68 MR. K. M. SMITH ON CERTAIN SENSE-OROAKS 



There remains the curiously complex cone on which the 

 third joint is set : two explanations are possible : one is that it 

 is a method of rigidly fixing the third joint so that it cannot 

 damage the nerve ])y bending or twisting motion ; the other is 

 that the concentration in the third joint of the antenna of 

 volatile liquids expands it, puts pressure on the cone and gives 

 the fly the impulse to go where the excess of absorbed light will 

 vapourise, so relieving the pressure and also renewing the 

 sensitiveness of the organ. I put this forward as a mere 

 suggestion, but I think that some explanation of this curious 

 structure will be found and that any one who is further investi- 

 gating the behaviour of flies will find it useful. 



There is obviously scope for much detailed observation and 

 for correlated examination of the sense-organs. Mr. Smith's 

 paper offers a fine basis for this work, and if obsei-vation of habits 

 can be coi'related with investigation of structure, we should get 

 much further in our understanding of the senses and sense- 

 reaction of flies. 



H. M. Lefroy. 

 Imj'>erial Gollege of Science. 



References. 



(1) A. Berlese.— GliInsetti,vol.i. 1909, pp. 610-633, 693-695. 



(2) W. M. Wheeler. —Ants, 1910, p. 59 sqq. 



(3) E. P. Felt. — Circumfili of the Cecitlomyiidfe. 23rd E,ep. 



State Entomologist, being N.Y. State Mus. Bull. 124, 

 Albany, 1908, pp. 305-7. 



(4) A. S. Packard.— Textbook of Entomology, 1898, pp. 264- 



281. 



(5) W. Wesche. — Some new sense-organs in Diptera. Journ. 



Quekett Club, (2) vol. ix. 1904, pp. 91-104, pis. 6. 7. 



(6) -IST. E. McIndoo. — The olfactory sense of Hymenoptera. 



Proc. Ac. Nat. Sci. Philadelphia, vol. Ixvi. 1914, pp. 294- 

 341, pis. 11, 12. 



(7) W. M. Barrows. — The reactions of the Pomace fly, Droso- 



phila mnpelophila Loew, to odorous substances. Journ. 

 Exp. Zool. vol. iv. 1907, pp. 515-537. 



(8) E. RoHLER.— Zur Kenntniss der antennalen Sinnesorgane 



der Dipteren. Zool. Anz., vol. xxx. 1906, pp. 211-219. 



(9) E. RoHLER. — Beitrage zur Kenntniss der Sinnesorgane der 



Insecten. Zool. Jahrb., Anat., vol. xxii. 1905, pp. 225- 

 285, pis. 15, 16. 

 (10) P. DeegelXER.— Sinnesorgane, being Chap. 3 of C. Schroder's 

 'Handbuch der Entomologie,' vol.i. pp. 140-233 (Lief. 1-2, 

 1912-13). 



