NO. 10 TROPISMS OF LEPIDOPTERA — McINDOO 53 



We now have good evidence that both adult Lepidoptera and their 

 larvae can hear, although probably not as we do. Four kinds of so- 

 called auditory organs have been described. They are tympanic organs, 

 chordotonal organs, Johnston organs, and auditory hairs. The first 

 three have been found in adult Lepidoptera, while the second and 

 fourth occur in caterpillars. Of these four the writer found only the 

 Johnston organs in the adult codling moth, but Graber in 1882 saw 

 chordotonal organs in the codling-moth larva. It has been shown 

 experimentally that tympanic organs and auditory hairs are affected 

 by sound waves, but we know nothing definite about the functions of 

 the chordotonal and Johnston organs. 



Other special sensory receptors of the codling moth include certain 

 innervated hairs serviceable as tactile organs and a well-developed 

 structure in the labial palpus. The latter might function as a balancing 

 organ. The general senses to temperature, humidity, etc., are not 

 supposedly connected with special sense organs, although these senses 

 seem to be well developed in Lepidoptera. In connection with the 

 olfactory organs the scent-producing organs were studied. The only 

 one found in the codling moth is a pair of invaginated sacs in the 

 abdomen of males ; thus it seems that the males attract the females 

 and not the reverse. 



In conclusion it has been shown that considerable information is 

 now available on the tropisms and sense organs of Lepidoptera, but 

 there is much yet to be learned, and the problem should be attacked 

 from all angles, using the best equipment obtainable. A recent review 

 by Kennedy (38) helps to clarify certain phases of insect behavior. 

 He remarks that while sensitivity is a function of the nervous system, 

 it is conditioned by other structural features, such as small size and 

 chitinous exoskeleton. Hase (29) has recently described his physio- 

 logical laboratory and equipment at Berlin-Dahlem, which should be 

 emulated by other scientists doing similar work. Much of his appa- 

 ratus is used for testing the tropisms of insects. 



LITERATURE CITED 



(i) Abbott, C. E. 



1927. The effect of monochromatic light on Formica dakotensis specu- 

 lar is (Emerv). Ann. Ent. Soc. Amer. 20:117-122, 2 figs. 



(2) 



1927. The reaction of Datana larvae to sounds. Psyche 34:129-133. 



(3) Bertholf, L. M. 



1927. The relative sensitivity of honeybees to light of different wave- 

 lengths. Abstract: Journ. Econ. Ent. 20:521. 



