THE CHALCIS-FLY IN ALFALFA SEED. 7 
2. The earliest pods have an especially large percentage of the 
seeds infested with chalcis-fly larvee. 
3. The chalcis-fly larvee are able to pass completely through the 
first generation in the earliest pods before the regular seed fields 
are sufficiently advanced for oviposition. 
This cutting should be done with the harvesting of each hay crop, 
before the seed crop is grown. 
It is sometimes necessary to have two or more irrigation ditches 
running parallel, making it impracticable to cut the alfalfa between 
them. In such cases it is economy to fence the ditches and use this 
Fig. 7.—The rank growth of dry alfalfa shown on this ditch bank was loaded with infested seed pods in 
which a multitude.of chalcis-fly larvee were hibernating. (Original.) 
land as a small summer pasture, thus preventing the development of 
alfalfa seed pods and the chalcis-flies. 
WINTER CULTIVATION. 
In the process of harvesting the seed crop many pods containing 
infested seeds fall to the ground. Here they remain until the follow- 
ing spring when the hibernating insects emerge. A thorough culti- 
vation with an alfalfa cultivator, at some time late in the fall or 
in early winter, will sufficiently cover such pods and will prevent 
the emergence of most of the adults when the warm spring weather 
arrives. 
DESTROYING THE SCREENINGS. 
After the alfalfa is thrashed the great mass of screenings which is 
left (see fig. 8) frequently contains large numbers of seeds infested 
with hibernating larve. If the chaff, together with the screenings, is 
placed in a compost pile for three or four months, so that it will 
