76 EVOLUTION IN COLOR-PATTERN OF THE LADY-BEETLES. 



MEASUREMENTS. 



The polygon (fig. 86) shows that the confluence of spots 5 and 6 does 

 not represent a well-marked center of variation. Fig. 87, which is intended 

 to test the same matter for the confluence of spots 2 and 3, fails, because 

 of the rarity of this variant, to show its true status. The decided skew- 

 ness in both polygons will be discussed in another connection. 



(a) 23 22 21 20 19 18 17 1015 M 13 12 11 10 9 87654321012345678 9 10 11 12 13 14 15 l(i 17 IS 19 '20 21 22 1", 



(6) 1 1 1 4 5 15121518272413 811C657532560211112021000010101 = 214 



(c) 003234 6 4 11 12 14 13 1-4 12 10 10 34C55C21020200 00100000100000000 = 1.56 



(d) 1 3 2 3 5 7 8 17*2727*2832393423111512111014*8*4 276221 1122021010010101 = 374 



FIG. 86. Variation of the distance between and confluence of spots 5 and C in Epilachna bvrealia at Cold 



Spring Harbor, New York. 



MODIFICATION. 



I was unable to modify the elytra by subjecting the prepupa and pupa 

 to changes of humidity and temperature. The pronotal pattern, how- 

 ever, is highly subject to modification by high temperatures. Fig. 85 gives 

 the range of the wild specimens. Individuals kept in an incubator at 40 

 C., and even those placed in the hot attic of the station buildings during 

 summer months, became very light in every case, as shown in fig. 88, and 

 closely approached the Texan species E. toweri. Some of the spots, 

 besides being smaller, have a lesser amount of pigment proportionately, 

 so that they were in some cases brownish rather than black. Prolonged 

 refrigeration, darkness, increase and decrease of humidity produce no 

 appreciable effects. Experiments with the high temperature referred to, 

 combined with high humidity, gave results similar to those with the high 

 temperature alone. Excessive heat was, therefore, the only agent to 

 produce modification and this was in the direction of reduced pronotal 

 pigmentation. 



The pupal coloration is subject to high pigmentation after a temperature 

 of 17 C. With the temperature at 40 C. the exuviae possess no pig- 

 ment, except in the spines. In the former case, the pigmentation was 

 generally associated with lines of greater frequency of spines. 



