298 INSECTS AND MAN 



from one country to another, for the benefit of mankind, 

 forms one of the romances of applied entomology. As the 

 Americans were the pioneers in this work, it is to their 

 country that we will turn for our examples. 



The practice of the control of insect pests by their 

 natural enemies is one of modern times, for the earliest 

 record of the work, on anything approaching a commercial 

 scale, dates back but twenty-five years. It is based on the 

 assumption that all nature is in a state of equilibrium, that 

 is to say, that all life, in its native home, is kept in check 

 by other forms of life which prey upon it. 



For many years the orange and lemon groves of 

 California were threatened with ruin, owing to the depre- 

 dations of a relatively large scale insect known as the 

 fluted or cottony cushion scale, Icerya purchasi. A con- 

 siderable amount of research showed that in all probability 

 this noxious insect had been introduced into the United 

 States from Australia in 1868. It was found in Portugal 

 in 1873, near Naples in 1900, and has been subsequently 

 met with in Egypt, Syria, Greece, Dalmatia, Sicily, and 

 France in 1910. All mechanical means of control having 

 failed, in 1889 Professor C. V. Riley, chief of the American 

 Bureau of Entomology, sent Mr Albert Koebele to the 

 Antipodes to try and discover what insect, if any, kept 

 the cottony cushion scale in check in its native land. His 

 voyage of discovery was eminently satisfactory, for he 

 found that the scale insect was rendered almost harmless 

 in Australia, because, whenever and wherever it appeared, 

 it was eagerly devoured by a small ladybird, known to 

 science as Novius cardinalis. This little beetle was 

 accordingly transported to California, where, fortunately 

 for the citrus growers, it flourished and multiplied from 

 the day of its introduction, and, as a consequence, the 

 cottony cushion scale is now no longer a serious factor in 

 the citrus production of California. But, to this day, large 

 numbers of the ladybird are reared annually at Sacramento, 



