June, '11] quayle: scale insect locomotion 305 



the edge of the plate. Distance traveled 4 inches. A similar experi- 

 ment with ordinary orchard soil gave similar results. 



Temperature 84°. A plot of orchard soil one foot square was enclosed 

 with paper and several hundred active young liberated. When the 

 experiment was begun the morning was foggy. In 55 minutes three 

 reached the paper, a distance of 6 inches. By this time the sun was 

 shining and the temperature had arisen to 96°. At a temperature of 

 102° all the scales died. 



Temperature 85°. Four hundred or five hundred young were 

 liberated in the center of an area of soil 2 feet square at 10.15 a. m. 

 By 12.30 p. m. about 20 reached the margin; by 1 p. m. nearly 50, and 

 at 5 p. m. about 100. Distance traveled 1 foot. Similar experiments 

 showed that with a 2-foot strip of soil to cross, the first insects reached 

 the margin in approximately 2 hours. Where the width of soil was 

 4 feet, out of several hundred liberated only a very few succeeded in 

 crossing it during the same day. 



Experiments relating to the effect of high temperatures on young 

 black scales showed that it is an important factor in the causes of 

 death. Several hundred young black scales were liberated on white 

 cardboard in the sun with a temperature of 94° to 100°; at the end of 

 two hours they were unharmed by the heat. A similar experiment 

 is recorded with a temperature of 106° to 110°. At 106 the scales were 

 lively, but as the temperatures increased they moved more slowly, 

 and at 110 almost all movement ceased, although a 2 hours' exposure 

 did not kill them. 



Several hundred just emerged black scales liberated on soil with a 

 temperature of 108° to 110° were active for about 1 hour, but at the 

 end of that period some were dead and at the end of 13^ hours 

 nearly all had been killed. A check lot in the shade were not affected. 

 A large number of young placed upon a board with a temperature 

 of 118°, all died in 5 minutes. Scales exposed in sun on soil where 

 temperature was 119° to 122° died within 15 minutes. Under similar 

 conditions with temperature of 130° death resulted in 5 minutes. A 

 check lot in the shade were not affected. 



Red Scale. — Fifteen active young picked from orange were liberated 

 in sand with a radius of 1 inch. Two had radii of 2}^ inches, and 2 

 more measured 3 inches in radius. None crossed the soil, even in 

 the narrowest strip of sand. One particular insect was watched 

 closely for }4 hour and in that time traveled but a small fraction of 

 an inch. Another experiment showed that 1 scale out of 20 liberated 

 crossed a 23/^-inch strip in 18 hours. This was repeated the following 

 day when none crossed over the soil. Twenty were liberated in the 

 center of a 2-inch radius of soil and none reached the edge in 3 hours. 



