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husk, radicle and plumule. They were also seen eating the blades 

 which had come above the ground. The glass cylinders had removable 

 ends of perforated zinc of fine mesh. A few larvae passed through 

 the perforations at the bottom although these were small Within 

 the cage they tunnelled freely to a depth of six or seven inches. After 

 a week, when all the com appeared to have germinated, and both 

 radicle and plumule were of some length, the cylinders were removed 

 and the state of the seedlings ascertained. These were separated 

 out carefully and placed in water. The soil was removed as far 

 as possible by gentle washing, and each seedling examined in turn. 

 Care had been taken that no other creatures were present in the soil 

 capable of damaging the oats. There were usually about 25 larvae 

 present. A typical result is given: 



34 seedlings apparently sound. 



11 had radicle or rootlets more or less eaten away. 



39 had plvimule cut through or bitten into. This includes a number attacked 

 in the blade, above ground. 

 8 seeds were attacked. In some cases this had been effected before germi- 

 nation, in others, afterwards. In some of these the food store was com- 

 pletely eaten out, in others only partially so. 



_^ 



Equal to 63 per cent, of the plants damaged. 



The factors contributing to such a result appear to be: 



(1) The absence of decaying or other vegetable matter, with con- 

 sequent restriction to the crop for food supplies. 



(2) The large proportion of larvae to the cubic content of soil — 

 two dozen to about 1| cubic feet of soil. 



(3) The confinement of the larvae to a limited amount of space; 

 it was not possible for them to leave the cages. 



A further factor to be noted is the favourable conditions of warmth 

 and suitable moisture, inducing rapid germination. This would be 

 of some importance in the field in favour of the crop "growing away" 

 in a proportion of cases before the damage done became irremediable. 



In other experiments of this nature with germinating oats, clover, 

 or timothy grass, the numbers of larvae used were very much greater, 

 with correspondingly serious damage. It was found subsequently in 

 examples of very severe attacks upon crops in the field, that the numbers 

 used in these experiments were in excess, and that serious loss may 

 ensue where the numbers, in average samples of an affected area, are 

 about 10 to 15 per square foot of surface (see p. 133). 



