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278

Journal of the Lepidopterists' Society

INTER-SPECIFIC HYBRIDIZATION BETWEEN LIMENITIS ARTHEMIS ASTYANAX AND L. ARCHIPPUS (NYMPHALIDAE)

Austin P. Platt

University of Maryland Baltimore County, Catonsville, Maryland

and

Joseph C. Greenfield, Jr.

Duke University Medical Center, Durham, North Carolina

The Nearctic genus Limenitis (Nymphalidae) contains five common, geographically widespread forms, all of which are polytypic, and exhibit tendencies toward hybridization (Edwards, 1879; Scudder, 1889; Field, 1904; Gunder, 1934; Remington, 1958, 1968; Gage, 1970). Four of the forms are mainly allopatric in their distributions, occupying adjacent regions, and coming in contact only along certain margins of their ranges (Hovanitz, 1949). Included among these are two conspecific eastern forms: the banded purple (L. arthemis arthemis Drury) and the red-spotted purple (L. arthemis astyanax Fabricius), an unbanded mimic of the blue swallowtail (Battus philenor L.). In addition, there are two western disruptively banded species: Weidemeyer's admiral (L. weide-meyerii Edwards) and Lorquin's admiral (L. lorquini Boisduval).

These four forms are closely allied, and conform well to Mayr's (1963) definition of a "super-species." The two subspecific eastern butterflies exhibit "free-interbreeding" and complete intergradation within the northeastern United States and southern Ontario (Edwards, 1877; Field, 1910; Hovanitz, 1949; Platt and Brower, 1968; Remington, 1968; Platt, Frearson, and Graves, 1970), whereas, the two western species exhibit "suturing" and "intense" interbreeding in certain restricted localities, often associated with mountain passes (Brown, 1934; Perkins and Perkins, 1966; Perkins and Perkins, 1967; Remington, 1968).

The fifth form is the predominantly orange-colored Viceroy (L. archippus Cramer). It is broadly sympatric with all four of the others and represents a distinct species having: a) evolved a mimetic color-pattern closely resembling the unpalatable monarch (Danaus plexippus L.), b) possessing highly modified male claspers (Scudder, 1889; Nakahara, 1924; Chermock, 1950; Platt, Frearson, and Graves, 1970), and c) being, in part, at least, ecologically isolated from the others, preferring open marshy meadows to woods-meadow ecotones and woodland glades.

The purposes of this report are: first, to document the occurrence of a recently collected wild hybrid between the two mimetic species, L. a. astyanax and L. archippus; second, to review previously known records of such inter-specific wild hybrids in order to verify the scarcity and wide geographic distribution of such specimens; and, third, to present a pre-

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1cm

Fig. 1. Wild-caught hybrid male (form rubidus Strecker) from Durham, N. C. with parental species; top row dorsal, bottom row ventral. Left, Limenitis archippus; middle, hybrid form rubidus; right, Limenitis arthemis astyanax.

liminary report of recent laboratory crosses which confirm the hybrid nature of these intermediate "suspected" wild hybrids.

The new hybrid specimen (Figure 1) is a male, collected on Highway 751, eight miles south of Durham, Durham County, North Carolina, on October 10, 1970 by J. C. Greenfield, Jr.1 It can be referred to hybrid form rubidus Strecker, in that its basic ground color is orange like that of archippus but the dorsal surfaces of the forewings are darkly pigmented, whereas, the hind wings possess large red-orange marginal spots. Ven-trally, both the proximal and marginal red-orange spotting and remnants of the double row of marginal iridescent lunules characteristic of astyanax are present. Both parental species fly commonly in the fields and woods surrounding the vicinity where the specimen was secured.

Other known records of wild hybrids between butterflies of the L. a. arthemis-astyanax complex and L. archippus are given in Table 1. By reviewing the literature, and corresponding with museum curators and Society members, a total of eight records of wild arihemis X archippus hybrids (form arthechippus Scudder), and 12 previous reports of wild-caught rubidus have been found. The wild specimens are widely distributed, but exceedingly rare, those reported in Table 1 having been collected from 1872-1970. Insofar as is known, all wild specimens collected to date have been males.

1 This specimen has been donated to the collection of the American Museum of Natural History in New York.

Table 1. Records of 20 previous wild-caught Limenitis arthemis astyanax X L. archippus hybri tion was not available.

State or province

LOCALITY

County

Township

Date

No. and                Coll

Sex1                      Col

Quebec

Maine

New Hampshire

Manitoba New York

New York Total

L. a. arthemis X L. archippus (arthechippus Scudder)2 -------                    Chateauguay Basin

Penobscot Cheshire

Tompkins Albany

Vic. Montreal Passadumkeag

Alstead

Beulah Dryden

East Berne

1879 "many yrs. ago" (2nd brood) 1895,1896, 1902 (seen) VI.29.1904 VIII.6.1967

VIII.8.1938

IS

1

3S S

is-is

IS

J. G.

L. P.

W. L. A. J. D A. M.

E. Sta

1  Insofar as is known, all specimens collected to date have been males.

2  Eight male arthechippus were reared by Field (1914) from an L. archippus Q X L. a. arthemis c? cross. Other cently by Piatt.

3 A 9 L. a. astyanax X d L. archippus were collected in copula VIII. 26. 1957 in a barnyard by Mrs. H. E. Hann The two specimens are in the AMNH (Dr. F. H. Rindge pers. comm.).

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K^H

Fig. 2. Lab-bred Fi L. arthemis astyanax x L. archippus hybrids; top row dorsal, bottom row ventral. Left, light (archippus-\ike) form; right, dark (astyanax-Mke) form. Specimens bred from Maryland stocks in January, 1970.

Proof of the hybrid nature of rubidus requires experimental crosses between the two parental species. As noted in Table 1, there is at least one record of astyanax and archippus having been collected in copula in the natural environment. Such hybrid crosses recently have been made by Piatt (Figure 2) by hand-pairing the insects (Piatt, 1969), and earlier ones are known to have been done at Yale University (C. L. Remington and R. W. Pease Jr. personal communication). To date, seven fertile crosses have been obtained by Piatt. Since these data will be reported in greater detail later, only a brief report of the findings will be included here.

Five crosses between astyanax females and archippus males have produced a total of 52 Fi male progeny. Two crosses between archippus females and astyanax males have yielded 78 Fi males, for a combined total of 130 Fi males. As shown in Figure 2, the inter-specific hybrids occur in both light (more archippus-\ike) and dark (more astyanax-like) morphs,

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Journal of the Lepidopterists' Society

the wild-caught specimen described above being of the darker variety (Figure 1). In contrast to arthechippus hybrids, all rubidus entirely lack the partial white band markings on their dorsal surfaces. However, some, but not all, have traces of the white band persisting in the costal regions of the fore wing, as does the recent wild-caught specimen. Such white markings are more fully expressed in archippus, but similar markings also are found in certain individuals of astyanax (Clark and Clark, 1951; Piatt and Brower, 1968).

The complete documentation of rubidus as an interspecific hybrid is shown by the fact that all bred Fi specimens obtained to date are males. Complete heterogametic (female) inviability is encountered when the two full species are hybridized, in accordance with Haldane's Rule (Steb-bins, 1958; Bowden, 1966).

However, recently the rubidus hybrids have been backcrossed successfully to both astyanax and arthemis females, and to archippus females, as well, yielding four viable broods having a total of 34 male and 12 female progeny (46 in all). Recovery of some of the females is noteworthy, although the sex ratios are still biased in favor of males (X2i = 10.52, P < 0.1). Only three males have been obtained so far in two backcrosses to archippus females, and breeding experiments are continuing.

Nevertheless, these preliminary broods demonstrate that the Fi male hybrids are fertile in backcrosses to the parent females. Genetic and phenotypic segregation also is apparent in these crosses, all combinations of which have yielded "parent-like" and "hybrid-like" individuals.

Environmental selection probably is operating against the rare naturally occurring hybrids. Since the two parental species are considered to be Batesian mimics of two totally different unpalatable models, such intermediate morphs become exceedingly poor mimics of cither one. The total female inviability encountered in Fi crosses means that the wild males must have to breed with parental females, if at all. Piatt, Frearson, and Graves (1970) have shown that arthechippus males possess valvae intermediate in shape between those of the two parent species; the same also undoubtedly is true of rubidus males. Consequently, sexual selection and mate choice, in which coloration and courtship behavior likewise are important, would not seem to be favoring the male hybrids.

In conclusion, the rare wild hybrid form rubidus Strecker represents a true inter-specific Ft hybrid arising from "stray" matings between two closely related, but distinct mimetic species, L. a. astyanax and L. archippus. As such, it illustrates well the breakdown of Batesian mimicry in the natural environment, and the selective elimination of an unfit phenotype.

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Acknowledgments

We are indebted to Dr. A. B. Klots and Dr. F. H. Rindge of the American Museum of Natural History for confirmation of the identity of the wild hybrid specimen, and for providing certain information given in Table 1. The assistance of Society members who have corresponded with Dr. Platt about hybridization in Limenitis also is gratefully acknowledged.

Literature Cited

Bowden, S. R. 1966. "Sex-ratio" in Pieris hybrids. J. Lepid. Soc. 20: 189-196.

Brown, C. 1934. Notes on Basilarchia lorquini Bdv., form fridayi Gun. (Lepid.: Nymphalidae). Entomol. News 45: 205-206.

Chehmock, R. L. 1950. A generic revision of the Limenitini of the world. Amer. Midi. Nat. 43: 513-569.

Clark, A. H., and L, H. Clark. 1951. The butterflies of Virginia. Smiths. Misc. Coll. 116: 1-239.

Edwards, W. H. 1877. Notes on Limenitis proserpina and arthemis. Canad. Ent. 9: 114.

Edwards, W. H. 1879. Butterflies of North America. Vol. 1: 111-147. (Privately printed).

Edwards, W. H. 1882. Description of new species of butterflies found in the United States. Papilio 2: 45-49,

Field, W. L. W. 1904. Problems in the genus Basilarchia. Psyche 11: 1-6.

Field, W. L. W. 1910. The offspring of a captured female Basilarchia. Psyche 21: 115-117.

Field, W. L. W. 1914. Hybrid butterflies of the genus Basilarchia. Psyche 21: 115-117.

Gage, E. V. 1970. A record of a naturally occurring Liminetis hybrid. J. Lepid. Soc. 24: 270-271.

Grey, L. P. 1968. (No title) In North American Annual Summary. News Lepid. Soc. No. 3, p. 19.

Gunder, J. D. 1934. A check list revision of the Genus Basilarchia Scud. (Lepid.: Rhopalocera). Canad. Ent. 66: 39-48.

Hovanitz, W. 1949. Increased variability in populations following natural hybridization. In Jepsen, G. L., E. Mayr, and G. G. Simpson (Eds.). Genetics, paleontology, and evolution. Princeton Univ. Press, pp. 339-355.

Klots, A. B. 1951. A field guide to the butterflies. Houghton Mifflin Co., Boston, pp. 115-116.

Mayr, E. 1963. Animal species and evolution. Belknap Press of Harvard Univ. Press, Cambridge, Mass.

Monroe, B. L. 1953. A hybrid Limenitis. Lepid. News 7: 53.

Nakahara, W. 1924. A revision of the genus Basilarchia (Rhopalocera: Nymphalidae). Bull. Brooklyn Ent. Soc. 19: 166-180.

Newcomb, H. H. 1907. Description of a new variety of Limenitis Ursula. Psyche 14: 89-91.

Perkins, E. M. and S. F. Perkins. 1966. A review of the Limenitis lorquini complex (Nymphalidae). J. Lepid. Soc. 20: 172^176.

Perkins, S. F. and E. M. Perkins, Jr. 1967. Revision of the Limenitis weide-meyerii complex, with description of a new subspecies (Nymphalidae). J. Lepid. Soc. 21: 213-234.

Platt, A. P. 1969. A simple technique for hand-pairing Limenitis butterflies (Nymphalidae). J. Lepid. Soc. 23: 109-112.

Platt, A. P. and L. P. Brower. 1968. Mimetic versus disruptive coloration in

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intergrading populations of Limenitis arthemis and astyanax butterflies. Evolution

22: 699-718. Platt, A. P., S. D. Frearson, and P. N. Graves. 1970. Statistical comparisons of

valval structure within and between populations of North American Limenitis

(Nymphalidae). Canad. Ent. 102: 513-533. Remington, C. L. 1958, Genetics of populations of Lepidoptera. Proc. Tenth Int.

Congr. Ent. 2: 787-805. Remington, C. L. 1968. Suture-zones of hybrid interaction between recently joined

biotas. Evol. Biol. 2: 321-428. Scudder, S. H. 1889. The butterflies of the eastern United States and Canada,

with special reference to< New England. Vol. 1. Published by the author, Cambridge, Mass., pp. 250-305. Shapiro, A. M. and J. D. Biggs. 1970. A hybrid Limenitis from New York. J.

Res. Lepid. 7: 149-152. Sterbins, G. L. 1958. The inviability, weakness and sterility of interspecific hy-

birds. Adv. Genet. 9: 147-215.

IDENTITY OF PHANETA REFUSANA (WALKER) WITH DESCRIPTION OF A NEW SPECIES (TORTRICIDAE)

William E. Miller

North Central Forest Experiment Station, USDA Forest Service, St. Paul, Minnesota

The name Phaneta refusana (Walker) is currently used for moths matching Heinrich's (1923) idea of Walker's species. Although Heinrich's interpretation is the most explicit available, Ileinrich never saw the Walker type. He perpetuated Kearfott's (1905a) identification which was based mainly on Walsingham's (1879) description and lithograph figure. Photographs of the holotype taken by N. S. Obraztsov at the British Museum (Natural History), and made available by the American Museum of Natural History, show that true refusana is actually different from the refusana of Heinrich. I confirmed this finding by examining the type itself at the British Museum. The misidentified moths have no valid name and I here propose a new one for them.

The letter n in this paper signifies the number of specimens observed for a particular statement. Values of n differ from the total number studied because all specimens were not satisfactory for all purposes. Forewing lengths (one wing) are given to the nearest 0.5 mm including fringe and excluding patagium. The generic name Phaneta is used as suggested by Obraztsov (1952).

Phaneta refusana (Walker), new combination

Grapholita refusana Walker, 1863. Semasia refusana; Walsingham, 1879.