This species is also preyed upon by another bug, Aril us eristatus 

 L., the Avheel bug, which tlie writer has frequently seen attacking the 

 young harlequins. 



The influence of natural elements, particularly cold winters, has 

 already been mentioned as a means of decimating this pest. It is well 

 to add, however, that the writer had this species under close obser- 

 vation in 1899, and that as a result of sudden cold snaps, 85 per cent 

 of the bugs in fields near Washington in that year had been killed by 

 January 15, 1900. 



METHODS OF CONTROL. 



The experience of years has shown that in order to obtain the best 

 results in the treatment of the harlequin cabbage bug preventives are 

 necessary, as there is great difficult}^ in obtaining insecticides wdiich 

 are effective and which do not at the same time injure or kill the 

 plants. These preventives are: (1) Clean cultural methods, espe- 

 cially in the fall ; (2) the use of trap crops of mustard or other plants 

 in the spring, and (3) hand methods. With strict observance of clean 

 farming few of the insects will survive the following spring and the 

 adoption of trap crops leaves fewer still to be destroyed by mechanical 

 measures. In some cases all three methods should be adopted, for if 

 they are neglected the grower will find it a most vexatious matter to 

 control the pest in the midst of the growing season. 



Clean cultural methods. — Of prime importance are clean cultural 

 methods. The value of clean methods of farming has been recognized 

 by nearly everyone who has had experience with this insect. The 

 practice of leaving stalks of cabbage and other cruciferous plants in 

 the field late in the autumn and in the early winter, or of permitting 

 rank weeds to grow up, or, in fact, allowing any sort of debris to accu- 

 mulate, serves as a means of protracting the life of this insect, as all 

 such material either affords it food late in the season or quarters for 

 protection against the elements during winter. It is even inad- 

 visable to plant crucifers in the vicinity of outhouses and barns, as 

 the bugs are apt to enter these latter for passing the winter. 



Throughout the year wild plants of the mustard family, on which 

 the insect chiefly breeds, should be carefully kept down not only in 

 the fields but in the immediate neighborhood. A list of such plants is 

 given on page G. 



Trap crops. — Some plants, such as cabbage, turnip, or kale, may be 

 planted late, to be left at intervals throughout infested fields. These 

 trap plants attract the insects in the fall, and here the latter may be 

 killed with pure kerosene, or by mechanical methods. Where it is con- 

 venient to leave piles of rubbish until the insects are attracted to 

 them this may be done, and the entire material, insects and all, should 

 then be burned. 



[Cir. 103] 



