OTHER SOIL ANIMALS - The Soil - page 107

F IG. 36
The eelworm Longidorus; an adult female. (Photograph K. Evans.)
Microbial feeders, such as Rhabditis , have a narrow gullet for swallowing bac-
teria and algae. Predators like Mononchus have strong teeth in the buccal cavity, and
can attack relatively large prey such as protozoa, rotifers and smaller nematodes. One
individual was found to have consumed 83 larvae of a plant-parasitic eelworm in a
day and 1322 in 12 weeks. A third type, typified by Tylenchus and Dorylaimus , has
a sharp stylet which is used to pierce and suck the juices from fungi and roots and
sometimes from other animals. The lips are pressed against the cell wall which is pen-
etrated by repeated thrusts of the stylet. Digestive enzymes are then injected into the
plant and the cell contents are sucked back.
This last mode of feeding has much in common with that of underground frog-
hopper and cicada larvae. It has been suggested that every kind of plant has its own
particular species of root nematode, and that their underground 'grazing' effect is
grossly underestimated in comparison with the effects of most phytophagous insects
simply because their feeding is unobserved. Add to these the predators, microbivores
and omnivores and one can begin to perceive the diversity of the soil nematode fauna
that might inhabit a flower-rich meadow.
The species that attack cultivated plants are best known because much work has
been done to elucidate their life histories, to estimate their populations, and to find
ways of controlling them. There is a complete sequence of forms from those that are
fully mobile as adults - the vagrant eelworms that graze intermittently and superfi-