206 STUDIES IN INSECT LIFE, ETC. 



harmless, but one, a Coccidium (there is no more 

 popular word for it), is the cause of disease in 

 the grouse-chicks. 



Since this disease was first found in the young 

 grouse much has been written about it in the 

 newspapers, and in nearly every case the writer 

 has taken the Coccidium to be a Coccus. Now 

 a Coccus is no more like a Coccidium than a 

 crocus is like a crocodile. The Coccus is a bac- 

 terium, a vegetable, and it has a simple life- 

 history ; the Coccidium is a Protozoan, an animal 

 with, as we shall see, a very complicated life- 

 history. 



Dealing first with the Coccidiosis : 

 One of the aims of grouse-preservers is to have 

 numbers of healthy young grouse-chicks in order 

 to produce stocks of strong birds. Bad seasons 

 for grouse are partly due to epizootics among 

 the young broods in the spring, and the chief 

 cause of mortality among grouse-chicks is a 

 small, one-celled microscopic animal parasite, 

 Eimeria (Coccidium) avium. This parasite pene- 

 trates the lining membrane of the gut of the 

 bird, and gradually destroys it, thereby setting 

 up digestive troubles in the form of intestinal 

 inflammation (enteritis), accompanied by acute 



