THE CHALCIS-FLY IN ALFALFA SEED. 5 
estimate with any degree of accuracy without the aid of a good 
microscope. 
Alfalfa seed pods collected in different localities from both early 
and late crops show that seed crops maturing late in the season 
suffer a greater loss from this insect than those maturing early. 
Observations showed that the early emerging adults are crowded 
to the first seed pods in large numbers, resulting in a heavy infes- 
tation. These first pods are, however, nearly always found on the 
isolated plants growingeon fence lines and ditch banks. 
In localities where bur clover is abundant the pods of these plants 
receive the early infestation. 
When the alfalfa pods develop in large numbers on the early 
seed fields there is apparently a decrease in the percentage of in- 
Fig. 5.—A severely infested alfalfa seed field which had been abandoned. Infested pods cover the ground, 
where they offer favorable conditions for the hibernation of the chalcis-fly. (Original.) 
fested seed, and from this time on a gradually increased infestation 
follows until the close of the season. 
Seed pods collected in different localities and subjected to exami- 
nation with a microscope show that the chalcis-fly destroys from 
10 to 30eper cent of the seeds in the early crops and from 20 to 70 
per cent of the seeds in the late crops. Several samples were exam- 
ined which showed that 85 per cent of the seed had been destroyed 
by this insect. . 
The actual loss per acre depends upon the market value of the 
seed and upon the yield per acre of the crop. The loss has been 
observed on different farms to vary from $5 to $60 per acre. There 
are still many seed-growing districts which have not been visited in 
connection with this study and where little is known concerning the 
work of the chalcis-fly. 
67214°—Bull. 636—14 
9 
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