24 THOMAS SAY FOUNDATION 



peared to be vestiges of modally 3 in the fore wing and 2 

 in the hind wing with a range from 1 to 5. The costal 

 crossveins in the apical space, however, are strong. They 

 varied as follows : 



No. of crossveins 12 3 4 



Times occurring, fore wing 1 14 12 3 



Times occurring, hind wing 7 20 3 



The crossveins in the median space varied as follows : 



No. of crossveins -.2 3 4 5 



Times occurring, fore wing 2 12 9 7 



with none in the hind wing in this space. 



The crossveins in the intercubital space varied as fol- 

 lows : 



No. of crossveins 3 4 5 6 7 S 9 10 



Times occurring, fore wing ■"> 7 11 7 1 1 



Times occurring, hind wing 1 3 7 8 10 1 



Thus there is a wide range with the mode at 7 in both 

 wings. 



Crossveins between the anal veins of the fore wing be- 

 yond the anal cell are a distinctive mark of this genus. 

 They varied as follows : 



No. of crossveins 2 3 4 5 



Times occurring 4 12 9 5 



The m-cu crossvein is very variable in having a modal 

 length of about eight-tenths of that of the r-m crossvein 

 (infrequently longer), but often disappearing by fusion 

 of adjacent veins, the fused portion sometimes attaining 

 once or twice that length. 



The radial sector is normally 2-branched (a single fork) 

 but an extra twig at the tip of the anterior branch of the 

 fork occurred in three specimens and in three wings of 

 one specimen. The depth of the main fork varied from 

 origin at the cord to six-tenths the distance beyond the 

 cord, the mode being at three-tenths that distance. 



The branches of vein Cu pectinately arranged on the 

 anterior side (a character of this genus) vary in number 

 from 1 to 5, with the mode at three in the fore wing and 

 two in the hind; but six wings showed slight departures 

 from the typical pectinate arrangement of these branches. 



Variation in Acroneuria lycorias. — This was studied in 

 75 specimens, 25 males and 50 females, collected at one 

 time and place (Ithaca, N. Y., in June, 1905). The num- 

 ber of branches of radial sector was as follows : 



No. of branches 3 4 5 6 7 



Times occurring, fore wing 1 35 55 6 3 



Times occurring, hind wing 19 72 9 



