60 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 6 



The great abundance of adults at this time (June 3) seemed to pre- 

 clude their being hibernated individuals. As stated above, Paspalum 

 was shown to be a true host plant and was abundant from very early- 

 spring. It seems safe to conclude that the first generation of larvse 

 are produced upon the roots of Paspalum and perhaps other native 

 plants, and that the weevils maturing from these are the ones to infest 

 the young rice in May and early June. The field of rice which was 

 just being flooded, and being occupied by adults for the first time on 

 June 3, was again examined on June 29. At the latter date adults 

 were very scarce but larvae were found in abundance at the rice roots. 

 The larvae were all of about the same size and apparently up to maxi- 

 mum size. Some of these larvae were kept on roots of live rice in cages 

 as late as July 15, by which time they had neither increased in size 

 nor changed to pupae. 



From this data we conclude that from 35 to 45 days elapse from depo- 

 sition of the egg until completion of the larval stage. I was unable to 

 determine the duration of the pupal stage. 



It is not impossible that a third generation is produced upon native 

 host plants, folloTidng maturity of the generation on cultivated rice. 



Control Measures. The only control measure followed to any 

 extent, during the past thirty years, has consisted in drawing off the 

 irrigating water in an attempt to destroy the larvae. Among the rice 

 growers themselves there is great diversity of opinion as to the effi- 

 ciency of this plan. Experienced growers claim full success from the 

 method, while others, equally as experienced, decry it as a dismal 

 failure. 



The writer believes that he was the first to detect the surprisingly 

 simple explanation of these diverse results. Briefly stated, this 

 explanation is as follows: 



If the injury by the larvae is in its incipiency and only a small pro- 

 portion of the roots has been severed, drawing off the water for a rea- 

 sonable time will destroy the larvae and, if replaced at the proper time, 

 will not perceptibly interfere with the growth of the plants. 



On the other hand, if injury by the weevil larvae has reached the 

 point where practically all roots are severed, drawing off the water 

 cannot result otherwise than disastrously to the plants for, with no 

 root system except a few small rootlets at the crown, the plants have 

 no way of getting sufiicient moisture to continue growth. In such 

 cases injury from drying occurs, far more severe, ordinarily, than the 

 injury done by the larvae when the water is left on. My examination 

 of a large number of fields in all cases confirmed this explanation. 



Every rice grower should be able to distinguish the degree of injury 

 to the plants and determine therefrom whether the water should be 



