302 SCIENCE FROM AN EASY CHAIR 



commercial value for this plant, and that those capsules 

 which happen to contain a grub and move are collected 

 from the ground by the native Mexican boys and sold as 

 curiosities. 



The moth (Carpocapsa saltitans) lays its eggs on the 

 Sebastian shrub, and the young grub, on hatching, eats 

 its way into the young fruit when the latter is still quite soft 

 and the seed unformed, and so leaves no hole to mark its 

 entrance. As the fruit swells the grub eats out the seed 

 and surrounding pulp of the segment of the fruit into 

 which it entered early in life. By the time the fruits are 

 dry and fall to the ground the caterpillar is fully grown. 

 Of course, it is only a very few of the capsules which are 

 thus invaded by a grub. 



The question very naturally arises, " Why should the 

 caterpillar put itself to the great muscular effort of 

 making the little capsule in which it is contained jump 

 and move over the ground?" It seems probable that 

 these movements are made in order to bring the capsule 

 from an exposed position when it falls on to the ground 

 where it might be crushed or eaten by some animal 

 into a position of shelter, either into a hole, or under some 

 stone or fallen wood. The warmth of the sun in an ex- 

 posed position excites the caterpillar to activity, which 

 ceases when it has reached the shade offered by some 

 protecting cranny. In the same way I have applied 

 artificial heat and, alternatively, shelter from heat, so as 

 to cause the movements or the resting of the jumping 

 bean in a London sitting-room. 



These things and others of absorbing interest may be 

 seen in the truly wonderful museum of Kew Gardens, 

 where perhaps the visitor will be disposed to spend more 

 time in cold weather than in the summer. The park at 

 Kew Gardens, with its splendid forest and lakes, and its 

 Italian tower, is one of the beautiful things of England, 



