The movement of weevils in a mass of grain was investigated using metal pipes 4 ins. in diameter. These grain columns were broken down into samples. It was found that the predominant movement of weevils was towards the bottom.

The major factor affecting movement was tightness of packing but although tight packing restricts movement it does not prevent oviposition. Small insects move more easily in grain than bigger ones and also show a greater tendency to move downwards. Increase of moisture content which increases the amount of airspace also increases the ease of insect movement.

The results of experiments giving the weevils a choice of moisture content were somewhat contradictory. This is partly due to the choice of the weevil being affected by the humidity it experienced prior to the test and partly due to the moisture choice being overridden by the greater attraction of the end of the grain column. On the whole, however, damper grain appears to be preferred to dry grain.

In the field, owing to the tighter packing, movement is likely to be more restricted than in these experiments. The tight packing will prevent much of the downward penetration of weevils observed in these experiments but some such movement may occur on the walls and posts. Where insects are originally placed in the centre of a bulk of grain they will often be immobile but will lay eggs and be liable to cause heating. It is clear that the insects will tend to move toward the edges of the bulk and remain there.