254 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 14 



and spray. For surface tension I use the drop-weight method, based 

 upon the weight of a certain number of drops. A definite volume of 

 a standard liquid of known surface tension is run through the appara- 

 tus and the ntmiber of drops determined. This number is compared 

 with the number of drops of the imknown liquid when the surface of 

 the unknown may be calculated by a simple formula. In the case of 

 such substances as casein, etc., it is almost impossible to measure be- 

 cause of the low speed at which the molecules of the casein are adsorbed 

 on the surface, so that you have to allow something like one-half hour 

 to an hour for each drop before it breaks from the tip of the apparatus. 

 What we are interested in is not the static surface tension but the dy- 

 namic surface tension which is the one at the moment of spraying. I 

 think that there is no doubt that we produced a film on the leaf which 

 rolls together into a drop. What we are interested in is maintaining 

 the film already produced. 



Mr. R. L. Webster: I would like to ask whether there is a differ- 

 ence in the surface tension of soft and hard soap, for instance, oleate 

 and potassium? 



Mr. William Moore: I suspect that the oleate would have the 

 lowest. I think there would be a difference between the oleate and 

 the stearate. The oleate soap would probably have a lower surface 

 tension than the stearate soap, although I cannot give you any figures. 



President Wilmon Newell: The next paper is 



ECOLOGICAL OBSERVATIONS ON THE HEMIPTERA OF THE 

 CRANBERRY LAKE REGION OF THE ADIRONDACKS 



By Herbert Osborn, Columbus, Ohio and C. J. Drake, Syracuse, N. Y. 



(Withdrawn for publication elsewhere) 



President Wilmon Newell: We will now hear the paper by Mr. 

 Swezey. 



SOME RECENT INSECT IMMIGRANTS IN THE HAWAILAN 



ISLANDS 



By O. H. Swezey, Experimental Station, H. S. P. A. Honolulu, Hawaii 



It is the prevailing opinion that the endemic insect fauna of the Ha- 

 waiian Islands has developed from ancestral forms which arrived as 

 chance immigrants from elsewhere. Many of these immigrants ar- 



