TIIK r.ROAIi-HKAN WEKVIL. 



13 



test, beans were taken from })ot,s 20 daj^s after planting, and a live 

 adult found in one of its burrows in a bean tliat had germinated. 



When disturbed, the wee\ils have the habit of folding their legs 

 tightly and feigning death. On the plant they will fall to the 

 ground, but quickly become active. In the sack or on a table they 

 are apt to remain quiet, "playing possum" for some time, and it takes 

 quite a prod with a pencil or pin to make them become active. 



GERMINATION TESTS OF INFESTED BEANS. 



A number of tests were made to determine the effect of weevil in- 

 festation on the germinating power of the beans and at the same 

 time compare new seed and that held over a year. 



Table X. 



-Germination tests of infested and noninfested hrnns ; neio and 

 year-old seeds. 





New crop seed, percentage of 

 germination — 



Date. 



Old crop seed, percentage of 

 germination — 



Date. 



With 

 no 



wee- 

 vil. 



With 



1 

 wee- 

 vil. 



With 



2 

 wee- 

 vils. 



With 



3 

 wee- 

 vils. 



With 

 4 and 



5 wee- 

 vils. 



With 

 no 



wee- 

 vil. 



With 



1 

 wee- 

 vil. 



With 



2 

 wee- 

 vils. 



With 



3 

 wee- 

 vils. 



With 

 4 and 



5 wee- 

 vils. 



Apr. 26. 1916 



Nov. 20, 1916 



Dec. 1,1916 



Dee. 13, 1916 



98 

 98 

 96 

 86 

 100 

 92 

 98 

 98 



90 

 92 

 94 

 60 

 100 

 88 

 68 

 90 



60 

 68 

 86 

 54 

 92 

 88 

 26 

 88 



72 

 98 

 88 

 50 

 92 

 73 

 28 

 68 



"'87' 



"'52' 

 70 



Oct. 27, 1916 



Nov. 20, 1916 



Dec. 1,1916 



Dec. 13, 1916 



Mar. 22, 1918 



Oct. 17, 1918 



Average 



96 



100 

 90 

 88 

 84 



100 



94 

 90 

 70 

 64 



72 

 38 



86 

 90 

 90 

 56 

 89 

 54 



&8 

 90 

 90 



""75 



Mays, 1916 



Mar. 22, 1918 



Oct. 17, 1918 



Apr. 28, 1916 



24 



8 



44 



Average 



95.7 



82.7 



72.7 



71.1 



69.6 



93 



71.1 



76 



60 



59 









Average of infested beans 74 



Average of infested beans 66 



This table shows that as the number of insects per bean uicreases, 

 the percentage of germination decreases. The drop is about 20 per 

 cent from perfect beans to those infested with one weevil, and some- 

 what less for each weevil up to the maximum of 4 and 5 weevils, 

 which gives a germination of 60 or 70 per cent. The table also 

 shows that the percentage of germination is a little more with new 

 crop seeds than with those held over for a year. 



The table, however, does not show the reason for the low germina- 

 tion in the infested beans. In only a few cases does the insect actu- 

 ally injure the embryo or germ, but by far the greatest damage comes 

 from the fact that the holes made by the insects allow bacteria or 

 fungi to enter, which cause the beans to rot. In a number of cases 

 rotting takes place soon enough to prevent germination entirely, 

 but a large number of beans are killed also after the seed has actually 

 germinated, and before the shoot can get out of the ground. Eotting 

 of the seed is much worse during; cool or cold weather, when srermi- 



