THE OLFACTORY SENSE OF COLEOPTERA. 433 



to the other three already mentioned, these mutilated beetles 

 drank, ate and buried in the earth normally, but they were less 

 active than unmutilated ones. It was common to see them biting 

 the dorsal sides of the abdomens. Before they died several of 

 their abdomens had shrunk considerably in size. When found 

 dead several of them had been entirely eaten except the chitinous 

 parts. Counting from the time the elytra and wings were pulled 

 off, they lived from 5 to 21 days with 10 days as an average. 



The Olfactory Sense of Harpalus caliginosus. 



Eight ground beetles {Harpalus caliginosus) were caught under 

 flat stones. They were tested with the odors from only the three 

 essential oils. In behavior, they were comparatively quiet. 

 When tested, many of them moved away quickly; a few vibrated 

 the antennae, and a few moved their legs. 



Their reaction times are as follows: Oil of peppermint, 2 to 10 

 seconds, average 4.4 seconds; oil of thyme, 2 to 8 seconds, aver- 

 age 4.1 seconds; oil of wintergreen, 2 to 8 seconds, average 4.1 

 seconds. The general average reaction time to all three odors is 

 4.2 seconds. The antennae of these beetles were pulled off and 

 the insects were then kept in a small box containing earth in the 

 table drawer. 



{a) Effects with Antennce, Fulled Off. 



Eight days after the antennae of the eight preceding Harpalus 

 caliginosus had been pulled off, the remaining six live ones were 

 again tested with the same odors in the usual way. Their 

 responses were similar to those given before they were mutilated, 

 but were not so pronounced. When tested with the oil of thyme, 

 one beetle rubbed a hind leg on an elytron for a half minute. 



Their reaction times are as follows: Oil of peppermint, 3 to 25 

 seconds, average 12.5 seconds; oil of thyme, 4 to 60 seconds, 

 average 14.3 seconds. One failed to respond to this odor. 

 Oil of wintergreen, 10 to 35 seconds, average 22.5 seconds. The 

 general average reaction time to all three odors is 16.4 seconds. 

 These mutilated beetles were quite inactive and sometimes 

 scarcely moved when touched with a pencil. They did not eat 

 as greedily as before being mutilated. They lived from 2 to 65 

 days with 18 days as an average. 



