Chrysomelidae 477 



METHOD OF REARING DIABROTICA 



DUODECIMPUNCTATA, THE SOUTHERN 



CORN ROOT WORM 



D. L. Wray, North Carolina State College 



AFTER collecting the adults in the field each pair is placed for egg 

 l laying in a 4-ounce tin salve box with a piece of slightly moist blot- 

 ting paper covering the entire bottom. Small sections of very young corn 

 stems, or clover leaves, or leaves of other food plants are put in the 

 boxes with the beetles. The female will lay her eggs in the moist spot of 

 the blotting paper in most cases. However, some eggs are laid on the 

 under side of the clover leaves or on the cornstalk. The food should 

 be watched carefully and changed daily if egg laying records are to be 

 kept. The moisture in the blotting paper should be kept at a minimum. 



The eggs may be removed from the blotting paper by means of a 

 moistened camel's hair brush and transferred to an incubation cage 

 which consists of a % ounce tin salve box lined with a moist piece of 

 blotting paper. The moisture content must be carefully watched as too 

 much water will cause molds to develop and too little will cause desicca- 

 tion of the eggs. The happy medium must be judged by the surrounding 

 temperature and humidity. 



After the eggs hatch the young larvae may be transferred to a 4-ounce 

 tin salve box on the bottom of which is a thin layer of coarse sand 

 covered by a piece of blotting paper. On the paper are placed the 

 small sections of very young, tender cornstalk, in which the larva will 

 begin eating out a cavity; or else the larva may be placed in a small 

 cavity dug out with a scalpel to accommodate it. For food for young 

 larvae it is best to keep on hand several small plats of seedling corn in 

 order to have sufficient tender food. They may be planted at weekly 

 intervals. When the larvae become older, very young cornstalks may 

 be obtained from the field. The food must be kept fresh and will need 

 to be changed every 3 or 4 days. 



After the last larval molt the larva and its food (generally it is inside 

 the section of cornstalk at this time) may be transferred to a jelly glass 

 or small-sized battery jar, the bottom of which is covered with about 

 1% inches of soil, preferably loam. The larva and its food is placed on 

 this and a cheesecloth cover put on. The soil in the jelly glass should 

 be just barely moist. It is well to have small pieces of blotting paper 

 directly under the food if the soil is too wet. The larva will generally 

 go into the soil to pupate or may form a pupal cell in the section of 

 cornstalk. The moisture content must be watched carefully in order to 

 get the best percentage of emerging adults. These adults may then be 

 used for egg laying if successive generations are to be reared. 



