THE RICE WATER-WEEVIL. 7 



the underside uneaten. These scars are very narrow, being in fact 

 no wider than the spread of the mandibles, but they vary in length 

 from a small fraction of an inch to more than 2 inches, depending 

 on the time in which the insect engages in feeding. When the thin 

 underside dries within the scar, it splits and forms an open groove 

 throughout the injured space. The leaves suffer no serious ill effects 

 from being fed upon unless the scars become numerous enough to 

 cause wilting and dying. Adults prefer tender young plants rather 

 than the coarser strong growth. 



MATING AND OVIPOSITION. 



Throughout the period in which the weevils remain in evidence, 

 mating takes place on nearly all occasions when a male and female 

 happen to meet, and this usually occurs on a leaf. The gravid 

 females crawl down the stems of the plants and evidently deposit 

 their eggs singly in a puncture that is first gnawed in a root. Mr. 

 Newell has mentioned that he has seen adult weevils which he be- 

 lieved to be females make punctures on the stems below the water 

 line. Mr. Hood and the writer have watched the operations of 

 females when they apparently undertook to oviposit on rice roots 

 within glass tubes. Each weevil thus observed deliberately sought 

 out a place on a root and ate into it for about a minute. Then she 

 reversed her body, gripped tightly, and pressed the tip of the abdo- 

 men over the hole which she had eaten out. Mr. Hood has recorded 

 that he saw the ovipositor in the form of a brown tubular organ in- 

 serted into the hole. In this case the weevil remained in position 

 without any apparent movement for 50 seconds before the ovipositor 

 was withdrawn. The writer has not been able to see the ovipositor 

 extended nor to detect an egg with certainty. The weevil may climb 

 up above the water after each operation and rest for a long or short 

 period, or continue her actions among the roots for a while. One 

 weevil stayed among the roots for 45 minutes. 



The device that was designed and used by the writer for observing 

 the method of oviposit ion by the weevils is illustrated in figure 2. 

 In its construction a long lamp chimney was placed upright in a 

 saucer and cemented at the base with plaster of Paris. A wire sup- 

 port with the top bent into a loop of the proper size for steadying a 

 closed-bottom glass tube, one with an inch diameter being used to 

 hold the roots of a young rice plant in water, was first placed in the 

 center of the saucer. The lower end of the support was also bent in 

 a spiral to secure firmness after being set in the plaster. By means 

 of a siring tied to the upper part of the tube, it could be lowered 

 through the top of the chimney into a standing position within the 

 wire loop and also removed to permit close inspection of roots and 

 insects inside of it whenever desired. 

 4U993 — Cir. 152—12 2 



