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