence the second pair of book 

 lungs and other generalized features correlated with their primitive 

 station among spiders as a whole. 



Although it must be conceded that the true spiders have attained 

 a higher degree of development as evidenced by their greater 

 numbers, variety of structure, and multiplicity of habit the taran- 

 tulas should not be thought of as vastly inferior. They have become 

 notably specialized in their own way, and in instinctive behavior 

 have nearly kept pace with their cousins. 



The most important single character that distinguishes the myg- 

 alomorph spiders is the articulation of their chelicerae termed 



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