71 



appear that it is not an entirely parallel problem to introduce a certain insect 

 which thrives and increases in a new home, and, also, to colonise its controlling 

 enemies. Predaceous enemies and parasites can only thrive and increase as 

 long as they have an abundant supply of the insects upon which they feed, 

 because as soon as they have reduced the numbers of their hosts, so that they 

 do not injure our crops, they have also brought down their own food supply, 

 and to that extent have contributed to their own extinction." Further on, 

 he says : " Parasites not as efficient as Spraying. Where substantially clean 

 fruit must be had, as for snipping and export purposes, spraying, or some 

 other direct means of control, must be practised ; and now that an inexpensive 

 tree-wash for the San Jose scale has been discovered, it is very much to the 

 advantage of everyone to spray regulaily, rather than trust to control by 

 natural enemies." 



In a paper, " Scale Insects and their Enemies in California," contributed 

 by Professor J. B. Smith, State Entomologist in New Jersey (Bulletin 6, 

 United States Department of 'Agriculture, 1896), he makes the following 

 statements, that are now more or less endorsed by Mr. S. A. Pease, in his 

 paper, " Parasites and the State Insectary," in the Official Report of the 

 Thirty-fourth Fruitgrowers Convention, California, 1908: "As to the 

 predaceous insects introduced from Australia, their importance in California 

 has been-grossly exaggerated. Up to the present time they have not estab- 

 lished 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 of these insects is reliable. Whenever any decrease of black scale is 

 observed, and there is any Rhizobius ventralis about, this insect is 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 

 xentralis. No reliable observations have been made, and a very large pro- 

 portion of what is asserted is guesswork. Rhizobius debilis, about which so 

 much has been published, and for which so much has been claimed, was not 

 found in California, and there is every reason to believe that the insect has 

 died out entirely. In most cases the common Californian Scymnus margini- 

 collis is mistaken for Rhizobius debilis, and sometimes for lophantce as well. 

 RJiyzobius debilis does not occur in any of the collections in California except 



In imported specimens Perhaps Orcus chalybeus should be 



referred to here, because that is still to be found in small numbers in one 

 orchard not far from Los Angeles. It has not increased, however, since the 

 first year or two, and, on the contrary, seems rather to be d^ing out, just 

 as 0. autralasire did two years previously. Taking everything into con- 

 sideration, there is nothing that warrants the assertions put forth by the 

 horticulturists of California." 



" There is no doubt that the native parasites of scale insects are efficient 

 in keeping down the insects to some extent ; but of the sixty species imported 

 by Koebele, in many thousands of specimens there is not one that can be con- 

 sidered a success at the present time. Of course, there is a belief to the 

 <contrary, and some superficial evidence to support it ; but there is, at least, 

 as much evidence in the opposite direction, and it seems to me that the state 

 of affairs hardly warrants the discontinuance of destructive measures against 

 the injurious insects." 



S. A. Pease, of San Bernardino, in his interesting paper previously quoted, 

 read before the Thirty-fourth Fruit-growers' Convention of California, last 

 May, says : " Since 1893, we have had periodical reports that a perfect 



