20 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 119 



Calycopis beon (Cramer). — Field [not Cramer, a misidentification], 1940, Bull. 

 Univ. Kansas, Biol. Ser., vol. 39, no. 10, pp. 142-143; 1940, Bull. Brooklyn 

 Ent. Soc, vol. 35, no. 4, pp. 134-135; 1941, Journ. Kansas Ent. Soc, vol. 14, 

 no, 2, pp. 66, 68-69.— Clench, in Ehrlich, P.B., and Ehrlich, A. H., 1961, 

 How to know the butterflies, p. 199. 



Strymon beon (Cramer). — Klots [not Cramer, a misidentification], 1951, Field 

 guide to butterflies of North America east of the Great Plains, p. 134. — doa 

 Passos, 1964, Synonymic list of the Nearctic Rhopalocera, p. 56. 



Male (figs. 71-74). — Ground color of wings above dark brown, 

 sometimes dark metallic blue; differing from the summer form of 

 C. cecrops on the hindwing in having a considerable amount of blue 

 in lower half of wing below ceU, occasionally with some blue in the 

 cell and thus similar to the spring form of cecrops. On the under- 

 surfaces it differs from both forms of cecrops by having the postmedian 

 tricolored band of the hindwing very much narrower at its broadest 

 point, being less than a millimeter in width and becoming even more 

 narrow toward the costal margin; in the forewing the red element of 

 this band is no wider than the black and white elements; on this 

 surface of the hindwing the middle section of the W-shaped mark is 

 more sharply angled than in cecrops; the black spot on anal lobe is 

 smaller than in cecrops and the red above this spot is more distinct; 

 the lunule adjacent to the W-shaped mark is always red in isobeon not 

 dark gray as in cecrops, and the black pupillated submarginal spots in 

 interspaces M3 and Cui are usually orange red (only rarely gray) with 

 smaller black pupils. 



Length of forewing 10-14 mm. 



Male genitalia, not illustrated, hardly differing from cecrops, except 

 for a slightly shorter aedeagus. In isobeon the average length of the 

 aedeagus is 3.24 mm. with the extremes of 2.33 and 3.75 mm., while in 

 cecrops this average is 3.75 mm. with the extremes of 3.50 and 4 mm. 

 In isobeon the aedeagus becomes progressively shorter toward the 

 southern limit of its distribution so that in Texas the average length 

 is 3.37 mm., in Mexico 3.19 mm., in Costa Rica 3 mm. and in Panama 

 2.66 mm. Eighth tergite (fig. 20^) with posterior concavity usually 

 more narrow than in cecrops. 



Female (figs. 75-78). — Differing from the male in having more blue 

 on wings above, the blue extending through discal cell of hindwing 

 and on base of forewing. On the undersurfaces it differs from cecrops 

 females in the same way that the males differ from that species. 



Length of forewing 10-13 mm. 



Female genitalia, not illustrated, not different from either cecrops or 

 Susanna 



Type-locality. — "Cartago, Costa Rica." 



Additional type data. — ^OriginaUy described from both sexes, and 

 although the number of specimens was not stated, only two specimens 



