184 DISEASES OF DOMESTICATED BIRDS 
H. lanceolata, singly or together cause injury among geese in Europe. 
Davainea friedbergeri causes great losses among pheasants. _ ; 
Life history. From time to time the tapeworm in the intestine 
of the chicken discharges ripe segments filled with eggs, which are 
voided in the feces. ‘To maintain the life cycle it is necessary that 
the tapeworm eggs be taken with the food into some creature known 
as a secondary host. In this host the embryos escape from the eggs 
and migrate to some organ where they form a cyst-like structure 
known as a cysticercoid. The life cycle is completed in case the 
intermediate host is eaten by a chicken in which event the cysticercoid 
develops into the adult form. 
Comparatively little is known about the secondary hosts of tape- 
worms of poultry. Of the five species of tapeworms that have been 
reported in chickens in the United States, the intermediate host of 
but one has been discovered. It has been determined that the inter- 
mediate host of Choanotenia infundibulum is the common house 
fly, Musca domestica. 
The intermediate hosts of a number of tapeworms of birds re- 
ported as occurring in other countries have been discovered. Thus 
a slug is necessary for the life cycle of Davainea proglottina, a 
chicken tapeworm. The intermediate hosts of certain tapeworms 
of the duck have been found to be various species of fresh water 
crustaceans. 
In general, the intermediate host is to be sought among the various 
insects and other forms of animal life to which the infested birds have 
access such as snails, insects, crustaceans or worms. 
Symptoms. These vary to some extent in different birds ac- 
cording to age and the degree of infestation. A few worms are not 
harmful to the bird and can hardly be noticed. Young birds are af- 
fected more seriously than old ones. In moderate infestation the 
bird is always hungry and experiences excessive thirst. Restless- 
ness is marked and doubtless accounts for the lean condition of the 
bird. Heavily infested birds show such symptoms as drooping 
Wings, emaciation, ruffled feathers and isolate themselves from the 
flock: 
The condition of the feces is more or less altered in tapeworm in- 
festation. Heavy infestation causes inflammation of the intestine 
and diarrhea with mucous droppings. The secretion is at first clear, 
transparent, semi-liquid and slightly whitish in color. Later the 
mucus becomes brownish yellow in color due to hemorrhage caused 
sy the worms, and this coloration constitutes one of the most char- 
