RELATION OF INSECTS TO THE PARASITIC WORMS 73 



cavity and this is probably the stage in which the parasite is trans- 

 ferred to the bird ; whether as a result of ingestion of the louse by the 

 swift, or as a result of the active migration of the worm from the 

 louse while the insect is engaged in biting, has not been determined. 



Filaria martis Gmelin, 1790 



Filaria martis (or Filaria quadrispina) according to various writers 

 occurs in its adult stage beneath the skin and in the abdominal and 

 thoracic cavities of Mustela foina. Baldasseroni (1909) has found filaria 

 embryos in the intestine of ticks (Ixodes ricinus) taken from a marten 

 harboring the adult nematode, and he suggests that ticks may act as 

 intermediate hosts. As in the case of AcantJiocheilonema grassii, further 

 evidence is necessary before ticks can be considered to play a part in the 

 life history of Filaria martis. 



Dirofilaria immitis (Leidy, 1856) Railliet and Henry, 1911 



This nematode, sometimes erroneously listed as a parasite of man, 

 lives in the right side of the heart and pulmonary artery of the dog. 

 The larvae are found in the circulation, most numerous at night as in 

 the case of Filaria bancrofti. As would be expected from the location 

 of the adult parasite it may give rise to serious symptoms, and affected 

 dogs commonly succumb to the disturbances which it causes. It is a 

 troublesome parasite among hunting dogs in the Southern United States. 

 Noe (1900) showed that the larvae of this nematode continue their de- 

 velopment in certain species of mosquitoes when sucked up with the 

 blood of infested dogs. In 24< to 36 hours after reaching the stomach 

 of the mosquito the larvae pass into the Malpighian tubules. They 

 undergo a certain growth and development in this location, and 11 or 12 

 days after reaching the mosquito they break out of the tubules, enter 

 the body cavity, and migrate to the labium. From the labium of the 

 mosquito they reach their final host, the dog, in the same manner as 

 F. bancrofti reaches its human host, namely, by breaking through thin 

 portions of the cuticle of the labium at tlie time the mosquito is engaged 

 in biting its victim and then penetrate the skin, finally migrating to the 

 heart. Mosquitoes infested with the larvae of D. immitis are commonly 

 killed by the parasites owing to their destructive action on the ^lalpighian 

 tubules, Noe having observed that only about half the nios(|uitoes that 

 become infested survive. In Italy the common intermediate hosts appear 

 to be Anopheles maculipennis, A. bifurcatus. A, (Myzorh/jnchus) sinensis 

 pseudopictus, and A. (Mijzomyia) superpictus among anophelines; culi- 

 cines, according to Noe such as Culex penicillaris, C. malariae, and ex- 

 ceptionally C. pipiens, can also act as intermediate hosts. 



