108 Partner- yeasts 



Everyone knows the little beetles called "death- 

 watches" that make tapping noises in the wainscot. 

 The male thumps his head against the wood, signal- 

 ling to his desired mate — speaking, therefore, of love, 

 not of death. The larval death-watches bore in wood 

 and other dry materials, including books — poor 

 food ! Now, it has been shown that at the beginning of 

 the digestive part of the food-canal of the larval 

 death-watch there are two minute pockets which are 

 crammed with yeast-plants. These work on the un- 

 promising wood pulp, and there is a little brewery 

 inside the larval death-watch. Careful examination 

 showed Professor Buchner that there were no yeast- 

 plants in the eggs; yet they were always present in 

 the young grubs. The solution of this puzzle is almost 

 incredible. Associated with the egg-laying apparatus 

 in the female there are two minute reservoirs opening 

 to the exterior, and these are full of yeast-plants. 

 When an egg is laid, some yeast-plants are expelled 

 along with it, and they adhere to the rough surface 

 of the egg-shell. When the beetle-grub is ready to 

 hatch out, it nibbles at the egg-shell, and thus its 

 food-canal becomes infected with yeast-plants. A 

 little leaven goes a long way with the death-watch. 

 The details are interesting, but even more important 

 is the general fact that a partnership of yeasts and 

 insects has been demonstrated in scores of cases. It 

 is no "curiosity." 



The correlation of organisms is very important 

 practically, for there cannot be an evolving control 

 of life which does not give the intricacy of the web 



