chap, in.] INSECTA. 77 



into wing covers, and the posterior often functional 

 in the males only. No true metamorphosis (Fig. 35). 



2. Neuroptera: dragon-flies, termites, With 

 two pairs of membranous wings. A true metamor- 

 phosis, or the life history consisting of three periods, 

 an active larval, a quiescent pupal, and an active 

 perfect or imaginal condition. 



With this group may be placed the Triclioptera 

 (caddis-flies). 



3. Coleoptera; beetles, cockchafers, lady-birds. 

 Anterior pairs of wings converted into wing-covers ; 

 these are distinctly horny. True metamorphosis. 



The parasitic Strepsiptera come nearest to this 

 order. 



4. The Hymenoptera (bees, ants) have the 

 mouth organs adapted for licking, as well as for 

 biting and cutting. Both pairs of wings functional. 

 Metamorphosis complete. 



. Haustellata. In this series the mouth 

 organs move from before backwards, or serve as 

 stabbing or sucking organs. 



5. Hemiptera (bugs, aphides, lice). Mouth- 

 organs stabbing and sucking. Anterior pair of wings 

 functionless ; in parasites both may be rudimentary. 

 Metamorphosis generally incomplete. 



6. Diptera (flies, fleas). Mouth organs stabbing 

 and sucking ; anterior wings functional, the posterior 

 possibly represented by the small knobbed " balancers " 

 (halteres). Metamorphosis complete. 



7. L-epidoptera (butterflies, moths). Mouth 

 organs form a sucking apparatus, with no power of 

 stabbing ; both pairs of wings functional. Metamor- 

 phosis complete. 



The Mollusca form a well-marked phylum, the 

 essential characters of which would be represented in 



