12 THE RICE WORM (tYLENCHUS ANGUSTUS) AND ITS CONTROL 



When kept under intermediate conditions between total immersion and 

 dryness, life may be maintained for several months. Kept on slides under 

 bell jars in a saturated atmosphere some have been found still alive after 

 4 months. Under such conditions they have a certain degree of motility, as 

 will be explained later, and they live decidedly longer than when totally 

 immersed, though less than when desiccated. 



Both longevity and motility, away from the host plant, are influenced by 

 other conditions than moisture. Temperature and light are amongst these. 

 In one experiment a number of worms that had been dried on the host plant 

 for two months were sown in tap water on several slides. All the worms were 

 from the same piece of infected peduncle. They were sown on January 29th, 

 1917, and resumed active motility after about half an hour. Two of the 

 slides were placed in an incubator at 31°C., in a saturated atmosphere, 

 in the dark. Another was kept in a saturated atmosphere on the bench 

 near a window ; and a fourth close by under similar conditions except that 

 it was covered with a dark shade. The bench temperature varied from 

 16° to 19''C. during the next week and then gradually rose, reaching 

 a range of 21° to 23°C. after a month. On January 30th the worms in the 

 incubator were moving actively, as were those exposed to light on the bench, 

 while those in darkness on the bench were very sluggish. The following day 

 these differences were accentuated. The darkened worms in the incubator 

 were exceedingly active, while those in darkness on the bench had ceased 

 swimming and were merely coiling and uncoiling or bending from side to side 

 slowly. Those exposed to light on the bench were swimming a little less 

 actively than those in the incubator. Here both light and warmth had stimu- 

 lated activity, the latter somewhat more than the former. On the 23rd of 

 February all the worms in the darkened chamber on the bench were dead, 

 while those exposed to light were still alive in fair numbers though now only 

 moving sluggishly and mixed with a good many dead. In the incubator, on 

 the other hand, most of the worms were still living and very active in the 

 water. The drops were replenished on this day. A month later some were 

 still alive and moving in the drops in the incubator. By the 13th May there 

 was only one worm left alive in the lighted chamber at laboratory temperature 

 (now ranging from 27° to 29°C.) and that one had migrated from the drop, 

 while there were still many in the incubator. The water in the latter had 

 dried to a thin film in which no living worms were left, but living worms were 

 scattered over the rest of the slide, singly or in small groups, and feebly motile. 

 On adding water they promptly became actively motile again. As the incu- 

 bator bad now ceased working owing to the rise in temperature, the slides 



