96 SELECTED NOTES FROM 



the lead indicated by the preceding segment, and the analogy pre- 

 sented by the Blow-fly where the anus opens between the dorsal 

 valves or appendages of the eighth and ninth segments. 



The relations of the succeeding parts, including the male gene- 

 rative organ, are very obscure. I have indicated my opinion about 

 them in the lettering of the figures, but feel it is little more than 

 conjecture. A. Hammond. 



Halteres of Diptera.— If the theory be true that in the Diptera 

 one pair of wings is modified into Halteres for the special purpose 

 of hearing, that sense ought to be considerably more acute in the 

 Diptera than in other insects. Is such the case? J. H. Green. 



Haltere of Blow-Fly. — I know that a certain mounter circu- 

 lates the Halteres as " Buzzing Organs " ; whatever they may be, 

 they are certainly not that. 



The Halteres of the Diptera take the place of the second pair 

 of wings in four-winged insects, and they are, in fact, transformed 

 wings. They are connected to the upper posterior sides of the 

 thorax by a joint, and are raised and lowered by special muscles. 



Their use seems to be to enable the insect to direct its flight. 

 They act by displacing the centre of gravity. Experiment shows 

 that, deprived of them, the insect, on attempting to fly, falls at 

 once ; but if a small weight be attached to the abdomen so as to 

 bring the centre of gravity behind the axis of suspension, the 

 power of directing the flight is restored (Compius Rendus, 1879, 

 p. 89). 



At the base of the haltere are four sets of special organs : two 

 sets on the upper and two on the lower surface. Each set consists 

 of a series of curved ridges, under each of which is a row of 

 hemispherical or oval vesicles, numbering nearly a thousand in all. 

 Each ridge is divided from its neighbour by a row of curved hairs. 



The vesicles are described by Dr. Hicks as openings in the 

 chitinous integuments, closed by a thin, cuticular membrane, 

 whereby a longer or a shorter tube is formed. 



Dr. Low^ne denies the assertion that the vesicles are openings 

 in the integument, and says they are lenticular corpuscles of high 

 refractive power. He considers the corpuscles to be otoconia and 

 the organs to be those of hearing ; and as a parallel instance 

 mentions that the auditory organs of some orthoptera are deve- 

 loped on their anterior femora. 



Dr. Hicks considers them to be organs of smell, their position 

 (close to the posterior thoracic spiracles, like the position of the 

 olfactory organs in the nostrils of vertebrata) being particularly 

 suitable for detecting odoriferous particles in the streams of air 

 inspired into the body. Which of the doctors is right ? 



The sense of which they are the organs is one of great import- 



