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njf'I^TIKICATION AND BTOLO(]Y 01'^ FJfKF,- LIVING NKHATODffi 



Free-living nematoder;, as the term vrill be used here, are defined as 

 nanatodes found in soil, in decayinf'; plant tissue, and in similar 

 habitats, but which do not feed on living plants. Discussion is limited 

 to the most common genera. 



Free-living nematodes are found in all agricultural soils without 

 exception, and also are found in other locations where food is available, 

 as in manure piles, compost heaps, and other places where access can be 

 had to dead plant or animal material. \iJhile not quite so ubicuitous as 

 bacteria or fungi, they can still be found in many odd places where any 

 sort of food has been present for a considerable time. This includes 

 some very strange habitats indeed; one of the oddest being in the felt 

 mats which were used in German taverns for parking beer steins between 

 drinks. Another form is found in paperhangers ' paste; another in 

 pitchers of pitcher plants; and another in vinegar, etc. Occasionally 

 they may be something of a pest. In a shipment originating in Argen- 

 tina, Dr. Steiner found nematode bodies in great abundance in canned 

 tomato paste. Undoubtedly, they also occur in other food processing 

 operations where the sanitation is not all that might be desired. 



In agricultural soils, free-living nematodes are often very niimerous, 

 counts of from several to hundreds per gram of soil not being unusual. 

 For the most part, little is known of food habits. However, it is a 

 fair assumption, with some evidence to support it, that many live on 

 bacteria. Others are predators, feeding by killing other nematodes. 

 Possibly others may feed on dead plants directly, though the evidence 

 for this is scanty. 



The nematologist working on agricultural problems will encounter free- 

 living forms in the soil, in decaying plant tissues, and at times in 

 apparently healthy plant tissues. Nearly every sample of alfalfa stems 

 and leaves collected on a field trip in Virginia and examined for stem 

 nematodes had a number of specimens of Panagrellus . 



With practice, it is easy enough to identify free-living nematodes to 

 genus, but identification to species is difficult or often impossible. 



For the Cephalobidae, an aid to identification is Thome's paper, "A 

 Hevision of the Nematode Family Cephalobidae, Chitwood and Chitwood, 

 I93U." (Proc. HeLninthological Soc. Washington. U(l): I-I6 of 1937). 



Genera of the Aphasmidia most comnon in soil samples are Flectus , 

 Fononchus (and subgenera) and various Dorj^laimina. The Dorylainina 

 include a large nuifiber of genera which are best separated by the use 

 of "A Monograph of the Nematodes of the Superfamily Dorylaim.oidea, " by 

 G. Thorne (Capita Zoologica 8(5): 1-261 of 1939). "A Monograph of the 

 Nematode Genera Dor:/laimns Du.jardin, Aporcelaimus n.g., Dorylain'oides 



