20a (18b).    Tarsi with 4 segments; front and hind wings similar in size, shape and venation

                       (Figs.A-E)  cerci tiny or absent [termites]...............................................…........................Isoptera

 

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                            A                               B                                            C                                D                                 E                                                                                          

 

 

 

20b.    Tarsi with 3 or less segments; hind wings usually shorter than front wings; cerci either

            present or absent....................................................................................................…................…............ 21