INTRODUCTION. 



As an extensive knowledge of the structure and development of an 

 animal is indispensable for the understanding of the origin of its habits and 

 instincts and of its biological relation to the rest of Nature, so an exhausti\e 

 study of the species is imperative for a clear insight into the meaning of 

 geographical distribution, of intergrading and isolated faunas and of their 

 l)earing on the great problems of evolution. Complete treatises of local 

 faunas, such as have been published for many groups of animals of European 

 countries, are the ideal basis for further research. Unfortunately there is 

 no such treatise on spiders not only for the entire American Continent, but 

 even for the United States. The excellent little book of Emerton, Com- 

 mon Spiders, does not pretend to be such a treatise and being far from 

 complete is intended primarily to teach the beginner to recognize species 

 which do not offer difficulties of identification. Keyserling's great work 

 while remaining a standard of excellent descriptions and drawings of a 

 great quantity of spiders, has at present no faunistic value, since many 

 hundreds of species have been described after its publication. The two 

 wonderful volumes in the Biologia Centrali-Americana come perhaps 

 nearest to an ideal treatise of a local fauna, a treatise perfect in every respect, 

 but, as I mj^self had opportunity to control during my trip to the tropical 

 forests of the Mexican lowlands, fall far short of the immense wealth 

 of forms encountered in Central America. No other attempt has been 

 made to give a work comprising all known species of a local favma and the 

 growing number of recently described new species makes such a work 

 almost impossible. The difficulty is still further increased by the fact that 

 the bibliography of the subject is very extensive and that many papers 

 ha^•e been published in little accessible magazines. Many other species 

 have l)een described in papers dealing with spiders from various regions or 

 even continents. Again others have been published in bulletins of meetings 

 of different societies, have no title and have in consequence escaped notice 

 by the Zoological Record. The first help in such a condition is a synonymic 

 catalogue and monographs of special groups. Marx published twenty 

 years ago two catalogues, one of spiders of the United States, the other of 

 those of the District of Columbia. Both are even at present of great help 

 although considerably antiquated. Quite recently a catalogue was pub- 

 lished of the spiders of New England by Miss Bryant and one of Nearctie 

 Spiders by Mr. Banks. Of the monographs of special groups those of the 

 late F. Cambridge on tlie Cteniform spiders and on Latrodectus of the 



