4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 82 



Wodsedalek (97) has demonstrated that the phototactic resix)nses 

 of certain dermestids vary at different life-history periods. The 

 larvae of Trogoderma tarsale immediately after hatching are photo- 

 negative. Negative phototaxis persists throughout the larval period, 

 and even for a short time after the adults mate. Soon after oviposit- 

 ing, the females become gradually indifferent to light and later be- 

 come photopositive. 



Breitenbecher (7) experimented with potato beetles, under dry 

 and moist conditions, to ascertain what their tropic responses would 

 be in a desert. When the beetles were confined in a moist medium, they 

 were found to be photopositive and geonegative ; but when desiccation 

 resulted in a dry medium, they were photonegative and geopositive. 



Runner (69, p. 25) tested tobacco beetles with color screens or ray 

 filters which transmitted practically monochromatic light rays. He 

 remarks that these beetles, in common with other insects, reacted 

 most strongly to colors of .shortest wave length. The movement to- 

 ward blue or blue-violet was most pronounced, and the movement 

 toward red least of all. These beetles, like other insects reacting 

 negatively toward intense sunlight, were only slightly sensitive to 

 light at the lower end of the spectrum, and rays of longer wave length, 

 limited to red and orange, seemed to act on them in much the same 

 manner as darkness. Beetles exposed to bright sunshine under color 

 screens of red and 1)lue were observed to collect under the red screen 

 almost as readily as they did when an opaque screen was used instead 

 of the red, although the apparent intensity of light under the two 

 screens was the same. 



Smith (75) remarks that the larvae of the Japanese beetle are thig- 

 mopositive to living roots, and if these are not available, they adhere 

 to stones, sticks, or the bottom and sides of the breeding cage. The 

 adult beetles apparently can see colors, particularly green. This is 

 taken advantage of by painting the bait traps green and by using green 

 lead arsenate (78). 



Moore and Cole (56) report that Japanese beetles collect in great 

 numbers at the tops of trees, bushes, and weeds. This is caused by two 

 tropic responses — positive phototaxis and negative geotaxis, which 

 determine the head-tail orientation of the body. In the field and labora- 

 tory certain degrees of heat and light are necessary to cause active 

 movements. These writers further say that since a geotactic response 

 is shown by the beetles only when they are illuminated, it therefore 

 follows that their movement in a lighted 'field is the result of three 

 factors — negative geotaxis, photokinesis, and positive phototaxis. 

 The first is constant, while the other two factors are functions of the 



