BENEFICIAL INSECTS PREDACEOUS. 259 



longer on the trees without evaporating. Eleven to one is the 

 strongest it can be used with safety on citrus trees. 



This remedy is used by Mr. NefF, Superintendent of the Win- 

 dermere Orchards at La Mirada, but he uses twenty pounds 

 more whale-oil soap, on account of lime in the water at that 

 place. On this account it requires nearly an hour to prepare a 

 perfect emulsion. He also uses warm water to add to the stock 

 solution, as it works better than cold water. Mr. Neff says: 

 " Some distillates will kill very large 'black scale,' while another 

 lot of distillates, apparently the same, does not kill any scales 

 larger than a pinhead." 



BENEFICIAL INSECTS-PREDACEOUS. 



In no part of the world has the value of predaceous and 

 parasitical insects been more fully demonstrated than in this 

 State. The cottony cushion scale (Icerya purchasi, Maskell) 

 had gained a very strong foothold here, especially on citrus 

 trees, and the damage done by its ravages can hardly be esti- 

 mated. Everywhere was noted its resistless and ruthless 

 march. Watchfulness did not guard against its spread. The 

 most heroic treatments proved of no avail. But in the deep 

 night of our despair there came to our relief a minute ladybird, 

 the Vedalia cardinalis, which in less than a year entirely freed 

 the orchards of California of that pest, thereby accomplishing 

 a work entirely unprecedented in the annals of economic 

 entomology. In 1892 another ladybird, Novius Koebelei (see 

 Plate XXVI), also a foe to this scale, was introduced, although 

 a repetition of the work achieved by the Vedalia was gravely 

 doubted. What energy, science, and money could not perform 

 in years, these minute creatures accomplished in a short period 

 of time, and to those who closely watched their work it seems 

 almost incomprehensible. 



These friendly foes are assisted materially by other species, 

 and especially by internal parasites. That other insects with 

 similar instincts could ever be discovered was doubted, but 

 through persistence and faith on the part of the State Board 

 of Horticulture, a further search was instituted, which was 

 rewarded by the discovery of two other species. One, the 

 Rhizobius ventralis (see Plate XXVI), is an effective foe of the 

 black scale (Lecanium olex'), which it is diminishing very 



