NO. 2258. TAENIOID CEST0DE8 OF DOGS AND CATS— HALL. 



75 



Hosts.— Primary : Canis familiaris, C. mesomelas, Felis srjlvestris 

 (F. catus), F. catus (F. catm domestica), F. inanicnlata, Homo 

 sapiens. Secondary : Tricho- 

 dectes cani s, Ctenocephalus 

 canis. Pulex irritans. 



Location. — In small intestine 

 of primary host. In the visceral 

 cavity of secondary hosts. 



Locality. — Cosmopolitan. 



Life history — Eggs developed 

 by the adult worm in the in- 

 testine of the primary host were 

 once supposed to be ingested by 

 the secondary hosts either on 

 the skin of the primary host, 

 where it was soiled by feces, or 

 from the gravid segments di- 

 rect. Melnikov (18G9) has 

 shown that TricTiodectes eats 

 the eggs as it feeds on the skin 

 of the dog, but Joyenx (1916) 

 has demonstrated that fleas in- 

 gest eggs while the fleas are 

 larvae feeding on debris, the 

 adult flea being unable to ingest 

 a tapeworm ^^g. In the digest- 

 ive tract of the secondary host 

 the embryo escapes and makes 

 its way to the visceral cavity 

 where it develops into the tiny 

 larva, called Cryptocysti'^ 

 trichodectis. When lice and 

 fle«s infested with those larvao 

 are ingested by the primarj' 

 host, the larval head passes to 

 the intestine and gives rise to 

 the strobilate worm, 



SYNOPTICAL KEY. 



The tapeworms of the dog, 

 cat, and some related carnivores 

 may be separated into the fol- 

 lowing groups and genera by the use of the appended key from Hall 

 (19165), (corrected for stenographic errors involving Dipylidium 

 fttsqualei and D. chyseri), which is intended to designate the rela- 



FlG. 80.— DiPYUDIUM CANINUM. ORAVID SEGMENT. 



Enlarged. After Diamark, lSOn'». 



