48 
seems that the destruction of the tuber-moth eggs and larvae is more 
accidental than natural. 
Several species of spiders which are found in the fields spin webs in 
which dead tuber moths have been noticed, and in a few cases the 
spiders have been observed killing moths caught in the webs. 
ARTIFICIAL CONTROL. 
INDIRECT METHODS, GOOD FARMING. 
A study of the literature of the tuber moth shows that many writers, 
beginning with Capt. Berthon (1), have recommended good farming 
and careful harvesting and storing of tubers as the best remedies 
against the tuber moth. The powers of reproduction of this insect 
have given weight to these arguments, and a study of cultural methods 
in relation to tuber-moth infestation has proved the correctness of 
their recommendations. 
Through the kindness of Mr. S. S. Rogers, of the University of Cali- 
fornia, the writer was enabled to compare the results of different cul- 
tural methods. The test field, situated near Van Nuts, Cal., had 
every conceivable variation in culture. Planting depth varied from 
2 to 16 inches. Each plat contained both flat and ridged culture and 
was harvested in three parts, so that each variation in culture had 
early, medium, and late harvesting. 
The results may be briefly summarized as follows : 
Taking the entire field as an average, the percentage of infestation 
in the plats having ridged culture was 8 per cent less than in those 
having flat culture. 
In the same way the plats harvested early had 4 per cent less infes- 
tation than those harvested at the medium period and 9 per cent less 
than those harvested late. 
In the experiments with depth of planting results were even more 
striking. In the plats planted 2 inches deep (many tubers were ex- 
posed) the vines were dead, and the percentage of infestation of the 
tubers varied from 98 to 100. From this the percentage of infestation 
became steadily less, as the depth of planting was increased, until at 
a depth of 6 inches a mi ni mum was reached, several plats giving 
entirely clean potatoes and the average of infestation being low. In 
the plats where deeper planting was used, the potatoes seemed to grow 
as near the surface as where 5 to 6 inches planting depth was used, 
and consequently there was no difference in freedom from the moth. 
Results from the experiments as to time of planting varied so 
greatly that it was evident several other factors have more to do 
with determining infestation than the time of planting. The same 
might be said of the variety test, except that the tubers of varieties 
where the vine stayed green the longest suffered least from the 
moth, 
