306 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 4 



This was repeated twice and even on the following day none suc- 

 ceeded in crossing the soil. 



Purple Scale. — At 9 a. m., September 17, with a temperature of 

 86°, 25 young purple scales were placed unharmed in the center of 

 an area of sand having a 5-inch radius. None of these reached the 

 edge during the same day nor the day following. A similar experi- 

 ment resulted negatively. A third similar to the others was started 

 at 9.45 and out of 25 liberated one reached the margin at 3.30 (5 3-4 

 hours). This is the only one that succeeded in crossing a 5-inch 

 strip of sand. The following records were made on a 3-inch radius 

 of sand : 



9-20-10 T. 93° 20 liberated at 1.30 p. m. No results. 



9-21-10 T. 82° 20 liberated at 9.45 a. m., 2 out at 12.30 p. m. 



9-22-10 T. 65° 10 liberated at 9.30 a. m., 2 out at 1 p. m. 



No more emerged by 5 p. m. or during next forenoon. 



The experiments recorded here represent but a few of the total 

 number made, but they will serve to show how they average. In the 

 case of the black scale it was shown that about 4 feet of ordinary 

 orchard soil is about the limit that will be traversed by the active 

 young. Under favorable conditions they might, therefore, through 

 their own powers of locomotion make their way from one citrus tree 

 to another or to a second or third tree away. But the number thus 

 traveling would be exceedingly small as compared with the total. 

 These records were made on soil with an ordinary mulch. Tests were 

 made on their powers of traveling over compact soil and they invar- 

 iably showed very much greater progress. A compacted irrigation 

 furrow enabled even the young red scale to travel two or three feet, 

 while in a loose mulch this scale makes practically no progress. The 

 young red scale in attempting to ascend a small particle of earth falls 

 back again and this is repeated time after time. The same is almost 

 as true for the young purple scale. Where there is a fine mulch, there- 

 fore, the chances of the young red or purple scale reaching an adjoining 

 tree is practically negligible. 



