47 



mixture are used by a single farmer. The process is expensive, of course, 

 but the results arc good, and without it the orchards would be valueless. 

 It is claimed that especially on peach the lime, sulphur, and salt mix- 

 ture acts as a fungicide, and prevents leaf curl, while apparently 

 strengthening the tree and enabling it to better retain the set of fruit. 

 In the immediate vicinity of San Francisco and south of that point, 

 natural causes have resulted in keeping the pernicious scale in check. 

 In the first place the scale has the appearance of becoming worn out; 

 that is to say, there are a great many dead specimens to be found on 

 the trees — the young themselves, when moving about, appear as if they 

 were only half alive — and altogether it seems as if there was some force 

 at work that is weakening the insect. It is also preyed upon by Chilo- 

 corns bivulnerus in all its stages, and infested by Aphelhius Juscipennis, 

 both of which are also found in the Eastern States. These two insects 

 breed through almost the entire year. The Aphelinus probably con- 

 tinues throughout the entire season, while the Chilocorus has probably 

 only a very short resting period in midwinter and another perhaps 

 somewhat longer in midsummer. The scale has quite a long period of 

 rest, and does not begin breeding in spring until May. The result is 

 that the predaceous and parasitic enemies have a distinct advantage 

 over the scale and are able to keep it down to harmless numbers. None 

 of the insects introduced from Australia which have been credited with 

 controlling the scale ever had any effect upon it whatever. AVith the 

 possible exception of Rhizobius lophantce none of them were introduced 

 into California until the scale in the southern part of the State had 

 spent its force, and furthermore, lophantce, the only species which has 

 been found feeding upon the insects at all, does not become numerous 

 until well along in the summer, and has besides no great partiality for 

 orchards. It is found as frequently in the canyons as it is on cultivated 

 lands. As to the predaceous insects introduced from Australia, their 

 importance in California has been grossly exaggerated. Up to the 

 present time they have not established themselves permanently in 

 more than two counties in the State, and in regions where thousands 

 and tens of thousands have been introduced they have died out almost 

 completely. Very little of the evidence that is given as to the work 

 done by these insects is reliable. Whenever any decrease of black 

 scale is observed, and there is any Rhizobius ventraiis about, this insect 

 is credited with the work done, hi a number of instances where trees 

 were said to have been cleared by this insect, or rather the scale 

 destroyed, it was found that while the scales were dead there was no 

 sign of an injury such as would have been made by feeding upon it by 

 either the larva or adult of Rhizobius ventraiis. No reliable observa- 

 tions have been made, and a very large proportion of what is asserted 

 is guesswork. Rhizobius debilis, about which so much has been pub- 

 lished, and for which so much has been claimed, was not found in Cali- 

 fornia at all, and there is every reason to believe that the insect hns 



