STUDIES OF VARIATION IN '' INSECTS 271 



spend the winter in this curious gregarious manner. With 

 spring they will separate, scattering from the safe mountain 

 haunt to the open orchards and fields and gardens of the nearby 

 valley to lay their eggs and then die. The struggle for exist- 

 ence may be severe among the lady-birds ; they are surely 

 abundant enough and specialized enough in their food habits to 

 lead one to expect it to be unusually sharp ; but it is not sharp 

 enough to make the presence or absence of any particular one 

 or two or half a dozen or dozen or score of black spots on 

 the back a necessary condition to successful life. As far as 

 these observations of the habits and variation status of Hiffo- 

 damia convergens have any worth as a recorded test of the rigor 

 of natural selection they certainly point to a degree of that rigor 

 considerably lest than that commonly held and expressed by 

 thorough-going disciples of the Allmacht of the natural selec- 

 tion factor in evolution. 



It is obvious, of course, that if we could examine a large series 

 of Hippodamia individuals in adult condition, but before expo- 

 sure to the struggle for existence (in this condition), that we 

 should be able to speak more confidently of the exact relation 

 between the color pattern and its life and death selective value 

 to individuals. If no greater (and it is practically beyond pos- 

 sibility for there to be any greater) variation were found to exist 

 among a series of 1,700 individuals with definitive adult pattern 

 taken before exposure to the struggle for life than in a series of 

 1,700 after such exposure we could say definitively that a varia- 

 tion ranging from none to 18 black spots on the red-brown 

 elytra of this insect (these none to 18 spots being composed of 

 a great many different possible combinations, subtractions from 

 and additions to 12 spots arranged in a certain way, the modal 

 number and arrangement), has no absolute life and death selec- 

 tive value to the individuals and therefore could not offer any 

 " handle" for natural selection. We are trying so far with- 

 out success to obtain a large series of pupae of ffippodamia 

 from which to rear adults unexposed to the struggle for 

 existence. 



Variations in Pattern of Pronotum. The 536 individuals 

 composing the modal subclass i of class A, of the series of 1,031 



