CONTENTS. 



Page. 



Introduction 71 



Occurrence in Colorado 71 



General appearance and habits . 72 



Life history 73 



Rearing records 73 



Egg-laying record 75 



Natural enemies 75 



Experiments with insecticides 76 



Recommendations for control 76 



Conclusion 76 



ILLUSTRATIONS. 



Page. 

 Fig. 25. The horse-radish webworm (Plutella armoracia): Adult or moth, side 



view and with wings spread 72 



26. The horse-radish webworm: Larva, lateral and dorsal views 72 



27. The horse-radish webworm: Pupa 73 



28. The horse-radish webworm: Cocoon 73 



in 



