BEHAVIOR OF SOME SOIL INSECTS. 165 



subjected to special treatment, which will be discussed under the 

 experiments. The majority of the experiments on the larvae 

 were performed with the species Evarthrus sodalis. The larvae 

 of this species are about an inch long, vigorous, active, easily 

 collected, and could be found in a variety of situations. They 

 were dug in all kinds of situations, from dry or wet, black soil in 

 corn fields to wet, sandy or humus soil close to creek beds. The 

 larvae of the genus Harpalus were mostly collected in wet, sandy 

 soil close to a creek bed; but they were also taken in drier and 

 heavier soil. The larvae of the genus Amara were dug from wet, 

 sandy soil close to a creek and from moist, black soil in the bottom 

 of a depression which contained considerable humus. Larvae of 

 the genus Pterostichus were dug from situations similar to those 

 of Evarthrus sodalis. The adults were collected at various places. 



III. EXPERIMENTAL RESULTS. 



About one hundred and twenty-five experiments were per- 

 formed at various times during the fall, winter, and spring of 

 1915-16. Only a few representative ones, however, will be 

 given and discussed, together with any peculiar variations which 

 may need to be noted. 



i. LarvcB. 



A. Controls. The controls, which were conducted in still air, 

 were principally of two types as far as results were concerned. 

 The larvae were either active, crawling from one end of the cage 

 to the other, but occasionally stopping at either end to try to 

 crawl out, or they soon became quiet and remained in any part 

 of it and appeared to rest or sleep. At temperatures of about 

 1 8 to 22 C. the larvae were usually active and crawled from end 

 to end of the experimental cage. At temperatures below 18 C. 

 they were often inactive and remained quiet unless conditions 

 were otherwise unfavorable. At temperatures of 23 C. and 

 above the larvae were sometimes inactive but not at ease. The 

 increased temperature seemed to have a depressing effect and the 

 larvae acted tired and uneasy. Since in the normal controls the 

 larvae were either quite symmetrical in their movements or were 

 quiet, it was not thought necessary to give the control for each 

 experiment. Graph i shows the control for an Evarthrus sodalis 



