434 N. E. MCINDOO. 



COCCINELLID^. 



The Olfactory Sense of Epilachna borealis. 



Many lady beetles {Epilachna borealis) were caught on pumpkin 

 vines in the corn field. When brought to the laboratory, they 

 were put into a large glass jar near a window. The jar was ii 

 inches tall and 9 inches in diameter. It was covered with cheese- 

 cloth. Since this lady beetle feeds upon the leaves of pumpkin 

 and of allied plants, several pumpkin leaves were put into a wide- 

 mouthed bottle containing water. The bottle with contents 

 was then put into the jar. The beetles soon found the leaves 

 and from that time on, they appeared "at home" as much as 

 they do in corn fields on pumpkin leaves. They were regularly 

 provided with a fresh supply of food. Occasionally they were 

 seen copulating. 



On the following day after being caught, 18 of them were 

 removed from the jar and were put singly into the experimental 

 cases. When mechanically irritated they draw in the antennae 

 and legs, usually eject a small drop of yellowish liquid from each 

 femoro-tibial articulation, and feign death. They may lie 

 apparently lifeless for several moments and when tested with 

 odors they may or may not respond. Owing to this peculiar 

 behavior, they were unsatisfactory to experiment with and 

 their average reaction times are slower than might be expected. 

 They were extremely quiet and when tested they generally moved 

 away slowly. They often vibrated the antennae and mouth 

 parts, and sometimes the legs. 



Their reaction times to the odors from the three essential oils 

 are as follows: Oil of peppermint, 2 to 55 seconds, average 12.4 

 seconds; oil of thyme, 2 to 20 seconds, average 6.8 seconds; oil of 

 wintergreen, 3 to 60 seconds, average 22.2 seconds. Three failed 

 to respond to this odor. The general average reaction time to all 

 three odors is 13.8 seconds. Sixteen of these insects were muti- 

 lated for other experiments. The seventeenth lived only 3 days 

 and the eighteenth is still living at this writing (Jan. 15). 



(a) Effects with A ntennce Pulled Off. 

 The antennae of 25 Epilachna borealis, just caught, were pulled 

 off at their bases. A small drop of yellowish blood exuded from 



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