86 ECONOMIC ZOOLOGY AND ENTOMOLOGY 



The guinea-worm, Filaria medinensis, referred to on an 

 earlier page, is a member of this group. It has been known for 

 many ages, and is thought to be the " fiery serpent" mentioned 

 by Moses. It lives in the connective tissues, where it attains 

 a length of two or three feet. Its diameter is about one and 

 one-half millimeters. When it is ready to produce young it 

 usually descends to the feet or the lower part of the legs of the 

 host or the part most likely to come in contact with the water. 

 Here it burrows out to the surface, often producing serious 

 sores. The intermediate stage is passed in the body of 

 Cyclops, a small fresh- water crustacean. 



There are several other species of Filaria that are parasitic 

 in man but they are of less importance. Filaria loa is an inter- 

 esting species that lives in the connective tissue just under 

 the skin and travels about from one part of the body to 

 another, occurring most commonly about the eyes, where 

 their presence may cause irritation and congestion. 



Classification of Nemathelminthes. This branch may be 

 divided into three classes, the Nematoda, Nematomorpha and 

 Acanthocephala. The class Ch&tognatha (Gr. chaite, hair; 

 gnathos, cheek) or arrow-worms, is usually included in this 

 branch but the relationship of the group is very uncertain. 



The Nematoda (Gr. nema, thread; eidos, likeness) are by 

 far the most important and include all of the forms that have 

 just been described, with the exception of the hair-snakes which 

 belong to the second class. 



The Nematomorpha (Gr. nema, a thread; morphe, form) 

 include the hair-snakes, the larvae of which, as we have already 

 noted, are parasitic in insects. One common species, Mermis 

 albicans, frequently occurs abundantly enough in grass- 

 hoppers to be of some importance in their control. It is 

 probably this species, too, that at times causes so much alarm 

 in some regions when the "cabbage snakes" appear in great 

 numbers. When these round-worms occur on cabbages or 

 other vegetables it means that the insect that acted as their 

 host was probably resting or feeding on the plant when the 

 parasite left it. As soon as they can they pass into the ground 



