February, '17] GROSSMAN: COLONIZING PARASITES 177 



Noctuid larvae were not more definitely determined. These cater- 

 pillars are very small, being in the first stage and after having had a 

 tanglefoot bath, it was impossible to determine them more definitely. 



Mr. J. W. McCoLLOCH : What size of mesh was used in the screens. 



Mr. C. W. Collins: We used f-inch mesh, also f-inch, but did 

 not use the two sizes under exactly the same conditions. 



Mr. J. W. McColloch: Is this cloth wire or poultry wire? 



Mr. C. W. Collins: Poultry wire. 



Mr. E. D. Ball: This paper opens up a very definite field for work. 

 An observation I made this winter leads me to believe that I found 

 San Jose scale infestation which had been wind borne three or four 

 blocks, and that a single infested tree had apparently been the source 

 of the infestation. I wonder if any of this work has been done on scale 

 insects. 



Mr. C. W. Collins: We have not done any. Professor Quayle 

 has carried on some interesting experiments on black scale in California. 

 He succeeded in taking them 450 feet from infested orchards and he 

 has taken red scale 150 feet from an infestation. 



President C. Gordon Hewitt: I will now call on Mr. Crossman 

 to present his paper. 



SOME METHODS OF COLONIZING IMPORTED PARASITES 

 AND DETERMINING THEIR INCREASE AND SPREAD 



By S. S. Grossman, Entomological Assistant, Bureau of Entomology, U. S. D. A. 



The control of phytophagous insects by means of entomophagous 

 ones may be divided into two classes: first, the control of native insects 

 by native parasites; second, the control by importations of parasites 

 and predaceous enemies of injurious insects which have become es- 

 tablished in a new land. In the United States at least one half of the 

 injurious insects of economic importance are of exotic origin and have 

 become established in this country, because they are unhampered by 

 many of the factors that hold them in check in their native lands. Dr. 

 C. V. Riley, while entomologist to the United States Department of 

 Agriculture, was the first to introduce successfully into this country a 

 parasite of an insect of exotic origin. In 1883^ he succeeded in estab- 

 lishing Apanteles glomeratus L. which is a parasite of Pontia rapce L. 

 Six years later Novius cardinalis was introduced into California. 



Since Riley's successful introduction of A. glomeratus, many impor- 

 tations of beneficial insects have been made and the future undoubtedly 



1 Popular Science Monthly, vol, LXXII, pp. 363, April, 1908. 



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