115 



watering hose will be sufficient to entirely replace the spray pump. 

 The arsenites may be used in the same way as kerosene, using a 

 mixture stronger than the standard and allowing it to be diluted in pass- 

 ing through the nozzle. A stopcock on the inlet tube will graduate 

 thei)roportions, as with kerosene. Perhaps an apology is due the Asso- 

 ciation for presenting this suggestion before I have actually proved its 

 utility. I am now having nozzles made for experiment, and will be 

 able to give a definite report later. 



Mr. Smith asked if others had had experience with the combination 

 pump which was being put on the market by the Deming Company, 

 and said that his experience with it had not been satisfactory. 



Mr. Marlatt said that in his paper, which was to follow, some experi- 

 ments with this pump were detailed which would answer the question 

 of Mr. Smith. 



Mr. Marlatt then read the following paper: 



NOTES ON INSECTICIDES. 



By C. L. Marlatt, WaHhington, D. C. 



So much has been written about insecticides in the publications of the 

 various experiment stations and those of our Entomological Division at 

 Washington, and they have'so frequently been a subject of discussion 

 at the meetings of this Society, that one might infer that enough experi- 

 ence had been accumulated and information gained to enable us to 

 arrive at definite conclusions in the use of the more important insecti- 

 cides against the leading injurious insects. It must, however, be 

 strongly impressed on every member of the Society who is engaged to 

 any extent in personal experimentation and actual field operations 

 against insects that the subject is still far from being exhausted, and 

 that every season's experience develops a host of new facts and 

 methods of greater or less value. It is not sufficient to know that ker- 

 osene emulsion or resin wash will destroy certain classes of insects or 

 insects in certain stages of development, and that they are not gener- 

 ally injurious to foliage, but it is necessary to know also the minute 

 particulars of time, weather conditions, and conditions of the insect 

 which will most conduce to successful treatment. As an illustration 

 of this, the various scale insects which have always been leading pests 

 in subtropical regions, and are rapidly gaining importance also in the 

 north, are, generally speaking, invulnerable to insecticide action in any 

 strength which may be safely applied during the growing season after 

 the covering scales are once well formed; and these insects can, there- 

 fore, only be successfully treated immediately after the young are dis- 

 closed. The farmer or fruit-grower, without the aid of a hand lens, can 

 521G— No. 2 5 



