ARTHROPODA. 63 



Why do they come to the surface ? 

 e. Can they see ? (Test to find out.) 

 /. How rapidly do they grow ? (Observe for several 

 days.) 

 2. Under 1. or l.p. (Use mounted preparation.) 

 a. Identify a distinct head, thorax and abdomen. 

 h. The Head. Identify, — 



(1) the eyes; (Are they compound or single?) 



(2) the antennae ; 



(3) the vibratile organs; (These are short and 



bushy for sweeping microscopic food into 

 the mouth.) 



(4) the mouth. 



c. The Thorax. Ascertain whether there are to be 



seen, — • 



(1) any external legs ; 



(2) any legs folded up inside of the transparent 



body wall ; 



(3) any wings. 



d. The Abdomen. Make out, — 



(1) the number of somites ; 



(2) the respiratory tube, branching off near the 



end of the abdomen ; 



(3) the posterior opening of the alimentary 



canal. 



e. Draw a larva. 



C. Pupa. The third stage. 



1. Alive in a jar of water. 



a. How does the shape of the pupa differ from that 



of the larva ? 

 h. How does the position of the pupa in the water 



differ from that of the larva in water ? 



