INSECTS INJURIOUS TO POTATOES AND TOMATOES 259 



in about six or seven weeks. They are then about a half 

 inch long. The head is dark brown; the first segment is an 

 old rose color, with dark brown shield on the back; the second 

 segment is a similar clouded pink; while the third and succeeding 

 segments are a clouded white, often becoming yellowish or green- 

 ish, according to the food eaten. The full-grown larva re- 

 turns to the mouth of the burrow and there makes its 

 cocoon, or leaves it and forms the cocoon in some depression of 

 the potato or in some crack of the storage vessel or in a fold 

 of the bag. The cocoon is constructed quite differently from 

 that of most moths, as described by Mr. Clarke. The larva first 

 makes a mat of silk and then forms an outer layer to the surface 

 of which particles of dirt and rubbish adhere so that the cocoon 

 is well concealed. When this pocket-like cocoon is finished the 

 larva enters it and closes the open end and in it transforms to 

 the pupa. The pupal stage lasts about two weeks, so that the 

 complete life cycle requires from nine to twelve weeks, there being 

 several generations during the year, according to the temperature. 

 Control. As the insect breeds on various common weeds of 

 the Nightshade family (Solanacew) , it is important that they be 

 destroyed wherever found. Seed potatoes must be free from the 

 larvse, or they will soon give rise to moths which will infest a 

 whole field. When young plants are found wilting, the infested 

 stalks should be cut and destroyed as soon as possible to prevent 

 the further development and spread of the pest. Care should 

 be taken in cultivating to hill up the soil, or thoroughly cover 

 the tubers, so that they are not exposed. After digging, the 

 potatoes should not be left exposed in the field any longer than 

 is absolutely necessary and should not be covered with the tops 

 to shade them, as is often done, as this furnishes a shelter for the 

 moths and induces oviposition upon the tubers. Infested fields 

 should have the stalks and all rubbish and refuse thoroughly 

 raked up and burned as soon as possible, or sheep and hogs may 

 be turned into the fields to destroy the stages which may be 

 left in the vines or in the soil. Where fields have been flooded 

 for two or three weeks after the crop has been dug, they have 

 been entirely freed of the pest. For the treatment of stored 

 potatoes, fumigation with carbon bisulfide in a tight room 

 seems to be the only satisfactory method. This should be done 



