Studies on Eggs of Apple Plant Lice 39 



results, so far as similar experiments are concerned, agree with 

 those obtained by the author during 1917 and 1918. 



INIisciBLE Oils 



A considerable amount of investigation has been conducted 

 with various kinds of oils, commercial and otherwise, on the eggs 

 of apple aphides. A number of workers have experimented with 

 crude oil emulsions and miscible oils. The most recent work is by 

 P. R. Jones (12), who in a preliminary report treats of various 

 contact insecticides, but deals particularly with diiferent oils as 

 miscible oils, distillate oil emulsion, asphalt emulsion, crude oil 

 emulsion, etc. His general conclusion in respect to these products 

 is that oils having a specific gravity, 14°-29° Baume, are much more 

 etfective in killing the eggs of aphides than high-gravity oils, 

 31°-41° Baume. His recommendation reads, "As far as can be de- 

 termined at present under western conditions it is believed that 

 dormant treatment for eggs of the apple and purple aphides should 

 be either commercial crude oil emulsion, 1-9 or 1-10 (where the 

 concentrate contains 85 per cent crude oil) ; home-made crude oil 

 emulsion, 19°-23° Baume — and the application made as late in the 

 winter as possible before the buds start to show green." He ex- 

 perimented with various miscible oils, some made from low-gravity 

 oils and others from high-gravity oils, and so far as can be learned 

 from his report the above conclusions pertaining to specific gravity 

 of oils in general also hold for miscible oils. His results will be 

 compared with those observed in this study. 



No attempt was made by the author to carry on an extensive 

 investigation with various oils, but two commercial miscible oils 

 which are utilized extensively in New Jersey and other eastern 

 states have been tried in a number of experiments, and their results 

 carefully observed. The trade names for these oils are "Mechling's 

 Scale-Oil", manufactured by Mechling Brothers Manufacturing 

 Company, Camden, N. J., and "Scalecide", manufactured by 

 B. G. Pratt Company, New York City. Both of these oils are 

 largely made from oils which have a comparatively low specific 

 gravity; the specific gravity and the information furnished by the 

 two concerns confirms this statement. The specific gravity of 

 "Mechling's Scale-Oil" used in the experiments was 28° Baume 

 at 65° F., and of "Scalecide" 25° Baume at 65° F. The B. G. 

 Pratt Company reports, "We use as a petroleum an asphaltum 

 base oil from which the light inflammable and lieavy lubricating 

 oils have been removed and which has an oil grav^ity of about 

 26°-30° Baume." The ^lechling Brothers jManufacturing Company 

 reports. ' Mechling 's Scale-Oil is composed of three entirely different 

 oils, a vegetable oil, a eresote oil and a paraffine oil. tlie largest 

 part l)eing the latter," and their guaranteed analysis shows 85-88 

 per cent mineral oil. The specific gravities of these two oils are 



