ENTOMOLOGY 371. 



peas, etc., which have their leaves covered with a waxy secretion 

 which prevents water from lying upon them. Any kind of soap will 

 answer for this purpose, and it may be remembered that one quart 

 of soft soap is about equal to one pound of hard soap. Another 

 method for making home-made fish-oil soap is given by Van Slyke 

 and Urner, and is as follows : 



Formula for Making Forty Pounds of Fish-Oil Soap. 



Caustic soda 6 pounds. 



Water l 1 /^ gallons. 



Fish-oil 22 pounds. 



The caustic soda is completely dissolved in the given amount of 

 water and the fish-oil is added gradually under constant and vigor- 

 ous stirring. The combination occurs readily at ordinary summer 

 temperatures and the operation is soon completed. The mixing may 

 be done in any receptacle sufficiently large to contain the whole 

 amount of material. It would probably not be desirable to attempt 

 to make more than 20 to 40 pounds at a time, since the difficulty of 

 thoroughly stirring a larger mass would tend to make a complete 

 combination less sure, thus rendering liable the presence of too much 

 free alkali. Complete and thorough stirring is essential to success. 

 Caustic soda should be handled with precaution, since in concentrated 

 form it easily injures the skin. The authors show that when caustic 

 soda can be got for 4% cents per pound and the fish-oil at 29 cents 

 per gallon, the material for 40 pounds of soap costs $1.14, or 2.85 

 cents per pound. (Bui. 154, Ontario Agr. Dep.) 



Pyrethrum, or Insect Powder. This insecticide is sold under 

 the names of Buhach, Dalmatian, and Persian insect powder, or sim- 

 ply insect powder, and is the ground-up flowers of the Pyrethrum 

 plant. It acts on insects externally through their breathing pores, 

 and is fatal to many forms both of biting and sucking insects. It is 

 not poisonous to man or the higher animals, and hence may be used 

 where poisons would be objectionable. Its chief value is against 

 household pests, such as roaches, flies, and ants, and in greenhouses, 

 conservatories, and small gardens, where the use of arsenical poisons 

 would be inadvisable. 



It is used as a dry powder, pure or mixed with flour, in which 

 form it may be puffed about rooms or over plants. On the latter it 

 is preferably applied in the evening, so as to be retained by the dew. 

 To keep out mosquitoes, and also to kill them, burning the powder 

 in a tent or room will give satisfactory results. 



It may also be used as a spray at the rate of 1 ounce to 2 gallons 

 of water, but in this case should be mixed some twenty-four hours 

 before being applied. For immediate use, a decoction may be pre- 

 pared by boiling in water from five to ten minutes. 



Tobacco Decoction. A tobacco decoction sufficiently strong for 

 aphides and other very delicate insects may be prepared from to- 

 bacco stems and other refuse tobacco by boiling at the rate of 1 

 pound for each 1 or 2 gallons of water, sufficient water being added 

 to make up for that lost in boiling. 



