io8 AN ECONOMIC ENTOMOLOGY. 



permanence. Aniline dyes and colors are superseding it, how- 

 ever, because of their cheapness and the greater ease with which 

 they may be obtained. 



Mealy bugs are easily destroyed by contact poisons, almost 

 any soapy solution killing them readily. A very dilute kerosene 

 emulsion answers every purpose, and even a weak salty solution 

 is satisfactory. I have used both kainit and muriate of potash 

 dissolved in water at the rate of an ounce in a quart, and it has 

 been perfectly effective where entire plants have been dipped into 

 it. A tobacco decoction, one pound in one gallon of water, is 

 also useful, and not dangerous to the most delicate plants. Where 

 house-plants are troubled the tobacco water is very convenient, 

 or common insect-powder may be used at the rate of an ounce 

 in two quarts of water, and sprayed on with an atomizer. Where 

 applications are to be made on a large scale, the diluted kerosene 

 emulsion is the most satisfactory, one part in fifteen ot water be- 

 ing ordinarily sufficient. 



Next comes a series where the excretions are in the form ot 

 waxy scales, which sometimes become hard, brittle, and beauti- 

 fully ribbed. The female forms a sort of sac of these waxy scales, 

 and in it the eggs, mixed with a very fine powder, are contained. 

 This type is also rather more common southwardly or in warm 

 countries, the few species that occur in the North being rather 

 scarce and generally confined to weeds. The " cottony cushion 

 scale," Icerya piirchasi, which has caused such injury in Cali- 

 fornia, belongs here, and we have several allied species in Florida, 

 and yet more in the West Indies. All these insects gain their 

 food by sucking the plant juices, and their power of injury is 

 magnified by their enormous productiveness. 



Perhaps this is a good place to speak somewhat at length on 

 this " cottony cushion scale," and the measures taken against it 

 by introducing foreign predaceous species. The very remarkable 

 success that has attended the introduction of "lady-birds" 

 (Coccinellidae) from Australia has led many persons to the belief 

 that insects of similar character might be introduced from other 

 countries to deal with some of our native species, and much 

 time has been wasted and some money spent by ill-considered 

 schemes of this description. The factors that caused success in 

 the case of the Icerya were : ist, an Insect introduced from a 



