514 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 4 



and chief credit for this is usually given to the beetle. There are 

 cases, however, where for some reason or another, the beetle has not 

 been able to prevent the scale doing very considerable injury to the 

 tree; and there are also cases where the scale is harmless and where 

 there are no beetles. 



The most important Coccinelhd attacking the black scale is Rhizo- 

 hius ventralis Black, which was introduced at the same time as cardinalis. 

 This beetle and its larva feed upon the eggs and younger stages of 

 the scale and while very common has never been seen in large numbers. 

 Another species of the genus, Rhizobius lophanthce Blaisd. is the most 

 important Coccinellid attacking the red, yellow and purple scales 

 in the State. This species was first described from California, but 

 it appears that it was imported along with several others and that it 

 was lost track of for some time. In a grove in San Diego County 

 where the owner was assured his red scale was kept in check by a 

 species of Aphelinus, an examination of 2,000 scales showed that 

 3.3 per cent were attacked by Aphelinus, 2.2 per cent by Aspidioti- 

 phagus and nearly 23 per cent by Rhizobius lophanthce. Greater 

 actual evidence of the work of Coccinellids was shown in this case 

 than any that has come to our notice. Coccinellids and other pre- 

 daceous enemies may, of course, consume many of the young scales 

 and eggs, and of which no evidence remains, but we are here considering 

 only the attacks on the fixed scales. The Coccinellid, Cryptolmmus 

 montrouzeri Muls. another of Koebele's introductions, is the most 

 important species attacking the citrus mealy bug Pseudococcus citri 

 Risso, at the present time. This beetle often appears in large num- 

 bers and sometimes greatly reduces the number of mealy bugs, but 

 the effects of the beetle are too irregular, and the trees are never 

 free from the sooty mold fungus. There are several species of native 

 Coccinellids that may feed on scale insects but these need not be 

 considered here. 



CONCLUSION 



With the exception of the soft brown scale, the cottony cushion 

 scale and probably the mealy bug, the insects mentioned in the fore- 

 going pages are the most serious scale pests attacking citrus and 

 deciduous fruit trees in the State. In the citrus belt of southern 

 California more than half a million dollars are expended annually 

 in fumigating and spraying for the black, red, yellow and purple 

 scales. More fumigation is practiced in proportion to the acreage 

 than ever before. Of the four scales mentioned, the black is probably 

 the most important. Of the scales attacking deciduous trees, the 

 San Jose and Apricot or European Fruit Lecanium are the most 



