1917] ECONOMIC ZOOLOGY — ENTOMOLOGY. 661 



The results show that nicotin sulphate is nonvolatile, but that alkalies con- 

 tained in hard water and soap set free tlie nicotin contained in nicotin sul- 

 phate sprays. Thus, in order to obtain the maximum efficiency of tobacco ex- 

 tracts containing nicotin sulphates, they should be rendered alkaline before 

 using. This is thought to explain the different results obtained in the use of 

 tobacco extracts, and also why soap greatly inci'eases the efficiency of sprays 

 containing nicotin sulphate. The fact that nicotin sulphate is nonvolatile also 

 explains the cases of poisoning from eating lettuce sprayed with tobacco ex- 

 tracts containing this material. 



" Commercial tobacco extracts containing nicotin sulphate should not be used 

 in the greenhouse, at least not on plants which are later to be used for food. 

 Tobacco extracts or tobacco papers containing free nicotin may safely be used 

 in the greenhouse on plants such as lettuce without endangering the lives of the 

 consumers. Food plants such as lettuce sprayed with tobacco extracts contain- 

 ing free nicotin should not be cut for the market until the day after spraying. 

 If the temperature of the house is low, a longer period should be given the 

 nicotin to evaporate from the leaves." 



Grasshopper control, C. R. Jones {Colorado Sta. Bui. 23S {1911), pp. S-29, 

 figs. 17). — A summary of information on the general life history, habits, and 

 practical methods of control of grasshoppers, based upon work in Colorado 

 during the outbreaks of 1916. The subject is taken up under the headings of 

 life history ; food habits — the plants affected ; natui'al and artificial control ; 

 apparatus for capturing gi-asshoppers, including the hopperdozer, balloon 

 catcher, and the live hopper machine ; insecticides ; diseases ; etc. The bulletin 

 concludes with a discussion of the work during 1916. 



A further contribution to the study of Eriosoma pyricola, the woolly pear 

 aphis, A. C. Baker and W. M. Davidson {U. 8. Dept. Agr., Jour. Agr. Research, 

 19 {1917), No. 2, pp. 65-74, Pls. S, fig. 1). — In the present paper, which gives the 

 complete life of cycle of E. pyricola, the authors first discuss the history of the 

 different species of plant lice recorded on pear roots {Pyrus communis) at some 

 length. The species ProdphiUis pyri (Fitch) has been found to be a homonym 

 and the name P. fltchii is proposed for it. It is shown to be definitely estab- 

 lished that the European pear-root aphis {E. pyri Goethe), described in 1884, is 

 the alternate form of the elm species E. lanuginosa (Hartig) of 1841. 



In a paper previously noted (E. S. R., 35, p. 463) the authors described the 

 American woolly pear aphis, previously thought to be the woolly apple aphis, 

 under the name E. pyricola and called attention to its close resemblance in gen- 

 eral structure to European specimens of E. lanuginosa. Studies since con- 

 ducted have shown that the marked difference in the wax pores and minor dif- 

 ferences in the sensoria then considered as representing a very distinct species 

 are not the same in the spring forms living on elms as in the summer and fall 

 forms living on pear roots, those in the spring forms being very similar to those 

 of E. lanuginosa. The very great similarity between the spring forms of E. pyri- 

 cola and E. lanuginosa has led the authors to believe that the same variation 

 will be found between the spring and fall forms of E. lanuginosa, which if it 

 proves true — and it is regarded as all but proved — will result in E. pyricola 

 becoming a synonym of E. lanuginosa. 



Thus it would appear that " the destructive woolly pear aphis of this country 

 is a European insect imported into the Western States on pear stock. It has 

 spread rapidly in the West in the last 25 years and now occurs from Washington 

 to California, although as yet it Is most destructively abundant in California. 

 The isolated infestations in the Middle West and in the East are due to separate 

 Infested importations. While the alternate vdnter forma thrive best on Euro- 

 pean elms, the species is able to live successfully upon the common American 



