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ORDER HEMIPTERA 



by an organ located in the base of the abdomen, covered 

 by the wings when folded and slightly covered from below 

 by an operculum. The structure of the drum is somewhat 

 flattened and inside is a cluster of muscles attached to the 



j4. — Tibiccn scplcndeccin: adults oN'ipositiiit 

 (Photo from Ohio Exp. Sta.) 



abdominal wall. Their contraction serves to draw this 

 membrane in, after which it immediately resumes its former 

 position and when repeated rapidly this causes a vibration, 

 producing a whirring or buzzing note which varies in inten- 

 sity with the rapidity of the vibrations. Its purpose has 



