INSECTS AND OTHER ANIMAL Pxsts INJURIOUS TO FIELD BEANS 975 
this spot were infested with maggots, tho in other parts of the garden there 
was no injury. 
Whelan (1916) has found maggots in fresh manure, and he says: 
Furthermore, it appears that while beans were apt to suffer when planted on freshly turned 
clover sod, especially if recently fertilized with undecomposed manure, they stood a much 
better chance of escape if the field was prepared early in the season and the maggots given a 
chance to develop and disappear before the beans were planted. 
Tho the writer has been unable to find evidence of flies breeding in manure, 
he has found many maggot-infested fields which had been covered with 
manure just before plowing. It must be said, however, that serious out- 
breaks have been found where manure was not used. 
If a field is fitted early and is allowed to dry out before the mature flies 
seek places to oviposit, it appears to be less attractive for oviposition than 
newly turned soil. In 1920 the laboratory field was plowed at a time 
when flies with well-developed eggs were numerous, and many bean seed- 
lings were infested. Fields near by that were plowed earlier and allowed 
to stand were free from maggots. 
Relation of depth of planting to injury by maggots 
Beans planted deep in the ground take longer to reach the surface and 
are thus exposed for a longer period of time to maggot attack. It has 
been observed many times that beans planted deep in wet ground suffer 
more from Hylemyza cilicrura than those that are planted less deep. For 
example, in 1917 it was often noticed that the headlands yielded better 
beans than the remainder of a field. This is attributed to the more shal- 
low planting, for the soil was not so loose at the edges of the field and 
therefore the drill did not sink so deep. 
In 1917 a field under observation had nearly every bean attacked by 
maggots. The seed had been planted in wet soil at a depth of from three 
to five inches. After this first planting was destroyed by maggots, the 
field was reseeded at once, and the beans were dropped as near the surface 
of the ground as possible. Some of the seed was even left on top of the 
soil, and a boy with a, hoe followed the machine to cover the beans left 
exposed. A 95-per-cent stand resulted. 
In another case a grower started to make a very shallow planting of 
beans. When he had gone part of the way across the field, he decided 
that he was not getting the seed in deep enough, and so he planted the 
remainder of the seed much deeper. At harvest time the beans planted 
first, the shallow-planted ones, were the only ones worth harvesting. If 
the beans are planted too deep, many will decay because of the excessive 
moisture, and the maggots will destroy a large proportion of the remainder 
Experiments were conducted in 1917 to test the effect of the depth of 
planting on the time required for the beans to break thru the soil. Beans 
were planted on good, tho very wet, soil on July 12. When the field was 
