Fighting Pests with Insect Allies 



dark-coloured creature which has thrived in the 

 California climate, especially near the sea 

 and in the damp air of those regions has suc- 

 cessfully held the Mack scale in check. It was 

 found, however, that back from the seacoast 

 this insect did not seem to thrive with the 

 same vigor, and the black scale held its own. 

 Then a spirited controversy sprung up among the 

 olive-growers, those near 

 the seacoast contending 

 that the Rhizobius was 

 a perfect remedy for the 

 scale, while those inland 

 insisted that it was 

 worthless. A few years 

 later it was ' discovered 

 that this olive enemy 

 in South Europe is killed 

 by a little caterpillar, 

 which burrows through 

 scale after scale, eating 

 out their contents, and 



an effort was made to introduce the cater- 

 pillar into California, but these efforts failed. 

 Within the past two years it has been found 

 that a small parasitic fly exists in South 

 Africa which lays its eggs in the same Mack 

 scale, and its grub-like larvae eat out the bodies 

 of the scales and destroy them. The climate of 

 the region in which this parasite exists is dry 

 through a large part of the year, and therefore 

 this little parasitic fly, known as Scittcllistd, 

 129 



Rhizobius, t1 

 enemy of the Black Scale 

 of the Olive. 



