THE RICE WATER-WEEVIL. 9 



stands deepest. As previously mentioned, such places are most 

 attractive to the adults. Where the adults occur most numerously 

 the larva? must be expected to follow in great number. In conse- 

 quence the severity of the larval infestations is shown by a yellow 

 cast of the leaves extending in broad streaks along dead furrows, 

 while spots and areas of yellowish plants also become visibly ap- 

 parent within the hollows and sinks of the land. These signs of 

 injury have appeared in fields after 20 days of flooding, but ordi- 

 narily the larvae do not become numerous enough to cause much 

 damage until the water has stood for at least a month. 



If man} r of the roots are cut off from a plant (fig. 1, e), its growth 

 is stunted, but as the growing rice plant possesses a strong vital power 

 new roots are put out to replace the ones destroyed, and on the cessa- 

 tion of attacks the injured plant revives, or is said to " recover," 

 and makes a belated growth, usually resulting in late heading. Much 

 of the unequal growth of the plants in the fields, as well as the irreg- 

 ular maturity of heads, is accountable to the detrimental effects of 

 the larval attacks. Harvesting must necessarily be delayed until all 

 the heads are ripe, thus involving the risk of loss to the normal yield 

 from storms or other causes. 



Furthermore, the attacks on the roots of tender young plants pre- 

 vent proper stooling or production of stems. In comparison with 

 normal plants, often less than half as many steins grow from a stool 

 that has suffered damage. Shortage of heads is therefore caused by 

 the failure of badly injured plants to produce a full quota of stems. 

 The fact that the larvae are largely responsible for a great deficiency 

 of yield in this respect will impress a comprehension of the amount 

 of loss caused by the insect. 



DEVELOPMENT OF STAGES. 



The length of time required for the development of the weevil 

 from a freshly laid e<ag has been estimated by Mr. Hood to be about 

 10 weeks. Judging from the first occurrence of larvae in fields after 

 1 to 3 weeks of flooding, a period not to exceed 10 days would 

 probably be ample time for an c^,<x to hatch subsequent to deposition. 

 Development is hastened with the advance of hot weather when the 

 water and soil become warm. Usually not until about six or seven 

 weeks after flooding do many of the larvae attain full growth and 

 appear ready for pupation, although pupa 1 have been found in a field 

 that at the time had been irrigated for only five weeks. In prepara- 

 tion for the pupal stage the larva forms a cell in the mud among the 

 roots or at the tip of one. and Mr. Hood has asserted that the pupa 

 passes two <>r three weeks before it matures and the emergence of the 

 adult takes place. 



