256 KELLOGG AND BELL 



acter, which may be partly acquired, but varies about twice as 

 much as this character. 



To test this independence of variation in size and venational 

 character in specific cases, the relation of the size to the mean 

 and mode of size, and the relation of the measurement of the 

 vein in relation to the mean and mode of this character ma}' be 

 noted for several individuals. 



In the males the modal length of wing is 4.03 mm. and the 

 mean 4 mm. ; the modal length of the measured vein 1.15 mm. 

 and the mean almost exactly the same, yet one male with wing 

 4.15 mm. long has the vein only i mm. long; another with 

 wing 4.17 mm. long has the vein 1.13 mm. long; another with 

 wing 4.21 long has the vein 1. 16 long (wing lengths above mode 

 and vein lengths below or at mode); two with wing 3.9 mm. 

 long have vein 1.16 mm. long, another with wing 3.9 long has 

 vein 1. 3 1 long (wing lengths below mode and vein lengths 

 above or at mode). In the females the modal length of wing is 

 3.8 mm. the mean the same, the modal length of vein 1.02 mm. 

 the mean 1.03, yet several individuals have wing length of 3.9 

 mm. and a vein length of .98 mm. while one has a wing length 

 of 3.85 mm. and a vein length of .87 mm. (wing lengths above 

 mode and vein lengths below mode) ; and several have the wing 

 3.7 mm. long and the vein 1.05 mm. long while one with wing 

 only 3.38 mm. long has the vein 1.14 mm. long (wing lengths 

 below mode and vein lengths above mode). The variation in 

 venation is manifestly not a simple function of the variation in 

 size of wing in this lot of mosquitoes. 



In a lot of adult mosquitoes, Ciilcx incidcns, emerged in the 

 laboratory from larvae and pupa^ collected at one time (Septem- 

 ber 16, 1901) from a watering trough, the variation in size 

 (length) of wings and in length of third longitudinal vein (same 

 as in case of the salt marsh mosquitoes referred to above) were 

 studied in 30 males and 30 females. 



In the males the length of third longitudinal vein ranges 

 from .95 mm. to 1.2 mm. the mode being 1.03 mm. the mean 

 1.07, the standard deviation .61^ mm. and the coefficient of varia- 

 tion 5.86. 



In the females the length of the vein ranges from 1.02 to 1.27, 



