308 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 15 



each were collected from the fore intestines of the grubs. These were 

 dried, weighed, ignited and weighed again and the loss from ignition 

 considered as representing the approximate proportion of plant tissues, 

 by weight to the total material found in the fore intestines of the in- 

 sects. The loss by ignition of the soil from- which these larvae were 

 collected was about equal to the per cent of ash in the grass roots and 

 for our purjDOse these factors can be considered to offset each other. 

 These figures indicate that plant tissues constitute about 67.33 per 

 cent, by weight of the total material constnned by the larvae. 



Analysis of Material Eaten by Larvae of P. japonica 



Total weight of food collected 21.4134 grams 



Dry " " " " 15.4769 " 



Ash remaining after ignition . .• 5.0556 



Loss from ignition 10.4213 



Examination of the material contained in the fore part of the alimen- 

 tary canal indicates the soil particles and pieces of plant tissue to be 

 relatively uniform in size. The greatest variation occurred in those 

 tissues which were partially decomposed. The following data on the 

 extremes in size of particles found in the fore intestine are in each case 

 based on fifty measurements: 



Fresh plant tissue minimum length 0.45 mm. 



maximum " 1.22 mm. 



Fresh plant tissue minimum width 0.25 mm. 



maximum " 0.36 mm. 



Soil particles minimum length ■ 0.72 mm. 



maximum " 1.125 mm. 



Soil particles minimum width 0.327 mm. 



maximum " 0.875 mm. 



In order to determine the relative number of pieces of fresh plant 

 tissue, decaying vegetable matter and particles of soil composing the 

 aggregate in the fore intestines of the larvae, determinations were 

 made of the number and character of the particles obtained from twenty- 

 five grubs. The larvae were collected from grass sod May 20th, kill- 

 ed by dropping in boiling water, and dissected immediately afterward. 

 To separate the fresh plant tissues from those which were dead or 

 partially decayed, it was necessary to stain and compare the cellular 

 structure of the pieces found in the insect with the structures in fresh 

 root tissues taken from the plants where the larvae had been feeding. 

 The following tabulated statement indicates the approximate ntmiber 

 and character of the particles of material found in the fore intestines 

 of the larvae: 



Total number of pieces of fresh plant tissue 1375 64.3% 



" " " decayed plant tissue 419 19.0% 



" " " mineral matter 344 16.0% 



