Ministrymon azia (Hewitson) (Fig. 1) is widely cited in faunal lists and occurs from the southern United States to southern Brazil, Paraguay, and Argentina in virtually all lowland habitats, ranging from desert in coastal Peru and Chile to rainforest in the Amazon Basin (Godman and Salvin 1887-1901, Draudt 1919-1920, Kaye 1921, Talbot 1928, Holland 1931, Stallings and Turner 1946, Hayward 1958, Brown and Mielke 1967, Ebert 1970, Lamas 1977, Robbins et al. 1996, 2012a, Gareca et al. 2009, Duarte et al. 2010). Adults of Ministrymon azia appear to be highly dispersive, having been recorded migrating through Portachuelo Pass in northern Venezuela and being dispersed by dry season trade winds in Panama (Beebe 1951, Robbins and Small 1981). Caterpillars of Ministrymon azia eat the flowers of a wide variety of Fabaceae and are discussed in the biological control and agriculture literature (e.g., Cock 1985, Harley et al. 1995, Fernández and Rodríguez 1997, Vargas and Parra 2009). The ventral wing pattern of Ministrymon azia west of the Andes is slightly different from that in other parts of its range, but genitalic variation is negligible (Johnson and Miller 1991). The nomenclature and taxonomy of Ministrymon azia are stable (Robbins and Lamas 2002, ICZN 2006). This species lacks a common name in the agricultural literature (Bosik 1997) but has been called Gray Ministreak in recent works dealing with North American butterflies (Cassie et al. 1995, Wauer 2004, Allen et al. 2005, Cech and Tudor 2005).

The generic placement of Ministrymon azia is a bit of an historical puzzle. Clench (1961: 196) described Ministrymon based on the presence of “two small erect ventral teeth near the tip” of the penis, but placed azia in Tmolus Hübner, a genus that lacks these teeth (as noted by Clench 1961). Ministrymon azia has four small erect teeth (Figs 5–6, first illustrated by Johnson and Miller 1991). It is puzzling that Clench did not observe the teeth because they are reasonably conspicuous. Robbins (2004a) listed 22 species in Ministrymon primarily based upon the presence of teeth on the ventral side of the penis near the tip. These teeth are otherwise unreported in the Eumaeini.

We recently discovered that the traditional species concept of Ministrymon azia includes a cryptic species that occurs sympatrically and synchronically with Ministrymon azia from the United States (Texas) south into the Neotropics. The cryptic species was discovered in Texas and Mexico (Glassberg 2005, 2012) because its adults have olive green eyes instead of the dark brown/black eyes of Ministrymon azia (Fig. 1). So far as we are aware, this is the first time that an undescribed butterfly species has been recognized on the basis of eye color, a point that is amplified in the discussion. We subsequently found that the genitalia and ventral wing patterns of these species differ substantially and consistently. It is the purpose of this paper to give the undescribed species a scientific name, to present data that support the hypothesis that it is biologically distinct, and to update information on the biology of these species using the new taxonomy.

Standard methods were used to dissect genitalia and to prepare them for examination with an SEM (Robbins 1991). Genitalic terminology follows that in Clench (1961) and Klots (1970), as modified for the Eumaeini (Robbins 1991). Forewing length was measured with a digital vernier caliper. Wing vein names follow Comstock (1918), and terminology for male secondary sexual characters follows Robbins (1991) and Robbins et al. (2012b). Museum specimens of Ministrymon janevicroy studied are deposited (unless otherwise noted) in the USNM (see below for repository acronyms). Thirty images of Ministrymon janevicroy in nature from Texas, Mexico, and Venezuela were assembled (most taken without a flash). For this study, specimens and images of Ministrymon janevicroy were compared with a study series of 550+ specimens of Ministrymon azia from 20 countries deposited in the USNM and with 44 images of individuals of Ministrymon azia in nature.

We list genitalic dissections in Supplementary file 1 Ministrymon Genitalia Examined, images in nature in Supplementary file 2 Images of Live Butterflies, and data on forewing length and frequency of eye-color in Supplementary file 3 Ministrymon janevicroy Datasets.

Museum specimens cited in this study are deposited in the following collections – museum acronyms from Evenhuis (1993).

AMNH American Museum of Natural History, New York, USA

BMNH The Natural History Museum [formerly British Museum (Natural History) ], London, United Kingdom

DZUP Museu de Entomología Pe. Jesus Santiago Moure, Universidade Federal do Paraná, Curitiba, Paraná, Brazil

FSMC Florida Museum of Natural History (Allyn Museum/McGuire Center), University of Florida, Gainesville, Florida, USA

MC Personal collection of Alfred Moser, Sao Leopoldo, RS, Brazil

TAMU Texas A & M University, College Station, USA

UCRC Entomology Research Museum, University of California, Riverside, California, USA

USNM National Museum of Natural History, Smithsonian Institution, Washington, DC, USA

Generic Placement and Identification. Ministrymon janevicroy is placed in Ministrymon because it possesses small erect teeth on the ventral surface of the penis near the distal end (Fig. 6). This synapomorphy for Ministrymon was proposed by Clench (1961) and has not been reported in other eumaeine genera. Other characters accord with this placement (Robbins unpubl.). Forewing vein M₂ arises closer to M₁ than to M₃ in the male (Fig. 8) and the corpus bursae of the female genitalia is posteriorly constricted (Fig. 7). These traits are widespread (but not universal) in the Tmolus Section of Eumaeini, to which Ministrymon belongs (Robbins 2004a). A male dorsal scent patch is situated at the distal end of forewing discal cell and is partially covered by dark brown wing scales (Fig. 9). Within the Tmolus Section, this type of scent patch occurs in all Ministrymon, all Tmolus, and some Nicolaea K. Johnson.

The hypothesis that Ministrymon janevicroy is reproductively isolated from the sympatric Ministrymon azia is well-supported. The male and female genitalic differences between the two are distinct and distinguishing (Figs 6–7). The variegated “pebbly-textured” ground color appearance of the basal part of the ventral hindwing (Fig. 2) is also distinguishing. The eye color difference is distinct and distinguishing in live individuals (Fig. 1) and in the majority of museum specimens. Ministrymon janevicroy is unrecorded from tropical wet lowland forest (>200 cm annual precipitation, Holdridge 1967) while Ministrymon azia occurs in both wet and dry habitats. Ministrymon janevicroy occurs from Texas to Costa Rica and on Curaçao and Isla Margarita. In contrast, Ministrymon azia occurs commonly in wet and dry habitats from Texas and Florida to southern Brazil and Argentina. In sum, the two species differ morphologically and biologically in many respects, supporting a hypothesis of reproductive isolation between Ministrymon janevicroy and Ministrymon azia.

The substantive differences in the genitalic structures of Ministrymon azia and Ministrymon janevicroy (Figs 6–7) could be interpreted to mean that these two taxa are not closely related within Ministrymon. However, these species are sympatric in the same habitats, have very similar wing patterns, and the same androconial structures. If reproductive isolation between these species evolved by sexual selection acting on the genitalia (e.g., Eberhard 1985, Arnqvist 1998, Hosken and Stockley 2004), then the genitalic differences observed could be a consequence of this evolutionary process, and is not an indication of a lack of relationship.

In the diagnosis and previous paragraphs, we distinguished Ministrymon janevicroy from Ministrymon azia because both share a similar ventral wing pattern. If Ministrymon janevicroy were more closely related to another described Ministrymon species, its ventral wing pattern would distinguish it immediately from that species.

Eye Color. The “hairiness” of adult eyes has been widely used in lycaenid taxonomy for more than a century (cf. Eliot 1973 and included references), but adult eye-color has not been used traditionally (e.g., Godman and Salvin 1887-1901, Scudder 1889, Draudt 1919-1920, Eliot 1973). More recently, Glassberg (2001, 2005) used eye color in live individuals to differentiate the lycaenid Cyanophrys goodsoni (Clench) from other Cyanophrys species and to distinguish between the lycaenids Strymon bazochii (Godart) and Strymon cestri (Reakirt). Ministrymon janevicroy was originally discovered in Texas and Mexico (Glassberg 2005) because its adults have olive green eyes in nature instead of the dark brown/black eyes of Ministrymon azia. Eye color in Ministrymon janevicroy appears to darken after death, but most museum specimens of Ministrymon janevicroy have lighter eyes than those of Ministrymon azia.

To provide context for the eye color difference between Ministrymon azia and Ministrymon janevicroy, we surveyed other Ministrymon species by recording eye color in museum specimens and in images of live adults. Ministrymon zilda (Hewitson) has a deep black eye color (an apparent autapomorphy), both in museum specimens and in live individuals. Ministrymon cleon (Fabricius) (cf. Duarte and Robbins 2010 for a note on identification of this name) has the same dark brown/black eyes as Ministrymon azia in museum specimens and in one image of a live adult. Museum specimens of all other described Ministrymon species are variable with most having lighter-colored eyes than those of Ministrymon azia—similar in color to those of Ministrymon janevicroy—and with a minority of individuals in each species having the dark brown/black-colored eyes of Ministrymon azia. Of these, we have examined images of live adults for nine species, all of which have olive green eyes.

This survey of Ministrymon adult eye colors leads to three conclusions. First, although similarity in wing pattern suggests that Ministrymon azia is the phylogenetic sister of Ministrymon janevicroy, adult eye color suggests that Ministrymon azia might be the phylogenetic sister of Ministrymon cleon. Clearly, a phylogenetic analysis of the genus is needed. Second, adult eye color is a useful taxonomic character in the field, but its use in the museum is more limited. In this case, all museum specimens in the “Ministrymon azia” complex with yellow-brown to brown eyes are Ministrymon janevicroy, but the converse is untrue. Third, the biological significance of adult eye color is yet unknown. There is no evident correlation with gender, habitat, or other biological traits.

Variation. While there was no discernible geographic variation in the morphology of Ministrymon janevicroy, three morphological aspects vary in single populations. First, when Hewitson (1873) described Ministrymon azia, he noted that the discal spot (= scent patch) was “indistinctly marked” in one male and was more conspicuous in another male. The same variation occurs in Ministrymon janevicroy. It is caused by variation in the color of the dark brown scales covering the scent patch (Fig. 9), not by variation in the presence of androconia. Second, there may be four or five small erect teeth on the penis, and in one dissection, there was an indication of yet another tooth. Third, as previously noted, eye color varies in museum specimens depending upon postmortem darkening, but this variation is not reflected in live individuals, so far as we are aware.

Biogeography. A number of Central American eumaeine species occur in deciduous dry forest from the southern United States (Texas) or Mexico to Costa Rica (Guanacaste), but are unrecorded further south and east in Panama and northern Colombia. This species list includes Arawacus sito (Boisduval), Cyanophrys goodsoni (Clench), Cyanophrys miserabilis (Clench), Michaelus hecate (Godman & Salvin), Ministrymon clytie (W.H. Edwards), Rekoa zebina (Hewitson), Strymon alea (Godman & Salvin), Strymon bebrycia (Hewitson), and Ziegleria hoffmani (K. Johnson). Ministrymon janevicroy is now added to this list. Of these, only Strymon alea (Isla Margarita) and Ministrymon janevicroy are also recorded on islands just off the north coast of South America, but not from the dry continental forests of northern Venezuela and northern Colombia. It is possible that remnant populations of species that were once more widespread persist only on these islands, but alternately, the mainland Guajira peninsula of Colombia/Venezuela is yet poorly documented.

There is one female in the Ministrymon azia species group in the USNM from the Brazilian state of Minas Gerais that has the olive green eye color and variegated “pebbly-textured” wing pattern of Ministrymon janevicroy, but a different postmedian line on the ventral surface of the hindwing. Additionally, two males of the same species in MC are genitalically distinct from Ministrymon janevicroy (genitalic images sent to us by A. Moser). This species is a potential phylogenetic sister species of Ministrymon janevicroy. We are collaborating with Moser to find more specimens with the intention of describing it.

Nomenclature. Seven names have been applied to the species now called Ministrymon azia (Robbins 2004a), and it is the purpose of this section to explain why these names do not apply to Ministrymon janevicroy. The name Thecla guacanagari Wallengren, 1860 (Ecuador), which has a ventral wing pattern that appears to be transitional between that of Thecla azia and Thecla brocela, was suppressed by ICZN Opinion 2144 (ICZN 2006). We examined the lectotype of Thecla azia Hewitson, 1873 (Mexico) in the BMNH and received images of its male genitalia (courtesy R.I. Vane-Wright and B. Huertas). It is the basis for our identification of this name. We examined the holotype of Thecla nipona Hewitson, 1877 (Brazil). It has the smooth-textured gray appearance on the basal half of the ventral wing surface. Also, Ministrymon janevicroy does not occur in Brazil. We examined the holotype of Thecla brocela Dyar, 1913 (USNM). Its ventral wing pattern is typical of those populations of Ministrymon azia that occur west of the Andes from southern Ecuador to Chile. The genitalia, gray smooth-textured appearance on the basal half of the ventral wing surface, and uniform dark brown/black eyes are the same as those of Ministrymon azia from elsewhere. We examined an image of the holotype of Ministrymon quebradivaga K. Johnson & L.D. Miller, 1991 (Chile). As with Ministrymon brocela, its wing pattern is typical of those populations of Ministrymon azia that occur west of the Andes from southern Ecuador to Chile. The genitalia illustrated in the original description are those of Ministrymon azia, not of Ministrymon janevicroy. We know Ministrymon hernandezi Schwartz & K. Johnson, 1992 (Cuba) from the original publication. The male genitalia illustrations are stylized renderings, but the placement of the teeth on the ventral penis tip and the shape of the cornuti place this name in the synonymy with Ministrymon azia. Further, Ministrymon janevicroy does not occur in the Antilles. Finally, we accord nomenclatural priority to Angulopis hernandezi K. Johnson & Kroenlein, 1993 (a male holotype) over Electrostrymon grumus K. Johnson & Kroenlein, 1993 (a female holotype), new synonym, and remove the latter name from the synonymy of Ministrymon azia. Robbins (2004a) had erroneously listed grumus as a synonym of hernandezi Schwartz & K. Johnson rather than as a synonym of hernandezi K. Johnson & Kroenlein. The name Angulopis hernandezi is currently placed in genus Ziegleria K. Johnson (Robbins 2004a, Duarte and Robbins 2010).

Faunal documentation. The Eumaeini fauna of the United States is well-documented, and most species described in the past 75 years have arguably been cryptic species that had been overlooked because of wing pattern similarity with known species. Specific examples are Satyrium caryaevorus (McDunnough), Satyrium kingi (Klots & Clench), Callophrys hesseli (Rawson & Ziegler), and Strymon solitario Grishin & Durden. To this list, we add Ministrymon janevicroy. In sharp contrast, slightly more than 20% of the Central and South American eumaeine fauna is undescribed (Robbins 2004b), but the vast majority of these undescribed species are exceedingly rare in museum collections, unlike Ministrymon janevicroy. Assessing variation of these rare species remains an obstacle to documentation.

Biology and updated taxonomy. The purpose of this section is to assess previously published biological information about Ministrymon azia in the context of the updated taxonomy. As noted in the introduction to this paper, Ministrymon azia occurs from the United States (Texas and Florida) to Chile in virtually all lowland habitats, ranging from desert in coastal Peru and Chile to rainforest in the Amazon Basin. The information in this paper is consistent with this statement, and we note that there are specimens of Ministrymon azia in the USNM from Hidalgo, Cameron, and Edwards County in Texas. Ministrymon janevicroy is restricted to dry deciduous forest and scrub, and its range is a subset of that of Ministrymon azia. These species appear to be sympatric wherever Ministrymon janevicroy occurs.

Ministrymon azia was the most common lycaenid migrating through Portachuelo Pass in northern Venezuela (Beebe 1951), and it was one of the species being dispersed by dry season trade winds on the Pacific slope of Panama (Robbins and Small 1981). There are 34 vouchers of Ministrymon azia and none of Ministrymon janevicroy in the USNM that were caught migrating through Portachuelo Pass. There are 12 vouchers of Ministrymon azia and none of Ministrymon janevicroy in the USNM that were being dispersed by dry season trade winds at the Cerro Campana ridge in Panama. The records of migration and dispersal would appear to refer to Ministrymon azia, not to Ministrymon janevicroy.

Published larval food plant records (all Fabaceae, one exception) for Ministrymon azia from areas where Ministrymon janevicroy does not occur are the plant genera Acacia Willd. in the United States (Florida) and Chile, Mimosa L. in Cuba, and Trinidad, and Leucaena Benth. in the United States (Florida) (Boscoe 1982, Cock 1985, Fernández and Rodríguez 1997, Vargas and Parra 2009, Glassberg 2012, images of the immatures of Ministrymon azia on Leucaena available from Chin-Lee, http://bugguide.net/node/view/133700, accessed April 22, 2013). Miller et al. (1997) wrote that caterpillars of Ministrymon azia in Florida will eat Schinus terebinthifolius Raddi (Anacardiaceae), but this anomalous record needs confirmation.

Reared museum specimens that we have seen have all been Ministrymon azia. We examined individuals of Ministrymon azia in the USNM that were reared from Leucaena in Florida (2♂, 2♀) and from Mimosa in Guerrero and Veracruz, Mexico (1♂, 1♀) and in Trinidad (2♀). In DZUP, there are reared specimens from Mimosa in Pernambuco and Rio Grande do Sul, Brazil (2♂). Finally, we identified an adult female that was reared from Prosopis L. in Tarapacá, Chile, but deposition of this specimen is unknown.

Other caterpillar food plant records are currently ambiguous and may refer to Ministrymon azia or to Ministrymon janevicroy. Harley et al. (1995) reared “Ministrymon azia” in Mexico and Venezuela from Mimosa, but the deposition of the vouchers is not known. In TAMU, there are reared adults from Leucaena (3♂, 3♀) and from Mimosa (4♂, 3♀) in the United States (Texas). In UCR, there are two reared individuals from Leucaena in Sonora, Mexico. These reared individuals need to be re-examined to determine their specific identify.