48 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 81 



oiidary host, either as food or accidentally, such apparent exceptions 

 as in the case of Habronema being the unusual thing. We now take 

 up a group of worms which all fall in the family Filariidae, regarded 

 by those who recognize the superfamily Spiruroidea as described 

 above, as being part of the superfamily Filarioidea, the two super- 

 families being grouped on their affinities as the Filariata. 



FILARIIDAE 



In the Filariidae the customary mode of transmission of the worm 

 is by the bite of the secondary host, this host becoming infected when 

 it bites an infested primary host and in turn infecting a primary host 

 by biting it after an interval in which the worm develops to the in- 

 fective stage in the secondary host. It is to be expected, then, that 

 the biting Diptera will show up prominently in this list of intermediate 

 hosts, and we find a long list of such hosts recorded as transmitting 

 numerous species of filarid worms. Here we have a number of im- 

 portant worm parasites of man and dogs, including such filarids as 

 Wuchereria hancrofti and Loa loa of man, and the heart worm, 

 Dirofilaria immitis, a serious j^est of dogs in the hunting field. 

 Mosquitoes take first place in this group of Diptera, many species 

 transmitting W. hancrofti and D. immitis, while the tabanids, espe- 

 cially Chrysops spp., function for Loa loa. 



The Siphonaptera, Mallophaga, Anopleura, and Arachnida are all 

 charged with the transmission of filarid worms. 



DRACUNCULIDAE 



In the peculiar genus Dracunculus. including the guinea worm of 

 man, D. medinensis, the worms usually infest superficial body parts 

 of the primary host, and when these come in contact with water, the 

 worms release large numbers of embryos, some of which are swal- 

 lowed by copepods. The larval worms develop in these hosts to the 

 infective stage and when these hosts are swallowed by suitable pri- 

 mary hosts the worms develop to maturity. 



ARTHROPODS AS INTERMEDIATE HOSTS OF 

 ACANTHOCEPHALIDS 



The acanthocephalids quite generally utilize at least one inter- 

 mediate host, and sometimes two such hosts, the second one a fish, 

 amphibian, or bird in some cases, in their life history. These first 

 intermediate hosts are sometimes snails or leeches, but in most of the 

 reported cases the first intermediate host is an arthropod. The follow- 

 ing list shows the reported hosts for the species having known life 

 histories : 



