SIBLING SPECIES IN THE EURYDICE GROUP OF 
LETHE (LEPIDOPTERA: SATYRIDAE) 
By Ring T. Carde, 1 Arthur M. Shapiro, 1 
and Harry K. Clench 2 
Introduction 
We have uncovered a pair of sibling species in the comparatively 
well-known butterfly fauna of eastern North America.: the common 
Grass Nymph or Eyed Brown, Lethe eurydice of recent authors, 
is actually two species, which are extensively sympatric. 
Curiously, the distinctness of these two has been known since at 
least 1936, when W. D. Field discovered and characterized them 
as subspecies. He assigned names to them which we now know 
to be inapplicable. This was corrected in 1947 by R. L. Chermock, 
who named the presumably more southern “subspecies” appalachia. 
Neither of these authors was aware that the “subspecies” are sym- 
patric. 
The present investigation was first suggested when one of us 
(Clench) found both forms flying in the same area near Leesburg, 
Mercer Co., Pennsylvania in 1966. The conspicuous habitat differ- 
ence between them implied that two species might be involved. In 
1968 another of us (Shapiro) found the same situation in western 
and central New York and (with Carde) investigated the immature 
stages and biology of the insects. The results of this study are partly 
reported elsewhere (Shapiro and Carde, 1970). 
Independently of us, C. F. dos Passos and his correspondents 
simultaneously made the same discovery. Several of the conclusions 
contained in the resulting paper (dos Passos, 1969) appear erroneous. 
Since the taxonomic situation is very complex, we here review the 
whole subject, nomenclatorially, morphologically, and distributionally. 
In brief, we recognize two species in this group, as follows: 
(la) Lethe eurydice eurydice (Johansson), widely distributed from 
Labrador to Great Slave Lake and south to Delaware and Illinois, 
occurring in open marshes and sedge meadows. 
(ib) Lethe eurydice fumosa (Leussler), scattered in small isolated 
colonies (many now extinct) in sedgy permanent marshes in the 
’Department of Entomology and Limnology, Cornell University, Ithaca, 
N.Y. 14850. 
2 Section of Insects and Spiders, Carnegie Museum, Pittsburgh, Pa. 15213 
* Manuscript received by the editor April 24, 1970. 
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