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NOTE ON A PECULIAR SECONDARY SEXUAL CHARACTER 

 FOUND AMONG GE031ETRIBAE AT THE SENSORY 

 ORGAN SITUATED AT THE BASE OE THE ABDOMEN. 



By KARL JORDAN. 



IT was in ISii."), I think, wlieu I first jjave an ojiinion on tlie abdominal sensory 

 organ referred to in the beading of this note, bnt quite jirivatel}*. An 

 Australian bad returned to London witli a collection of insects. Among the 

 Lepidoptera there were some of those well-kuown Australian Af/aristiflae which 

 bear in the male a stridulating organ on the wings, the sound being produced by 

 pressing the tarsi against the ribbed scaleless areae of the wings when in motion. 

 I asked the collector if he had ever noticed the sound made by these insects. " Oh 

 yes," he said: " 5 on can hear it twenty yards off. It's quite a load tse-tse-tse-tse." 

 And, picking up a specimen, he added, " Here is the hole they do the whistling 

 with," pointing to the first abdominal segment, which has the appearance of being 

 pierced by a round channel from side to side. " Oh, no," I replied ; " you are showing 

 me ii. female, which does not whistle: these ladies don't. Look at the difference in 

 the wings of the two sexes. That transjiarent space there in the male is the 

 whistling organ. This hole is present in both sexes, as yon see." And, taking 

 ranch for granted, I continued, with a confidence worthy of a priest who is trying 

 to convince a layman of the truth of some dogma, " That hole is an ear." 



The existence of the basal abdominal sensory organ in various families of moths 

 is well known (Guenec, Sharp, Swinton, etc.). When studying the Ayaristidae in 

 ls95, and the Ihjpsiidae { = Aganai<lae) in 1895 and 1896, I was much struck by 

 the diverse development of the structure in these two families. To understand the 

 difference, I comj)ared these organs in other families, and found that the moths can 

 be grouped aci-nrdin.i; to the develoiimeut of this organ. For lack of time I have 

 not been able to complete the researches so far that they can be presented to the 

 scientific public. But I hope to find now and again an occasion to draw the 

 attention to some of the ]-eciiliarities of this organ with its kettle-drums and 

 accessory structures. I f)nly mention to-day that tlie Lepidoptera can be classified 

 into three groups : — 



(1) The families which are devoid of the organ : here belong all the Butter- 

 flies, the Notodontidae, Cerfitocum/iiilKe, Saf/'riuidae, Siphlngidae, Bomhijeidae, 

 t'ossidne, Aegeriidae, etc. 



(2) The families in which the cavity lies underneath tlie pleura of the first 

 abdominal segment, the pleural plate being usually ranch swollen, and the edge of 

 the month of the cavity being more or less vertical : here belong the H>/psidac 

 { = Aganaidae), Arctiidac, Sgntomidae, Soctiiidae, Agaristidae, etc. In the 

 Agaristidae there is an interspace between the tergite of the first abdominal 

 segment and the pleural i)lates ; the two cavities thus formed, one on each side of 

 the body, are separated in the mesial jilaue of the body by a vertical transparent 



