8 



the aphides so that few are left to hibernate and produce other gen- 

 erations of the pest the following- 3^ear. 



The value of these natural enemies against aphides is such that 

 entomologists frequently advise the employment of remedies onl}^ 

 when the enemies are not present in abundance. The possible utiliza- 

 tion of natural enemies in the field will be considered on pages 15 and 

 16 of this circular. In tobacco fumigation, which will -presently be 

 considered, we have an almost ideal remed}^ for the reason that, while 

 aphides are all destro3^ed, a considerable- proportion of the ladybirds 

 and other hardy beneficial insects, which are practicallj^ always present 

 on the infested vines, survive this treatment. 



Fig. 4. — A syrphus-fly {Syrphus ribesii): a, fly; b, lateral view of head; c, larva or active immature 

 form; d, anal spiracles; e. thoracic spiracle of same. All much enlarged (original). 



METHODS OF CONTROL. 



The severe losses occasioned by the melon aphis in its seasons of 

 greatest destructiveness could be largely mitigated and in many cases 

 almost entirel}^ prevented if the employment of methods for its con- 

 trol were begun uj?o?i the insecfs first apj^ecirance. For its successful 

 treatment it is necessary to keep constantly in mind several of the 

 facts that have already been given more in detail. In ordinary sea- 

 sons the species is controlled by the combined operation of natural 

 elements and insect enemies, but at times when the weather is unfa- 

 vorable to the development of these enemies the grower should be on 

 the alert. The presence of the aphides is often not detected until they 

 are numerous, and even then they are not apt to be noticed unless the 

 loirer surface of the leaves be examined. 



All things considered, the most satisfactory way of controlling this 

 insect is b}^ fumigation. As an aid, however, cultural methods are 

 necessary. In the kSouth spraying with kerosene and other emulsions 

 is preferred to the bisulfid of carbon method, and tobacco is now much 

 used, especially in Texas. The encouragement of natural enemies 

 gives promise of success. 



I 



