THE EEPORT OF THE No. 36 



as it is an expression of the combined effects of air, temperature, pressure, 

 liumidity, wind velocity. 



This whole subject requires much additional study. 



The inter-relations of plants and insects become more involved when it is 

 known that certain varieties and species of economic plants are more liable to 

 attack by insects than other varieties and species. Treherne in a recent article 

 in the AgriculUiral Gazette of Canada brings forward some instances of this 

 kind. Spring wheat in certain localities in British Columbia is severely troubled 

 with the wheat midge, while fall wheat is seldom attacked. But he notes that 

 the early and late sowings of the spring wheat are not so seriously injured as 

 the mid-season sowing. Again, the grape-blossom midge injures the early varieties 

 of grapes, such as Morris Early, Warden, Champion and Massasoit, more than 

 the Concord. In the serious invasion of the Hessian Fly in Ontario in 1900-01 

 the writer observed that certain varieties of wheat wg-e injured more than others. 

 The Imperial, Egyptian and Michigan Ambers, Walker's Reliable and General 

 Grant, were but slightly infested, while Dawson's Golden Chaff, Turkey Red, 

 Treadwell and Red Chaff were badly affected. At the same time it was observed 

 that the Dawson's Golden Chaff was not seriously attacked in New York State. 



Treherne also notes that the Northern Spy apple is practically immune from 

 the woolly aphis, the Leconte and Kieffer pears from the San Jose scale, black 

 currants and lettuce from Peridromia saucia cut-worm-, and the red Dutch cab- 

 bages from the cabbage root maggot. In addition, he says : " The forest tent 

 caterpillar {M. disstria) attacks sugar maple in preference to the soft maple, 

 the latter being comparatively free from attack. He also records the fact that 

 the spiny elm caterpillar (E uvanes§a antiopa.) rather seriously injures American 

 elms, while Scotch and English elms are not preferred. Similarly, the maple 

 scale (Pulvinaria immnierahilis) rarely injures the sugar and Norway maples, 

 but attacks especially the soft maples. Dr. Felt has further rated various shade 

 trees in New York in their order of susceptibility or immunity from attack by 

 insects. The European elm sawfly (KaUosijsphvnga ulmi) attacks the English 

 and Scotch elms, including the Camperdown variety, in preference to the American 

 elms (Slingerland, Cornell). The elm leaf beetle (Galeracella luieola) is re- 

 ported as most seriously infesting the European elm and when other species of 

 elm were found growing nearby preference seemed to be shown for it (Burgess, 

 Illinois). The European elm scale (Gossyparia spuria) attacks the American 

 elms more seriously than the imported English elms. (Doten, Nevada.) The 

 fruit-tree bark beetle {Euzophem semifunemlis) clearly prefers the European or 

 imported varieties of plum, but does occur in the native kinds ; Pnimis simoni has, 

 however, thus far been worst affected by it. (Sanderson, Delaware). The white 

 peach scale (Diaspis pentagona) a very polyphagous feeder, does not attack the 

 Le Conte and Kieffer pears. (Gossard, Florida). The apple maggot (EhagoletU 

 pomoneUa) is noted particularly in the sweet and sub-acid summer varieties, 

 while fall and winter sorts, including acid varieties are less infested. (Quaintance, 

 U. S. Bureau.) The brown mite {Bryohia pratensis) is seldom observed on 

 quince and apricot, although it attacks a great variety of trees including almonds 

 and peaches. (Weldon, Colorado). The use of resistant vines against the grape 

 phylloxera represents a good example of the value of selection. The wild vines 

 of the Mississippi Valley states which have evolved in company with the Phylloxera 

 possess the more resistant forms. The European vine {Y. vmifera) is the most 

 susceptible of all in California. (Quayle, California.)" 



