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V. An experiment on the development of the male appendages 

 in Lepidoptera. By T. A. Chapman, M.D. 



[Read February 7th, 1912.] 



Plates XXXVII, XXXVIII. 



In the Proc. Ent. Soc, 1910, p. Ix, aud more at length 

 in the Proc. South London Ent. Soc, 1910-1911, p. 50, 

 I described (with photographs) a remarkable and so far as 

 I yet know a unique specimen of the $ genitalia of Acronycta 

 tridens found by Mr. Burrows. I thought it desirable to 

 investigate the matter more fully, and instituted some 

 experiments the results of which I report. 



Assuming the ^ appendages to be internal in the larva 

 and that they come to the surface at the pupal moult, not 

 of course becoming external as in the imago, but present- 

 ing on the surface the well-known two tubercles of the 

 pupa, it seemed that some abnormal result would appear 

 if such emergence from the interior could be prevented. 

 In order to attain this result, I produced in certain larvae 

 of Z. dispar a small cicatrix at the critical position between 

 the ninth and tenth abdominal segments in the midventral 

 line. The result was what I anticipated, the production 

 of specimens almost identical with Mr. Burrows's example 

 of A. tridens. The clasps, penis-sheath (joenis-tasche) and 

 penis (aedoeagus and vesica) form a mass in the interior of 

 the abdomen. 



The several organs are more or less recognisable, though, 

 for want of the usual position in which to develop, more or 

 less pressed together and distorted. Tliese specimens show, 

 as did Mr. Burrows's, the parts that remain external, as being 

 the actual ninth and tenth abdominal segments apart from 

 the special developments of which the appendages consist. 



So far as I can ascertain from the literature bearing on 

 the development of the male appendages, the parts 

 imprisoned thus in the interior develop from a body 

 described nearly a hundred years ago by Hero Id, and 

 called by him a Korperchen (a small body, a corpuscule). 



This corpuscule, though apparently a single mass, consists 

 really of two parts, one of which is strictly internal and 

 arises at the extremity of the seminal ducts, the other is 

 external and is an invagination of the posterior margin of 

 the ninth abdominal segment, and some trace of the line 

 of invagination connects Herold's corpuscule with the surface 



TRANS. ENT. SOC. LOND. 1912. — PART II. (OCT.) E E 



