THE PAGE OF NATURE. 233 



attacking insects, seem to be one of the powerful and 

 efficient checks provided by nature for restraining within 

 due limits the increase of creatures, which, owing to their 

 extraordinary fecundity, rapid development, and un- 

 bounded rapacity, would otherwise prove a terrible 

 scourge. 



The insect Sphaerias are found in different countries. 

 In Australia, where a gigantic species occurs on an enor- 

 mous larva frequently found beside the banks of the 

 Murrambidgee, in North America, and in China, these 

 deadly parasites are developed upon insects of different 

 tribes. They form a favourite medicine in China, where 

 a bundle of the fungi, with the caterpillars attached to 

 them, is placed in the stomach of a duck, which is then 

 roasted and eaten by the patient as a cure for internal 

 complaints. There is a peculiar disease called muscar- 

 dine, affecting the silk-worm in Syria and China, before 

 they have woven their cocoons, which sometimes proves 

 fatal to thousands of these delicate creatures. It not 

 unfrequently happens that the silk-grower loses his 

 whole stock of worms from this cause alone. This 

 disease is caused by the mould-like filaments of the 

 Botrytis bassiana. These filaments grow with great 

 rapidity within the body of the animal they attack, not 

 only at the expense of its nutritive fluids, but after its 

 death ; all the interior soft tissues appear to be converted 

 into a solid mass of mycelium, from which arise one or 

 more aerial receptacles of the spores. It sometimes 

 happens that the caterpillar is only partially affected by 

 this fungoid growth, or only to such an extent as not to 

 destroy the organs immediately essential to its life, in 



