( G79 ) 



XIX. On asymmetry in the, Males of Hemarine and otheo' 

 ' Sphinges. By Thomas Algernon Chapman, M.D., 



F.Z.S. 



[Read May 7th, 1902.] 



Plates XXIV. and XXV. 



A want of bilateral symmetry in insects has been re- 

 corded of a great many different species and groups, in 

 many different orders. In the Lepidoptera, however, the 

 recorded instances are few, practically the only well-known 

 instance is in the genus Thanaos of Hesperid butterflies ; 

 I am indebted to Dr. Sharp for references to instances 

 occurring also in Butcdidse, Pterophoridm, and Psychidx, 

 recorded in a paper by Poljanec in Arb. Inst., Wien, xiii, 

 1901, pp. 155 — 19G, and he informs me that minor in- 

 stances affect certain Noetuidie. 



In the Sphinges it affects the whole family, probably 

 affects every species, though there are certainly a good 

 many in which, if present, it is reduced to so evanescent a 

 degree that I have not detected it. 



When asymmetry occurs in insects, it affects the sexual 

 appendages in a great majority of recorded instances, this is 

 so in all the cases of Lepidoptera I have just referred to, 

 and is also the case in the Sphinges. 



Gosse in his paper in the Linnsean Trans., mentions that 

 the ^dceagus of Papilio viennon is curved towards the 

 right side, and he implies vaguely a similar condition in 

 one or two other species. 



Except in the Hemarids, the asymmetry in Sphinges 

 affects only the a^devagus in any species I have examined, 

 and does so in many curious forms. In the Hemarines 

 (clearwings) it has gone further and affects the harpes, the 

 valves, and even the tegumen. 



My object in this paper is merely to call attention to the 

 facts from a morphological point of view, without attempt- 

 ing any systematic applications, beyond stating my belief 

 that a classification and revision of the Sphinges on the 

 characters of the male genitalia alone would give us 

 better results than any we now have, and that these azygos 



TRANS. ENT. SOC. LOND. 1902. — PART IV. (DEC.) 45 



