Since newly hatched larvae cannot penetrate the smooth surface of the medium, it 

 was necessary to thoroughly scratch the surface of the medium before the eggs were 

 placed on it. This procedure was accomplished by using a small tool consisting of a 

 plate with numerous sharp-pointed nails soldered to it. When this device was passed a 

 few times over the surface of the medium, many hundred shallow fissures were formed 

 in the medium. Thus, the young larvae could penetrate the medium. 



With the egg-planting device, more than 1,000 eggs per minute could be planted in 

 the diet medium as compared with 500 per hour by the hand method. 



In a test comparing the effectiveness of machine planting with that of hand planting, 

 6, 000 eggs were divided into two groups of 3, 000 1 20. One group was planted by hand 

 and one by the planting device described above. 



The data from this test were as follows: 



Dishes planted 



Dishes that became contaminated 

 Time necessary for planting 

 Adult weevils that emerged 

 Average weight of adults 



These data show that mechanical planting of eggs had little effect on weevil development. 



In addition to the great saving in labor cost furnished by the egg-planting machine, 

 the data show that a second important advantage was realized. The mechanical planter 

 was responsible for a reduction in the number of petri dishes that become contaminated 

 with molds and yeast. Most of this type of contamination is caused by airborne spores. 

 The mechanically planted plates were open and exposed to such contamination for less 

 than 2 seconds. In contrast, the hand-planted plates were open and exposed for as long 

 as 5 minutes. 



By hand 



Mechanically 



38 



41 



17 



4 



4^ hours 



5 minutes 



1,086 



1,059 



15.3 mg. 



14.7 mg. 



10 



