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Journal of the Lepidopterists' Society
Summary
Males perch from 0715 to 1100 on shrubs or trees in small clearings and dart out at passing objects in search of females. Mating usually involves male wing flicking. Unreceptive females flutter their wings until the male departs. Adults are very sedentary, although some individuals move several hundred meters. Both sexes live an average of only 4 days, probably because of hot weather and extensive predation. Both sexes often feed, usually on yellow or white flowers. Females oviposit mainly on Ribes branches.
Acknowledgment
I thank Jerry A. Powell for improving the manuscript.
Literature Cited
Burns, J. M. 1968. Mating frequency in natural populations of skippers and
butterflies as determined by spermatophore counts. Proc. Nat. Acad. Sci.,
Washington, D.C. 61: 852-859. Cook, L. M., L. P. Brower & H. J. Croze. 1967. The accuracy of a population
estimation from multiple recapture data. J. Anim. Ecol. 36: 57-60. Ehrlich, P. R. & S. E. Davidson. 1960. Techniques for capture-recapture
studies of Lepidoptera populations. J. Lepid. Soc. 14: 227-230. Emmel, J. F., O. Shields & D. E. Breedlove. 1970. Larval foodplant records for
North American rhopalocera. Part 2. J. Res. Lepid. 9: 233-242. Gunder, J. D. 1930. Butterflies of Los Angeles County, California. Bull. So.
Calif. Acad. Sci. 29: 39-95. Jolly, G. M. 1966. Explicit estimates from capture-recapture data with both
death and immigration—stochastic model. Biometrika 52: 225-247. Scott, J. A. 1973. Convergence of population biology and adult behaviour in two
sympatric butterflies, Neominois Hdingsii (Papilionoidea, Nymphalidae) and
Amblyscirtes simius (Hesperioidea, Hesperiidae). J. Anim. Ecol. (in press). Wickler, W. 1968. Mimicry in Plants and Animals. McGraw-Hill, New York.
160 p.
REPORT OF THE CAPTURE OF AN ADDITIONAL HYBRID BETWEEN
LIMENITIS ARTHEMIS ASTYANAX AND L. ARCHIPPUS
(NYMPHALIDAE)
On 15 October 1972, a wild male interspecific hybrid between Limenitis arthemis astyanax (Fabricius) and L. archippus (Cramer) [form rubidus Strecker] was captured in Durham County nine miles south of Durham, North Carolina. This specimen was captured approximately one-half mile from the site at which a similar hybrid was found two years previously on 10 October 1970 (Piatt & Greenfield 1971, J. Lepid. Soc. 25: 278-284). The specimen presently is in the collection of A. P. Piatt at the University of Maryland Baltimore County.
The recent hybrid (Fig. 1) is in good condition, showing little evidence of being flight-worn. It was quite vigorous in flight and eluded capture several times before being netted. This specimen closely resembles the lab-reared dark morph depicted by Piatt & Greenfield (1971); it entirely lacks all remnants of the medial partial white banding (an archippus character). On the other hand, the previously caught wild hybrid from Durham was battered, and clearly showed traces of the white
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Fig. 1. Wild-caught male L. aiihemis astyanax X L. archippus (hybrid form rubidus Stkr.) collected south of Durham, North Carolina on 15 October 1972 by J. C. Greenfield, Jr. Above: dorsal surface; below: ventral surface.
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Journal of the Lepidopterists' Society
banding on the ventrum of the fore wings. Otherwise, the two specimens appear to be morphologically identical, both representing the dark morph of rubidus.
The purpose of this note, in addition to reporting the new hybrid specimen, is to consider why two species as morphologically dissimilar in color pattern as the red-spotted purple and the viceroy should engage in interspecific hybridization in nature, even to the limited extent indicated by the capture of these rare rubidus hybrids. The occurrence of two (which are presumably genetically unrelated) in the same locality two years apart is unlikely in view of the scarcity of this form in the wild. A simple explanation is not readily forthcoming.
Adults of the two parental species are, however, quite prevalent in this area; both astyanax and archippus have been encountered in the same vicinity on multiple occasions, especially in the late summer, often congregating in an old orchard where the ground is covered with rotting fruit. Thus, the usual ecological separation of the two parental species by habitat preference does not seem to be as strongly in evidence in this area as in others.
The fact that both hybrids were collected at almost the identical time of year suggests that there exists a greater tendency for natural hybridization in the late summer and early fall. This contention may be substantiated by examining the collection dates for the known wild Limenitis hybrids listed by Piatt & Greenfield (1971). Of ten specimens for which dates are reported, nine (including all specimens of form rubidus) were collected in the months of August and September.
The single exception to this generality represents the most northern record listed: a hybrid specimen presumed to represent a cross between the western subspecies, L. arthemis rubrofasciata Barnes & McDunnough, and L. archippus, collected at Beulah, Manitoba on 29 June 1904 by A. J. Dennis (Gunder 1934, Canad. Entomol. 66: 39-48). Although originally described under the hybrid name rubrofascechippus (Gunder), it clearly represents a local variant of hybrid form arthechippus (Scudder), and has been so listed by Piatt & Greenfield (1971). Both the northern locality and the early collection date suggest that it also resulted from a fall mating, since the larva would undoubtedly have had to overwinter in order to produce an adult by late June. Finally, the most recent record of a rather aberrant morph of arthechippus (Johnson & Malick 1972, Rep. Flora & Fauna Wise. 7: 1-6) also has an August collection date.
Both L. a. astyanax and L. archippus are at least partially triple brooded throughout the eastern U.S. Young (lst-3rd instar) larvae of both species may frequently be found in the wild in Connecticut and Maryland in mid-September (L. a. astyanax commonly feeding on Prunus serotina Ehrh., and L. archippus on Salix spp. and Populus spp.). Twenty young archippus larvae were once collected at Middlefield (Middlesex Co.), Connecticut between 14-21 October 1968, all actively feeding prior to entering winter diapause (Piatt, pers. obs.).
Developing larvae of both species are known to construct hibernacula (from the basal portions of tubular rolled leaves spun with silk) and to enter facultative diapause at third instar during the late summer and fall, in response to shortened daylength (Clark & Piatt 1969, J. Insect Physiol. 15: 1951-1957).
During the summer of 1966, three successive generations of L. arthemis-astyanax larvae were reared from a stock obtained from the intergrading population located at Shutesbury (Franklin Co.), Massachusetts (Piatt & Brower 1968, Evolution 22: 699-718). A total of 8 broods representing the three generations were bred and lab-reared under the ambient daylength for southern New England (Connecticut and Rhode Island) at room temperature. The incidence of diapause among the three successive generations of larvae increased dramatically from July through October (Table 1).
Hong & Piatt (in prep.) have determined that the critical photoperiod (that which induces 50% diapause among developing larvae) in Maryland and Vermont strains of L. archippus, lab-reared at room temperature, falls between 13.0 and
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Table 1. Incidence of facultative diapause among three successive generations of L. a. arthemis-astyanax butterflies from central Massachusetts—1966 data.
No. of No. of Larvae
Generation Broods Larvae Diapausing (%)
1, early summer
(July) 1 144 2.1
2, late summer
(August-early September) 4 170 22.4
3, Fall (October) 3 66 98.5
Note: All broods were lab-reared on Prunus serotina Ehrh. at room temperature under the ambient photoperiod for Connecticut and Rhode Island.
13.5 hrs of light per 24 hr day. Photoperiods of 12 and 12.5 hrs per day induced diapause in 66-89% of the developing larvae representing these two strains.
The ambient daylength at Durham, N. Carolina (approximate latitude = 36°N) decreases from 14:30 in mid-June to 13:25 in mid-August and down to 12:23 by mid-September (Duncombe 1966, The American Ephemeris and Nautical Almanac. U.S. Gov't. Print. Off., Washington, D.C. 512 p.). On the basis of these data, and the diapause information given above, it is reasonable to assume that a high proportion of the larvae of both L. a. astyanax and L. archippus developing in the wild near Durham during August and September will enter diapause at third instar. Consequently, those larvae undergoing direct development in the late summer and fall will be relatively few.
The matings which produced both of the North Carolina wild hybrids had to occur either in late August or (more likely) in September, a time of year when the adults of both species are at relatively low true population densities, despite their apparent local adult abundance noted above. The late capture dates of both hybrids makes the possibility of their successful backcrossing to parent-type females extremely remote (Piatt & Greenfield, 1971). However, seasonably low late summer or fall temperatures perhaps serve to make L. a. astyanax and L. archippus females more sluggish behaviorally, and hence less particular with regard to selecting their mates. In conclusion, a scarcity of adult butterflies of both species (i.e. mates of the same species) may well contribute to a situation favoring natural interspecific hybridization in Limenitis.
Joseph C. Greenfield, Jr., Box 3246, Duke University Medical Center, Durham, North Carolina 27710.
Austin P. Platt, Department of Biological Sciences, University of Maryland Baltimore County, 5401 Wilkens Avenue, Catonsville, Maryland 21228.
MOVEMENTS OF NYMPHALIS CALIFORNICA (NYMPHALIDAE) IN 1972
Recent descriptions of the widespread 1971 eruptions of the California tortoise shell, Nymphalis californica Boisduval, (Nymphalidae) (Powell 1972, Pan-Pac. Entomol. 48: 144; J. Lepid. Soc. 26: 226-228) have prompted this report of observations in central California the following year. Weekly observations were made from 4000 to 7200 feet along Interstate Highway 80 in the central Sierra Nevada in Nevada and Placer counties from 17 May-27 October and on 29 March; during intensive collecting in the Sacramento Valley (Yolo, Solano, Sacramento counties) at 10-100 feet from 10 February-31 December; and frequently in the Vaca Mts., Yolo Co., from 14 March-6 July and occasionally through 29 December.