GENERAL REFERENCES 



Banks, N. 1900. Synopses of North American Invertebrates — The Scorpions, 

 Solpugids and Pedipalpi. Amer. Nat., Vol. 34 



Comstock, J. H. 1940. (Revised and edited by W. J. Gertsch.) The Spider 

 Book. Doubleday, Doran and Co. New York. 



Ewing, H. E. 1928. The Scorpions of Western United States. Proc. U. S. 

 Nat. Museum, Vol. 73. 



KEY TO THE PRINCIPAL FAMILIES OF SPIDERS 



1. With the large basal segments of the chelicerae (first pair of mouth ap' 



pendages) projecting forwards and with the claws moving up and 

 down parallel to each other; with two pairs of book lungs; mostly in 

 the south — The Tarantulas 2. 



Basal segments of chelicerae usually projecting downwards and the claws 

 moving in the same plane or somewhat obliquely towards and away 

 from each other; only one pair of book lungs, except in one family 

 with extremely long and slender legs; widely distributed — ■ 

 The Spiders 5. 



2. Pedipalps (second pair of mouth appendages) each with a distinct en' 



dite (small lobe-like structure arising from the basal segment) 

 Atyp-idae Purse-web Spiders 

 Endites of pedipalps indistinct or wanting 3. 



3. With a rake on the chelicera (outer end of basal segment of chelicera 



armed with teeth) 



Ctenizidae Trap-door Spiders 

 No rake on the chelicera 4. 



4. Ends of legs with two claws and a bunch of hairs 



Theraphosidae Bird Spiders 

 (Aviculariinae) 

 Ends of legs v^'ith three claws and no bunch of hairs 

 Dipluridae Funnel-web Tarantulas 



5. With four respiratory openings (either with two pairs of lung spiracles 



or with one pair of lung spiracles and one pair of tracheal spiracles) 6. 



With three respiratory openings (with one pair of lung spiracles and a 



single tracheal spiracle) 10. 



I 6. With two pairs of book lungs; legs very long and slender; Tennessee 

 HypochxUdae Four-lunged Spiders 

 With one pair of lung spiracles and one pair of tracheal spiracles 7. 



7. With eight eyes grouped together on a low median knob towards the 



front of the cephalothorax; with cribellum and calamistrum present (ex- 

 cept in adult males) 



Filistaudae Filistatids 

 With six eyes; cribellum and calamistrum absent 8. 



8. Basal segments of all legs short and stout 



Oonopidae Oonopids 

 Basal segments of first two legs slender 9. 



209 



