152 



THE CANADIAN ENTOMOLOGIST 



NOTES ON SOME TROPIC REACTIONS OF MACRO- 

 DACTYLUS SUBSPINOSUS FAB. 



BY HARRY B. WEISS, NEW BRUNSWICK, N. J. 



During the summer of 1914, while investigating a "rose chafer" 

 complaint in southern New Jersey, a long wait for a train, an 

 abundance of beetles and favourable surroundings tempted me to 

 test the action of this insect in the field under different conditions 

 of light and temperature. 



A comparatively cool, shady woods, where the temperature 

 was 75 degrees F., a tree in the open under the shade of which the 

 temperature was 84 degrees F. and a dead leafless tree in the bright 

 sunlight where the temperature was 89 degrees F., constituted all 

 the apparatus at my disposal. Forty-five beetles were collected 

 while feeding and copulating and three batches of fifteen each were 

 liberated one at a time at the base of a tree in each of the sur- 

 roundings described above. The following table gives the distances 

 (vertical) covered by each beetle. 



Shade, Temp. 75 F. 



Beetle 



6 



7. 



8. 



9. 

 10. 

 11. 

 12. 

 13. 

 14 

 15, 



Distance 

 covered 



ft 

 .6  

 .3 • 

 .1 • 



5 • 

 .1 ' 

 .0 • 



2 • 

 .1 • 

 .0 • 



1 • 

 ') • 



.0 • 

 .0 • 



2 ' 



Totals 22 ft. 38 in. 



Averages 20.1 " 



At a shade temperature of 75 degrees F., the average distance 

 covered was 20.1 inches. At a shade temperature of 84 degrees F., 

 the average distance was 6.2 inches, and in the sunlight, with the 

 temperature five degrees higher, the average distance was 5.8 

 inches. It thus appears that thermotropism and phototropism 

 either together or alone were responsible for the quicker escape 

 of the insects into the air and the lessened distances covered. 



May. 1915 



