ARTHROPODA. 267 



Shell not bivalved, but folded and much larger than 

 transparent body; swim by two large branched antennae; 



Daphnia (Phyllopoda) . 

 No shell; body segmented. 



Long, slender body; n pairs of leaf- like swimming feet, 



Branchippus (Fairy-shrimp) . 



(Phyllopoda) . 



Short, pear-shaped body ; two brood pouches at base of 

 abdomen ; 4 or 5 pairs of appendages, 



Cyclops (Copepoda). 



280. Key to the Chief Orders of Arachnida. 



Parasitic forms with rounded bodies; minute; segmentation 



poorly shown Order i, Acarina (mites, etc.). 



Boophilus (cattle-tick) . 

 Sarcoptes (itch-mite). 

 Free forms. 



Long, jointed abdomen Order 2, Scorpionida. 



Buthus (scorpion). 

 Soft, short, unjointed abdomen. 



Very long slender legs Order 3, Phalangida. 



Liobunum (harvest-men) . 



Legs of moderate length; poison glands . .Order 4, Araneida 



(true spiders). 

 Do not spin web to catch prey (wandering), 



Running spiders (Lycosa). 

 Jumping spiders (Attus). 

 Spin a definite web (sedentary). 



Tunnel in ground; line it with web, 



Trap-door spiders (tarantula). 

 Make tube of cobweb in the grass, 



Tube- weavers (Agalena) . 



Spin irregular cobweb Net -weavers (Theridium). 



Spin regular, geometric webs Orb- weavers. 



(Argiope; Epeira, etc.) 



281. Key to the More Important Orders of Insects. 

 Mouth parts suited for biting and chewing. 



w - / Spring tail, and allies. 



' \ Degenerate members of other orders. 

 With two pairs of wings. 

 Wings unlike in structure. 



Anterior wings somewhat thicker; posterior folding fan- 

 wise beneath them . . Order Orthoptera. 



