186 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 3 



west, they have been very abundant for the past three years. Many 

 fine old elms have already succumbed to its attacks. 



Apatcla populi Riley was unusually abundant in all parts of the 

 city, in some cases poplars being defoliated by them. 



The red spider {Tetranychus bimaculaUts Harv.) was not so abun- 

 dant as last year, but nevertheless it was present in destructive num- 

 bers, especially on elm. Not only do the infested leaves become yel- 

 low and sickly looking, but they also fall prematurely. 



The wooly aphis of the hawtliorne {Schizoneura cratcegi Oestl.) was 

 present, as usual, in very destructive numbers. It is found almost 

 wholly on Cratcegus crus-galli, and is abundant in all the parks. 



The scale insects are of much importance in Chicago, the two most 

 prolific and destructive being the scurfy {CJiionasjns americana 

 John.) and the oyster-shell {Lepidosaphes ulmi L.). Although the 

 San Jose scale is present in Chicago, it multiplies very slowly, and 

 does not readily spread to nearby trees and shrubs. Inasmuch as the 

 scale is prolific and destructive twenty miles outside of the city, it ap- 

 pears probable that the reasons for its slow growth and spread within 

 the city may be due to one or all of the following : Few birds are to be 

 found in the city, and this lessens its chances of dispersal. The soot 

 and smoke, which is ever present, in combination with moisture, forms 

 acids, and this doubtless kills many individuals or weakens them so 

 that they are unable to survive the winter or it may retard their 

 growth. Further, the shrubs and trees in the city are poorly nour- 

 ished, and it is knovm that scale insects are less prolific on such 

 plants. 



Mr. Surface: The English sparrow is the chief transgressor in 

 carrying the San Jose scale in our state, and if it was abundant 

 in Chicago, I would suggest that it might be the chief cause of the 

 trouble. 



Mr. Braucher: I am inclined to believe that the slow spread of 

 the scale insects in Chicago is partly due to climatic conditions and to 

 the effect of the lake. In making observations on the time of hatch- 

 ing of the eggs of scale insects including the oyster-shell scale, I found 

 there w^as several days' difference in the time of hatching of the eggs 

 of the same species whether they were on trees close to the lake shore 

 or whether fifty to one hundred yards back in the park. Where there 

 is such a difference in so short a distance the lake must have a marked 

 effect in checking reproduction and development and consequently 

 the spread of the insect. 



Mr. Davis : The San Jose scale is a very injurious pest near 



