100 



Development. — The larval stage {Cercocystis H. diminutse) occurs in larval and 

 adult meal moths (Asopia farinalis); in young and adult earwigs (Anisolabis annu- 

 lipes); and in adult beetles (Acis spinosa and Scaurus striatus). 



Geographic distribution. — Massachusetts, Pennsylvania, Nebraska, Iowa, Dis- 

 trict of Columbia, Maryland, Brazil, Italy, Germany, France, Austria. 



This parasite is certainly more common in man in this country than 

 has heretofore been assumed, but fortunately it seems to be one of 

 the most harmless and most easily expelled tapeworms occurring 

 in man. 



From present evidence, the rats and mice are looked upon as the 



Fig. 30.— Encysted cystic stage of H, diminuta: caud,, caudal appendage; ct/st., adventitious capsule inclos- 

 ing the cercocystis. Enlarged. (After Grasai & Eovelli, 1892a, pi. 4, fig. 1.) 



regular hosts for this worm, and hence as the natural reservoir of 

 the infection. The intermediate host becomes infected from the 

 rodents and then transmits the infection to man. 



It might be mentioned that as yet no extensive study has been 

 conducted in the United States to differentiate clearly the various 

 species of Hymenolepis found in our rats and mice. The possibihty 

 is therefore not entirely excluded that some of our cases of Hymeno- 

 lepis diminuta may eventually be shown to be referable to other 

 species of the same genus. 



