ORGANIC EVOLUTION 



229 



Study JO. Determination of homologies of wing veins in 

 three series of closely allied insects. 



Materials needed: Enlarged prints of the wings figured 

 herewith (or of any other series, showing like phenomena), 

 and a single mounted wing of the common cranefly, Tipula, 

 with which to begin. 



8 



10 



II 



Fig. 141. Venation of the wings of a series of Psocids. /, Thyrsopsocus; 2, 

 Dictyopsocus; j, Taeniostigma; 4, Epipsocus; j, Ptilopsocus; 6, Myopsocus; 7, 

 Psocus;<S, Peripsocus; g, Polypsocus; /o, Calopsocus; //, Ca;cilius. 



