SECONDARY SYMMETRY OF ASYMMETRIC 
GENITALIA IN MALES OF 
ERYNNIS FUN ERA LIS AND E. PROPERTIUS 
(LEPIDOPTERA: HESPERIIDAE) 
By John M. Burns 
Museum of Comparative Zoology, Harvard University 
The form of the genitalia is extraordinarily useful for distinguish- 
ing species in many animal groups, and nowhere more so than in 
the Lepidoptera. Indeed, in various genera — including some of 
those in Evans’ (1953) “Erynnis Group” of American pyrgine 
hesperiids — the genitalia have become asymmetric so that the num- 
ber of potential, taxonomically valuable characters is about doubled. 
Asymmetry of this kind was first described a century ago (Scudder 
and Burgess 1870) in males of Erynnis , where it is very pronounced. 
Out of 12,000 specimens whose genitalia I have examined in the 
course of microevolutionary studies of Erynnis (Burns 1964 and 
unpublished), two individuals have genitalia so deviant yet so har- 
moniously formed as almost to suggest new species. Both are males 
of Erynnides, a subgenus in which the valvae (or claspers) are 
characterized as “always highly asymmetric” (Burns 1964: 24) ; 
however, both “show striking secondary symmetry of the genitalia, 
in which the left valva is not its distinctive self, but instead, a mirror 
image of the right valva” (Burns 1964: 9). These variants belong 
to two of the species — Erynnis funeralis and E. propertius — that 
were described as new by Scudder and Burgess (1870) solely on 
the basis of morphologic differences in the asymmetric genitalia of 
males. 
In figs. 1-4, the symmetric valvae of the “half-wrong” variants 
are directly compared with their standard asymmetric counterparts. 
The secondarily established symmetry is extremely good in E. fu- 
neralis (fig. 2) but rather less exact in E. propertius (fig. 4) in 
which, for example, the distal ends of the ventral processes do not 
agree in detail. Clearly, there is no reversion here to some ancestral 
symmetric condition: in both E. funeralis (cf. figs. 1 and 2) and 
E. propertius (cf. figs. 3 and 4), the right valva in the symmetric 
variant precisely retains its modern shape, and it is this shape that 
the left valva duplicates. 
Both variants appear to have stemmed from developmental quirks. 
Experimental analyses of insect morphogenesis (see e.g. Ursprung 
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