78 



VARIATION IN LEPTINOTARSA. 



Variation in the color pattern of the group proceeds in two directions, one 

 antero-posterior, the other from right to left, and between these there are no 

 intermediate conditions. All variations are restricted definitely in position 

 by controlling forces which we shall study later. In these two directions 

 variations of fluctuating character following Quetelet's law r abound. 



Quantitative study of the variations of the elytra in the lineata group. The 

 quantitative study of these variations has been made by seriations into classes. 

 We shall examine first, the frequency of certain types of variation, and, sec- 

 ond, the proportion of light to dark in the color of the elytra. 



Table 23. Frequency of variation in the elytra in L. undecimlineata, L. multitaniata, 

 L. dccemlineata, and L. juncta, expressed in percentages. 



Classes of variations. 



L. undecim- 

 lineata. 



No fusions 



co. + (cu. -f- a.) p 



(sc. a. + sc. p.)p 



(sc. a. -\- sc. p.) a 



{sc. a. + sc. p. ) a. to p 



(ra. + sc. p.) a 



{ra. + sc. p. ) p 



(m. + ra.) a 



(m. + ra.) p 



(All fused) a 



(All fused \p 



Transverse fusions between sc. a 



and sc. p 



Transfusions sc. p. and ra 



Transfusions ra. and m 



Stripes absent : 



c. 



sc. a 



sc. p 



ra 



m 



c. 



a 



12. 



20. 

 40. 



45- 



8. 



10. 



12. 



15- 



11. 

 o. 

 o. 



0.5 



0.01 

 0.02 



L. multitce- 

 niata. 



II . 

 12. 

 80. 



3- 

 I . 



4- 

 29. 



18. 



3- 

 6. 



i-3 

 0.1 



0.09 



o. 

 o. 

 o. 

 o. 

 o. 

 o. 

 0.2 



L. decern- 

 lineata. 



31- 

 3- 



65- 

 '9' 



o. 1 



24- 



2. 

 18. 

 70. 



5- 



1.5 



2. 



14 



1.1 



05 



o. 



o. 



o. 



0.2 



1.6 



4- 



L. juncta. 



5- 



95 

 76. 



1. 



o. 



o 



o. 



o. 



o. 



78. 

 o. 

 o. 



IOO. 



o. 

 o. 

 o. 



2. 

 18. 

 98. 



The frequency with which certain types of fluctuating variations occur 

 is of interest, especially when we consider them with reference to the possi- 

 bility of their being of use in the production of new species or modifica- 

 tions. In table 23 the variations are designated by classes and formulae 

 similar to those used in the discussion of variation in the pronotum. In 

 these formulae c. = costal stripe; sc. subcostal stripe ; r. = ramous; cu. = 

 cubital ; m. = median ; a. = anal ; sc. a. = anterior subcostal ; and sc.p. = 

 posterior subcostal. Fusions are indicated by +, and the absence of a 

 stripe by the abbreviation for it followed by minus in parentheses ( ). 



a 

 (Sc. a. + sc. p.) p. and (sc. a. + sc. p.) a. indicate that the two subcostal stripes 

 P 



