43Q POPULAR SCIENCE MONTHLY. 



sun-dew had their origin in the course of the evolution of the plant 

 world? Such a question will ever remain a mystery, and on its solu- 

 tion we shall be able merely to throw an occasional ray of light. Very 

 many plants have their stems or flower-stalks beset with glandular 

 hairs secreting sticky substances; an example in point, the clammy 

 cuphea of our fields which sticks to the fingers tenaciously if we 

 attempt to pluck its flowers. So far as known, the sticky secretions 

 serve the plant in no way other than making it unpleasant browsing 

 for herbivorous animals and ridding it of marauding ants, which 

 become stuck to the glands and seldom escape. Might not such a con- 

 dition have existed in the ancestors of the sun-dew ? Might not the acci- 

 dental catching of insects in this manner have formed the starting- 

 point for the habit which is now so essential to the plant? Pitchered 

 leaves are found too in many plants, and in many of them catch insects 

 by pure accident, for example, the Dischidia of the East Indies. It is 

 quite possible that further study of such cases may reveal new examples 

 of the insectivorous habit, or may discover plants which have an im- 

 perfect or partial dependence on insect food, and any such discoveries 

 would throw light on the development of the habit in its full-fledged 

 possessors. 



Marvelous as are the adaptations of the insectivorous plants, they 

 have not been all these years upon the earth without certain crafty 

 insects having learned not only to escape falling a prey to them, but 

 to use them to their own ends. The pitchers of the Californian 

 pitcher-plant are the home of a small moth which is provided with 

 sharp spurs on its middle legs, which enable it to crawl easily over the 

 slippery surfaces of the interior. So fearless has the moth become 

 that it even lays its eggs in the interior of the pitcher, and here, pro- 

 tected from all the manifold dangers of the outside world, they hatch 

 out in security. The young caterpillars spin a web over the slippery 

 surfaces and the projecting hairs, making a safe path for themselves 

 to the outside. There is a blow-fly which is able, too, to crawl over 

 the slippery surfaces by aid of peculiar claws which give it a good sure 

 footing. The grubs of this fly hatch out in the water of the pitcher 

 and, far from yielding themselves up as food, they live here their brief 

 term of larval life, and escape by boring a hole in the side of the 

 pitcher. 



In the South African hills grows a sort of bushy snn-dew, known 

 locally as the 'fly-bush' (Roridula). This plant is a large consumer 

 of insect food, owing to its size and the completeness with which twigs 

 and leaves and even parts of the flower are covered with glandular 

 hairs. Among its branches a spider has been found to spin its web. 

 Not content with the supply of flies from its web. however, the spider 

 goes forth upon the twigs of the fly-bush, and walking about in safety 



