E. J. BUTLER 9 



feeding by sucking out the juices through a minute bole bored by a tiny spear 

 which can be protruded from the mouth. That other such forms exist 

 besides the two already described is very probable, since they are as readily 

 overlooked by entomologists as by mycologists. They are neither insects nor 

 fungi, nor do they cause any such characteristic symptoms as would lead to 

 their presence being specifically looked for. In spite of their simple mode of 

 parasitism they can, as the rice worm shows, rank with the most harmful 

 enemies of plants yet described. 



Tylenchus angustus feeds, so far as can be ascertained, exclusively on 

 living rice. Attempts to grow it in artificial media have failed, and a search 

 through the infected area has equally failed to reveal it on any other plant 

 than rice. It can remain alive, in the absence of food, for considerable periods, 

 but its growth is very limited and no moults occur except those which were 

 due when removed from the living plant. After emergenc3 from the egg there 

 is some increase in size in water, but this never progresses to the first moult 

 The later larval stages increase little, if at all, in water. It is not certain 

 whether the final (sexually perfect) stage can reach fuU maturity in water if 

 liberated while still immature, but the perfect female may lay eggs for a short 

 time in water. Copulation does not occur in water, as many thousands of adult 

 worms have been kept under observation in this medium without any trace 

 of the sexual act having been seen. In dry air the worm can remain alive for 

 considerable periods, but it remains entirely pas!iive, neither moving, nor 

 feeding, nor gromng, nor copulating. There is, therefore, no multiplication 

 of the worm in these conditions, except that a few eggs may be laid in water 

 and a few of these may possibly hatch out into the first larval stage, though 

 as a rule only such eggs as are mature when removed from the plant seem to 

 hatch when totally immersed. Though the worm may remain alive and 

 wander considerably on various solid media for several weeks, no increase in 

 numbers has been obtained in this way, but further considerable trials will 

 be necessary before it can be concluded that artificial cultnre is not pcsoible. 



The worms may be induced to attack paddy at any time ot the year if 

 properly handled. Nevertheless there are great dift'erences in behaviour at 

 different seasons, and to understand these it is necessary first to describe the 

 life-history of the parasite when unable to obtain suitable living food. 



The non-parasitic life of Tylenchus angashts. 



Normally the active life of the worm, as indicated by the appearance of 

 symptoms of injury to the plant, extends from June to November in the 



