98 THE NEXT GENERATION 



He could tell by the looks of any beetle whether she was 

 about to lay her eggs or whether she had already done so. 

 Accordingly, in 1902, just before egg-laying time came, he 

 chose six pairs of beetles, put them into a very warm, damp 

 breeding place, and kept them there until they had laid 492 

 eggs. He called this set Lot A. He next put both the beetles 

 and the eggs in normal conditions again. Here the beetles 

 laid the rest of their eggs. There were 509 of them. They 

 were labeled Lot B. The larvae of both sets grew up together. 

 As it happened, many of the eggs in both Lot A and Lot B 

 did not hatch. Many larvae did not live. But we may im- 

 agine how carefully Dr. Tower watched those that did live 

 to become ancestors. 1 And he had his reward. 



He tells us that the parents of these particular beetles 

 were of the species Leptinotarsa multitaenita, and that they 

 had been brought from Mexico. Now it seems that when 

 beetles of this species are frightened, they " feign death," as 

 it is called, by falling to the ground with their legs folded 

 close, up against the body, and they lie there motionless until 

 they consider it safe to unfold and be alive again. 



But there is still another species of these same beetles in 

 Mexico, called Leptinotarsa melanothorax. When these are 

 frightened, they feign death and fall to the ground with their 

 legs stiffened and stretched out in a straight line from the 

 body. What, then, was Dr. Tower's surprise to find that all 

 but ten of Lot A beetles, creatures that were direct descend- 

 ants of multitaenita, were feigning death in quite correct 

 melanothorax fashion. The damp-heat environment had so 

 affected them through their parents that now, when the mo- 

 ment of fright came, they did not fold their legs up against 

 their bodies as their ancestors had done, but stiffened them 



1 Lot A produced 59 and Lot B 82 full-grown beetles. 



