. Circular. Insects. 8 the aphides so that few are left to hibernate and produce other gen- erations of the pest the following year. The value of these natural enemies against aphides is such that entomologists frequently advise the employment of remedies only 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 remedy, for the reason that, while aphides are all destroyed, a considerable proportion of the
. Circular. Insects. 8 the aphides so that few are left to hibernate and produce other gen- erations of the pest the following year. The value of these natural enemies against aphides is such that entomologists frequently advise the employment of remedies only 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 remedy, for the reason that, while aphides are all destroyed, a considerable proportion of the ladybirds and other hardy beneficial insects, which are practically always present on the infested vines, survive this 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 entirely prevented if the employment of methods for its con- trol were begun upon the insectfs first appearance. 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 lower surface of the leaves be examined. All things considered, the most satisfactory wa}r of controlling this insect is by fumigation. As an aid, however, cultural methods are necessary. In the South spraying with kerosene and other emulsions is preferred to the bisulfid of carbon method, and tobacco
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