THE OLFACTORY SENSE OF COLEOPTERA. 455 



factory in function. If they really act as olfactory organs, then 

 the mouth parts, thorax, legs and sexual organs must aid in 

 receiving odor stimuli. Hochreuther considers the antennae more 

 important as appendages for carrying organs for receiving 

 mechanical stimuli rather than those receiving chemical stimuli. 

 According to various authors the antennal organs of different 

 beetles vary only sHghtly. The antennal organs of Dytiscus 

 are also similar to those of the honey bee. In both of these 

 insects the tactile hairs are of the same type. The Forel flasks 

 and pit pegs of the honey bee are two types of pit pegs which 

 are perhaps rudimentary, because the tips of the hairs do not 

 come to the exterior of the chitin. The massive pit pegs, 

 hollow pit pegs, and the sense bristles of Dytisais are certainly 

 nothing more than three types of tactile hairs. The hollow 

 pit pegs compare closely with the pegs of the honey bee, except 

 the pegs have thinner chitin af the tips. This is probably on 

 account of more acute sense of touch in the honey bee. The 

 pore-plate organs of the honey bee and the cup-shaped organs 

 of Dytiscus are also quite similar. 



One or more of the antennal organs of every insect studied 

 have been called olfactory organs, and it is possible that most of 

 these organs may be found on other appendages, besides the 

 antennae, as already seen in Dytiscus. 



In conclusion it seems beyond a doubt that none of the antennal 

 organs of beetles shown in Text-fig. 3 serves as an olfactory organ, 

 and that the olfactory pores are well adapted anatomically for 

 receiving odor stimuli, because the peripheral ends of their sense 

 fibers come into direct contact with the external air. 



LITERATURE CITED. 



Hauser, Gustav. 



'80 Physiologische und histologische Untersuchungen uber das Geruchsorgan 



der Insekten. Zeitsch. f. wiss. Zool., Bd. 34. Heft. 3, pp. 367-403, with 2 pis. 

 Hicks, J. B. 



'57 On a New Organ in Insects. Jour, Linn. Soc. London, Zool., Vol. i, pp. 



136-140, with I pi. 

 '59 Further Remarks on the Organs Found on the Bases of the Halteres and 



Wings of Insects. Trans. Linn. Soc. London, Zool., Vol. 22, pp. 141-45. 



with 2 pis. 

 '60 On Certain Sensory Organs in Insects, Hitherto Undescribed. Ibidem, 



Vol. 23, pp. 139-153. with 2 pis. 



