April, '16] SANDERS AND FRACKER: LACHNOSTERNA RECORDS 



259 



partially empirical and partially based on very meagre information. 

 This report is preliminary and the more promising lines of work will 

 be continued. Attempts will also be made, where possible, to apply 

 the results in a practical wsty. 



In these experiments we tried to find out whether white grubs 

 had daily or seasonal habits, such as those of cutworms, what was 

 their relation to temperature and to moisture, what foods they 

 would eat, and what part of the plants they preferred. Efforts were 

 also made to control them by stomach poisons, contact insecticides, 

 and repellents. No work was done with fumigants as this phase of 

 the subject has been carefully studied by previous workers. 



Two forms of cages were used, most of the work being done with 

 ordinary flower pots. In working with this type of cage, which 

 Davis has found to be most satis- 

 factory for rearing the grubs, it is 

 necessary to empty the flower pot 

 at each examination. In all cases 

 where continuous observations 

 seemed desirable, glass cages (Fig. 

 12) were used in which the earth 

 was placed between two vertical 

 glass plates less than one-half inch 

 apart. Opaque shields were used 

 to keep out the light except at the 

 moment the grubs were examined. 

 It was found possible to regulate 

 the distance between the glass plates 

 so that any size of grub could be 

 seen from at least one side at any 

 time and still leave sufficient free- 

 dom for the grubs to move actively 



back and forth. When young corn plants were placed in the soil 

 between the plates, the roots were readily eaten and usually completely 

 destroyed. 



The experiments may be divided into seven groups, all the important 

 results so far secured being given below: 



1. It was found that grubs have no daily migration, such as cut- 

 worms. They were never observed either eating or active late in 

 the evening, early in the morning, or on cold days. Their movements 

 reached the maximum during the heat of the day. There does not 

 seem to be a vertical migration in relation to temperature changes, the 

 larvse in sod usually remaining close to the surface of the soil at all 

 times but moving about and feeding only during warm weather. 



Fig. 12. Cage for Biological Studies 

 of White Grubs. 



