492 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 9 



sheets in the next arc, a distance of 46 yards, was 17 scales, and on the 

 next arc, a distance of 70 yards, 9 scales. All of these 60 scales came 

 from an amount of branches that would be represented bj^ a three- or 

 four-year-old tree. On the three sheets on the windward side, but 15 

 yards distant, there were no scales. 



Summary 



Young black scale, Saissetia olecc, have been found to be carried by 

 the wind, as represented by their capture on tanglefoot sheets, at 

 different distances up to 450 feet. This distance does not necessarily 

 represent the extreme dispersal since provision for capture was not 

 made beyond 450 feet. 



The young of the red scale (Chrysomphalus aurajitii) were captured 

 on tanglefoot sheets at distances ranging from 30 to 150 feet. 



It is possible that many of the scales on these sheets were dead at 

 the time of capture, but that there were many alive is shown by the 

 next statement. 



Young black scale were distributed over an entire four-acre block 

 of trees, without question chiefly by the wind, in a single season. They 

 may be distributed by the wind over a much greater area than this. 



That the spread is chiefly in the direction of the prevailing wind is 

 shown from the figures given for the block of trees, as well as by the 

 captures on the tanglefoot paper. 



In the case of young black scale, dispersion by the wind occurs 

 largely during the period of young production from Api'il to Sep- 

 tember. With scales having three or four generations a year, the 

 young producing period is prolonged and consequently the liability 

 of the young to be carried by the wind is prolonged. 



The data presented on the dispersion of scale insects by the wind, 

 which data represent only a preliminary report, emphasize the prac- 

 tical importance of carrying on fumigation work solidly over as large 

 an area as possible. 



H. S. Smith: Were the scales experimented with young newly 

 hatched larvae or older forms? 



Chairman H. J. Quayle: They were newly hatched larvae. 



D. L. Crawford: Which is the most responsible for the spread of 

 scale insects, wind, insects or birds? 



Chairman H. J. Quayle: Wind by far; birds and insects are very 

 small factors. 



Dr. E. G. Titus: I have found that the wind will carry young 

 thrips at a height of 20 feet. 



E. L. Prizer: Are birds and insects more likely to carry mealy- 

 bugs than wind? 



