85 



feeding upon tne bloom of clover and other late-flowering plants, it 

 has always been a question of interest whether these widely scattered 

 parent beetles have deposited their eggs before leaving the corn fields 

 in which they were bred, or whether they return to such fields for 

 oviposition ; and an attempt was made in 1904 to collect data which 

 should throw light upon this question. The amount of material ac- 

 tually obtained is too small for final conclusions, but is nevertheless 

 of sufficient value for report. 



Collections of adult beetles were made August 26 and September 

 5, 6, and 7, from eleven fields, four of which were in corn, four in 

 clover, two in oats stubble, and one in swamp grass. Three hundred 

 and forty-six of the specimens obtained were dissected to determine 

 their stage of maturity. Seventy-one percent of those collected in 

 corn fields and 82 percent of those from fields not in corn were fe- 

 males. The difference in this respect was considerable, and it was at 

 least apparent that the females were not remaining in the corn fields 

 in larger proportion than the males. The ratios of mature to immature 

 females in the two situations were 4 percent mature for collections 

 made in fields of corn and ten percent for those made in other fields — 

 a considerable difference, it is true, but of a character to indicate 

 that females were leaving the corn fields very generally before their 

 ovaries were ripe, and that they must consequently return to the corn 

 to deposit their eggs, if these are laid wholly or mainly in corn. 



In view of the fact that the parent beetles of the corn root-worm 

 leave the corn field in large numbers in search of food while they are 

 still immature, becoming especially abundant where blossoming plants 

 are massed, as in the clover field, and occurring also in considerable 

 numbers on swamp grasses, upon the roots of which they have some- 

 times been suspected to breed, search has been repeatedly made of the 

 roots of such plants at times when the presence of the insect in some 

 stage, or evidence of its injury to the roots, might be expected if it was 

 capable of breeding in other plants than corn. For example, Sep- 

 tember 8, 1904, Mr. Taylor dug up thirty stools of clover and thoroly 

 searched their roots and the earth about them in a field from which he 

 had just collected large numbers of adult Diabrotica longicornis, but 

 he could find no eggs or beetles in the ground or any trace of root- 

 worm injury to these plants ; and another field assistant, Mr. G. E. 

 Sanders, devoted the greater part of four days, July 16 to 19, 1906, 

 to a similar examination of the roots of grasses, sedges, club-rushes, 

 composite plants, and a variety of field weeds, in and immediately 

 about corn fields in which the corn root-worm was abundant. He also 



