170 



THE WING-VENATION Of LEt>IDOtTEKA, 



near the base of the former, the small basal portion of M^, left 

 uncaptured, tends to become straightened out into line with the 

 ascending base of Cuia. Thus there becomes formed a strong 

 three-pronged fork, the irigamma, which forms the posterior 

 closure of the Lepidopterous cell. The prongs of the trigamma 

 are, from above downwards, M3, Cuja + M^, and Cunj respectively; 

 and the method of its formation is indicated in Text-fi2:.3. 



Text-tiir.4.'' 



Text-liir.o.t 



The trigamma is the key which unlocks the homologies of all 

 Lepidopterous wing-venational types. In Text-figs. 4-6, the 

 author has applied it to Zeuzera^ Castjiia, and a butterfly, 

 [Euplxea) representing three important and outstanding types of 

 venation. In Text-fig. 7, the author has taken Hampson's 

 "typical moth-venation " (p. 31 8 in Sharp's Insects, Vol. ii.), and, 

 by slight alterations, has transformed it into a "typical moth- 



"" Wing-venation of Zeuzera (VurriJhi H.-Sch. In the forewing, R2-f 3 is 

 quite fused with Rj above dc, so that R., appears to be a second radial 

 sector arising from Rj . Notice the difierence in venation of fore- and 

 hindwings (heteroneurism). 



t Wing-venation of Castnia sp., (from .Sharp). Notice the presence of 

 the archaic Cuo in forewing, also the incomplete formation of M at mf. 

 x\n example of heteroneuric venation. 



