THE MARGUERITE FLY. 49 



well follow one week later, as it is highly desirable that the insect be 

 checked to as great a degree as possible at its very start. The spraying 

 should then be continued regularly every eleven or twelve daj^s. A longer 

 interval than twelve days is not advisable, as it is more difficult to kill 

 nearly full-grown or full-grown larvse, and pupse are still more difficult. 

 In spring, when it becomes warmer in the house, — or at any time if the 

 plants are grown at a higher temperature than usual, — the sprayings will 

 probably have to come a little more often. Should one succeed in ex- 

 terminating the insect, spraying might be discontinued after cold weather 

 has set in, for then the danger of the insect's coming into the house is past. 

 With the coming of spring, however, one's vigilance should be renewed, for 

 if the insect is able to pass the winter outside of the greenhouse in a dor- 

 mant state, that is, to hibernate, there is a possibiUty, it may get into 

 the house when it becomes active again. If " Black Leaf 40 " instead of 

 " Nico-Fume" Liquid is used, it should, at first at least, be used at the 4-J^ 

 strength. Later, especially if one should spraj^ regularly, 1 part to 

 about from 430 to 450 parts of water, at which strength Mr. Nicholson 

 uses the "Nico-Fume" Liquid, might verj^ hkely prove effective. 



The importance of thorough sprajang cannot be overemphasized, as 

 the insect multiplies very rapidly under normal conditions. Both surfaces 

 of the leaf should be entireh'- and uniformlj^ covered, as the eggs, lai'vae 

 and pupae may occur in any part of the leaf. Special pains should be taken 

 to hit the lower surfaces of the leaves, as from the lower surfaces will be 

 reached the majority of the eggs and newly hatched larva? — which will 

 thus be cut off at the verj^ beginning of their career of mischief — and 

 full-grow7i larvae and therefore pup^e. As the solution must penetrate 

 into the tissues to do its work, it is important also that it adhere well to 

 the leaves. A nozzle giving a fine spray should therefore be used. Should 

 difficulty for some reason or other be experienced in this respect, the addi- 

 tion of soap might be advisable, — whale-oil soap or good laundry soap, 

 at the rate of 1 pound to about 30 gallons of water. The soap increases 

 the adhesiveness of the spray solution through its own adhesive character, 

 and by lessening the formation cf drops the last property insures a more 

 even and uniform distribution of the solution on the leaf surface as well. 



The soap should be dissolved in water before the "Black Leaf 40" or 

 "Nico-Fume" Liquid is added — the soap cut in thin sHces will easily 

 dissolve in some boiling water. After adding, the solution should be 

 stirred thoroughly to obtain uniformitj^ More material than is needed 

 for one apphcation should not be prepared; in other wordf, the materials 

 should be mixed shortlj' before applying. 



Natural Enemies. 



Spiders. 

 The various spiders occurring in the greenhouse, by preying upon the 

 adult flies, capturing them directly, and indirectly by enmeshing them 

 in their webs, are of aid to the florist in that they reduce the numbers of 



