STUDIES OF VARIATION IN INSECTS 253 



than the variation in actual size of the wing. If one of these 

 kinds of variation may be looked on as in part acquired, /. e., 

 dependent directly on the nutrition or generally favorable or un- 

 favorable circumstances during development of the individuals, 

 it is the variation in size ; the variation in character of the wing 

 venation can certainly not be looked on as directl}' responsive 

 to any external influence tending to modify in any particular 

 way the course of the veins, structures which do not undertake 

 the performance of their function at any time during immature 

 life. But it is interesting to note that precisely this strictly 

 blastogenic variation is markedly greater than that variation (in 

 size) which might be considered to be in some part at least im- 

 posed on the individual during development. 



The bilateral correlation in these dimensional wing variations 

 seems, so far as indicated by the coefficients for right and left 

 wings, to be close. 



Variation in the Venation of Mosquitoes (Grabhamia curriei and 

 Culex incidens). — A lot of live pupae of the western salt-marsh 

 mosquito, Grabhamia curriei\ were collected from a small, shal- 

 low brackish water puddle (3 feet by 5 feet by 4 inches deep) 

 near an inlet on the salt marshes of San Francisco Bay, near 

 Stanford University. These pupas were brought into the labora- 

 tory in some of the water from the puddle, and the adults, which 

 emerged in two and three days, were killed immediately. The 

 wings of 50 males and 50 females were removed, mounted on 

 glass slides, and their size and venation studied for variation. 

 All measurements were made under magnification with an ocu- 

 lar micrometer. Mosquitoes are insects with complete meta- 

 morphosis, and the wings of the adults (imagines) appear in 

 their full size and of definitive venational character immediately 

 on their appearance (after expansion and drying). 



The range of length of wings of the males was from 3.7 mm. 

 to 4.3 mm., the mode 4.03 mm., the mean 4 mm., the standard 

 deviation 1.15 mm. and the coefficient of variability 2.85 +. 

 In the females the range is 3.4 mm. to 4.02 mm., the mode 

 3.8 + mm., the mean, 3.8 mm., the standard deviation 1.05 

 mm. and the coefficient of variability 2.76 +. Thus in size of 

 the wing, the males (averaging a little larger actually) show a 

 Proc. Wash. Acad. Sci , Dec, 1904. 



