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Volume 28, Number 1
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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.
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Journal of the Lepidopterists' Society
Scattered worn, hibernated N. californica were seen in the valley during the weeks of 6 and 13 March and in the Vacas on 14 March. No more were seen until the week of 8 May when large numbers of seemingly fresh butterflies appeared throughout the Vacas. While this flight was in progress, occasional, fresh single tortoise shells could be seen in the valley, mainly along its west edge near Vacaville and Winters. On 26 May at 1700 hours a migration from west to east across the valley was observed from an elevated location just east of Davis, Yolo Co. Butterflies crossed a freeway overpass at the rate of one every 3 minutes, all headed due east. Most were flying from 30-60 feet above the vally floor, but a few were much lower. They continued moving through Davis from west to east most of the afternoon, at least until sunset. The movement was in progress again at 0900 the next day at comparable density. By evening it had dwindled somewhat, but stragglers continued to pass through Davis, moving from west to east, for about five days and a few individuals were seen at the east end of Yolo County, near the Sacramento River, as late as 27 June. On
2 June only one tortoise shell was seen in the Vacas where there had been hundreds before the migration, and on 12 June none were seen at all. Thereafter no tortoise shells were observed in the Vacas in 1972 (although hibernators were again numerous in February and March of 1973). After 27 June none were seen in the valley until mid-September.
On 29 March numbers of hibernated tortoise shells were flying in the Sierran foothills and up to 3000 feet. On 17 May at Baxter, el. ca. 4000 ft., hundreds of fresh tortoise shells lined the roads and clustered about buildings. A few apparently hibernated ones were seen at the Marin-Sierra Camp, near 5000 ft., and at Castle Peak, 7200 ft. On 24 May an enormous migration was observed beginning at 0930 hours, 4.5 mi. E Baxter (ca. 5400 ft.) and continuing for two miles of highway. The butterflies crossed the highway from S to N and moved generally upslope, passing at a rate of one every 5-10 seconds mostly from 3-10 feet above the ground. The migration did not reach to Castle Peak. Only a few live individuals were seen when we returned to the area at 1600 hours. Tortoise shells were abundant up to 7200 feet on 31 May and 7 June, but at much lower densities than observed on 24 May. At 5000 feet they disappeared entirely from 13 June-3 August. From
3 August through 27 October they were continuously present again, but generally at low density. A movement occurred on 29 September when about 80 were observed moving downslope, E to W along 1-80, flying into a strong headwind. These again appeared fresh.
At 7200 ft. tortoise shells were seen every week from 17 May-4 October and again on 23 October. The first fresh specimens were observed on 30 June and thousands flew on 21 and 28 July. These seemed to be in local concentrations, mostly around towns, and no definite directional movement was noted. There were virtually none at this elevation on 3 August, when the species reappeared lower down. On 29 September about 110 were seen at Boreal Ridge, mostly moving downslope and westerly along 1-80, and a few were seen at Donner Pass.
In the valley, N. californica was observed around Sacramento on 11 and 25 September and 6 October. The first autumn sighting at Davis was on 3 October. Thereafter a few were seen each week through 23 October, and scattered sightings were made during the weeks of 13 and 20 November and 11 and 18 December. The bulk of records shifted from east Yolo Co. across the valley toward Vacaville and Dixon through the month of October.
Tortoise shells began flying in the canyons of the Vacas the last week of January 1973. Scattered worn individuals were noted throughout the valley from Winters to Sacramento beginning the second week of March.
In summary, the seasonal changes in distribution of the California tortoise shell in central California in 1972 were:
—A small flight of worn butterflies in the Vacas and valley and in the Sierra foothills in March.
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—A large flight of fresh butterflies in the Vacas in mid-May, followed by a mass movement from W to E across the valley floor in late May depopulating the Vacas for the rest of the season.
—A large flight of fresh butterflies at 4000 feet in the Sierras in mid-May, developing into a huge upslope migration in late May, disappearing in early June.
—A large flight at 7000 feet in late July, disappearing in early August. Fresh butterflies, but no directional movement noted; concentrations local.
—A small to moderate downslope migration at both 5000 and 7000 ft. on 29 September, with scattered records of an autumn flight from late August through late October.
—A small flight in the valley from mid-September into mid-December, mostly in October, with an east-to-west drift, presumably accounting for the spring 1973 butterflies in the Vacas.
Over-all, these records suggest that the California tortoise shell migrated eastward and upslope in spring, and westward and downslope in fall. If we do not postulate estivation or adult diapause, the generation sequence would be about as follows: a brood of new adults, progeny of hibernators, emerged in May in both the Vacas and Sierra foothills. The Vaca insects moved eastward across the valley floor (where N. califomica does not breed, there being no Ceanothus) en masse in mid-May, while their Sierran counterparts moved upslope en masse at the same time. The two currents probably fused. The progeny of these insects emerged in July-August, with no well-defined migration, but perhaps a downward drift. The surge of butterflies moving downslope at the end of September may have represented a third, markedly smaller, generation. These would be the butterflies which appeared at low elevations at low densities and drifted across the valley floor in October. On this schedule each "brood" would take about eight weeks. (Generations of Milbert's tortoise shell, N. milberti Latreille, take about seven weeks in New York.)
During the 24 May eruption I examined 189 freshly killed specimens (103 females). The females were all pre-reproductive, with no mature ova but substantial fat bodies. Of 35 examined for spermatophores, 32 were virgins. Only 11 females of the late July surge were collected, but all were also pre-reproductive. So, too, were 16 collected in the 29 September surge. On the other hand, most of the females collected between the big flights, when the species was at low density, were gravid and/or contained spermatophores, at least until early September.
The brood sequence of N. calif omica is extremely obscure. In the complete absence of reports or observations of larval outbreaks in 1972 the number of generations can only be inferred from the condition of the adults. Although the data strongly suggest three broods, they do not rule out the possibility of only one—emerging in May, summering in the high Sierras, with only sporadic reproduction, and returning downslope to hibernate. Nymphaline adults are capable of extended periods of inactivity, but the reason for large-scale activity at eight-week intervals can only be described as arcane. Alternatively, one can postulate two "populations" in the Sierra, one resident and breeding without migration, one migratory and perhaps not breeding at all.
Clearly, while the generalized picture Powell presents of a species erupting at irregular intervals from persistent epicenters (e.g. Mount Shasta) is broadly accurate, there were unexpected elements of regularity in the 1972 movements whatever the brood sequence that produced them. Following the 1971 outbreak N. calif omica appears to have colonized an extensive area and to have set up a migratory pattern which is seasonally adaptive. To judge by past history, its occupation of these areas will be temporary. The 1972 data raise some interesting questions: is it typical of mass movements that the females are not in reproductive condition? And how quickly do they come into condition? If females do not mate until after the migration, the chances of outbreeding are substantially increased—a possible genetic rationalization of eruptive periodicity (Brown 1957, Quart. Rev. Biol. 32: 247-279).
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Journal of the Lepidopterists' Society
Collections were made with the help of Dr. E. W. Jameson, Jr. and Mr. Allen Allison, both of the Department of Zoology, University of California, Davis, and Mrs. Adrienne R. Shapiro.
Arthur M. Shapiro, Department of Zoology, University of California, Davis, California 95616.
PH1LOTES RITA (LYCAENIDAE) IN A SANDSTORM
Between 0730 and 0810 MST, on an overcast day, 4 September 1970 (at 10 road mi. NE of Goblin Valley turnoff from Hwy. 24, on Hwy. 24, Green River Desert, Emery Co., Utah), Scott Ellis and I encountered Philotes rita Barnes & McDunnough spp. during a strong windstorm. We collected 19 rita clinging to stiff Ephedra plants in ca. 30-40 mph winds. The winds at first were calmer with no blowing sand but soon a gusty sandstorm from the SW hit with fine sand particles. Other plants in the area, including Eriogonum leptocladon Torr. & Gray var. leptocladon, ritas foodplant here, were not nearly as upright in the wind as the Ephedra. Most of the rita perched in a head-down position (3-4 head-up) on the uppermost parts of the Ephedra, with the primaries tucked inside the secondaries, directed away from the wind's angle, and buffeted by the wind. They clung on by their legs wrapped partway around a stem. When approached or disturbed, some flopped down into the plant or onto the ground with the wind (they were still alert). These rita have been genitalically determined and represent an unnamed subspecies to be described elsewhere.
Oakley Shields, Department of Entomology, University of California, Davis, California 95616.
NOTES AND NEWS
Recent Letters Dear Dr. Sargent:
In the last issue of the "Journal of the Lepidopterists' Society" (Vol. 27, No. 3, 10 August 1973, p. 210-219), there is an interesting study about the Biology of Prepona omphale octavia Fruhstorfer, by Alberto Muyshondt, of San Salvador, C.A., presented "as this is the first time the life cycle of P. omphale octavia is fully described, . . . ." However, it is necessary to note that I published a long time ago (1933), about the same species and surely the same subspecies, because the names of E. Le Moult (1932-33), in my opinion are subject to critical study and revision, in Guatemala occidental (Department of Quezaltenango).
I am sorry I cannot send you a reprint of my work because I have only one in my library. The entire reference of this study is: Novitates Entomologicae. Paris. Fasc. 3-4, 30 dec. 1933, p. 24-26, 1 pi. couleurs. "Observations biologiques sur les differents etats de Prepona omphale guatemalensis Le Moult (Lep. Nymphalidae) par Rene Lichy." Also in: Nov. Entom., Janvier 1932, 2e. annee No. 1, ler. supplement, p. 11, pi. couleurs. About the species, subspecies and aberrations described by E. Le Moult, cf. collection of "Nov. Entom."
I send this notice to you for the next "Journal." Thank you very much. Very best wishes.
Yours sincerely,
Rene Lichy
"Yavita"
Chemin des Claies
F-95320 Saint Leu-La Foret
France