KEY TO PHYLA 



23 



2 (1) Molluscs with body always asymmetrical, frequently 

 spiral. Shell in one piece class gastropoda 



VTI. Phylum Arthropoda 



1 (44) Head provided with not more than a single pair of 



jointed appendages in addition to any feeler-like organs 

 which are attached immediately around the mouth open- 

 ing 2 



2 (3) Without distinctly jointed appendages on the thorax, 



often with non-jointed appendages. Entirely legless or with 

 abdominal prolegs. Head frequently reduced and retracted 

 within the pointed apex of the thorax 



CLASS INSECTA. ORDER DIPTERA (larvae) 



3. (2) Thorax 'bearing jointed legs.. 4 



4 (5) More than four pairs of legs class myriapoda 



5 (4) With two, three, or four pairs of legs 6 



6 (25) With one or two pairs of wings used in flight or at 



least capable of free movement. Immature insects having 

 immovable, rudimentary wings, enclosed in sacs or wing- 

 pads, are not included here, but under section 25. Usually 

 three pairs of legs, class insecta 7 



7 (10) Two pairs of wings, unlike in structure 8 



Fig. 3 



Back swimtner 



membranouB t\- 

 tlp 



Fig. 1 

 Giant water bug 



8 (9) Front wings leathery at base and membranous at 



Fig. 3 

 Water boatman 



Fig. 4 

 Water strider 



Fig. 5 

 Water scorpion 



