Journal of the Lepidopterists' Society 33(3), 1979, 167-169

A DOCUMENTATION OF BIENNIALISM IN BOLO RIA POLARIS ()l

JOHN H. MASTERS 25711 North Vista Fairways Drive, Valencia, California 91355

ABSTRACT. Captureinoncapture records of Buluria polaris at Churchill, Manitoba over a 46-year times pan provide documentation that the species (at least at Churchill) is biennial, where adults fly only in odd-numbered years.

Biennialism in is that situation where an 's life-cycle takes two years to complete so that imagos are produced only after two years of pre-imaginal development. It may be accompanied by biennial flights when, in a given locality, adults fly only in alternate years (periodical flight); or it may be accompanied by annual flights. Unless biennial flights are involved, biennialism is extremely difficult to perceive in nature without carefully working out the insect's life history. Annual flights may occur when the species is only partially biennial or when two allochronic populations are involved. Docu­ mented cases of regular biennialism are very rare in and heretofore have been confined to two species of moth (Lasiocampa quercus callunae in Europe and Coloradia pandora lindseyi Barnes and Benjamin in North America) and a few species of Satyridae (e.g., macounii Edwards, Felder and Felder, Oeneis jutta Hubner, Erebia claudina Borkhausen, and Erebia ligea Linnaeus). For a review of periodical flight behavior in other insects, see Bulmer (1977). In working on a study of occurring at Churchill, Mani­ toba (Masters, 1971), it became evident to me that polaris stellata (Masters) is biennial at Churchill and since that time, I have accumulated enough data to document this fact rather well. This is the first documentation of periodical biennialism in Nymphalid but­ terflies. It has been suggested, and recent collecting data tends to support the contention, that several other species of Boloria (e.g., B. distincta Gibson and B. chariclea Schneider) and the arctic popula­ tions of one species of Hesperiidae (Hesperia manitoba borealis Lindsey) will also turn out to be biennial. Churchill, Manitoba, since the opening of the Hudson Bay Railroad in 1930, has been a classic arctic collecting locality. Because Churchill has been collected repeatedly for a span of 46 years, it is possible to document the capture and noncapture data for Boloria polaris from

I Originally submitted and ac<:epted for publication in 1971; publication delayed due to manuscript loss in the mail. Revised to incorporate new data. 168 JOURNAL OF THE LEPIDOPTERISTS' SOCIETY

TABLE 1. Captureinoncapture records of Boloria polaris at Churchill, Manitoba.

Expeditions recording Expeditions failing to Boloria polaris record Bolaria polaris 1932 (A. V. Harper) 1933 (A. V. Harper) 1936 (H. E. McClure) 1937 (G. S. Brooks) 1939 (G. S. Brooks) 1939 (B. Wilk) 1940 (G. S. Brooks) 1941 (G. S. Brooks) 1942 (G. S. Brooks) 1943 (G. S. Brooks) 1944 (G. S. Brooks) 1946 (G. S. Brooks) 1947 (T. H. Freeman) 1951 (A. B. Klots & R. D. Bird) 1952 (A. B. Klots & R. D. Bird) 1961 (F. H. & P. W. Chermock) 1963 (F. H. & P. W. Chermock) 19670. A. Ebner)' 1968 (e. S. Quelch) 1969 (A. E. Brower) 19690. H. Masters)2 19700. H. Masters) 1970 (C. McCullough)2 1971 (e. D. Ferris) 1974 (D. Oosting & D. Parshall) 1976 (D. Oosting & D . Parshall) 19780. Troubridge)

I Specimens presumably not taken by Ebner personally, 2 Expeditions in late July and August, too late in th e year to expect to find Bolana polaris.

27 collecting expeditions. These data are tabulated in Table 1. Infor­ mation was gleaned from 14 expeditions to Churchill in odd-num­ bered years; 13 of which recorded B. polaris (only my very short trip in late July 1969 did not). On the other hand, I have documented 13 expeditions to Churchill in even-numbered years, none of which re­ corded B. polaris, even though 12 of them were at the proper time of year. I have also scanned both private and institutional collections for specimens of B. polaris that might have been collected at Churchill in even-numbered years, and have failed to find a single specimen. The evidence is thus conclusive, albeit circumstantial, that Boloria polariS has an odd-year only biennial Right at Churchill. Additional records of Boloria polaris accumulated from other lo­ calities suggest that it is probably biennial everywhere, but may be subject to random geographic alternation of odd-year and even-year broods. These data are summarized in Table 2. Unfortunately, no other region in the arctic has been collected as extensively as Chur­ chill for butterRies, over so long a period, and a comparable docu­ mentation of the biennial Right of B. polaris at any additional locality cannot be made. The collecting reports of the Alaska Lepidoptera VOLUME 33, NUMBER 3 169

TABLE 2. Circumpolar capture records of Boloria polaris, noting year of capture. Records, other than Churchill, based on specimens in the American Museum of Natural History, New York and Carnegie Museum, Pittsburgh.

Locality Odd-year captures Even-year captures

Norway: Maalselvin 1923, 1935, 1937, 1939,1971 Finland 1934, 1936, 1946 Alaska: Eagle Summit & Mt. 1931, 1933, 1955, 1961, McKinley 1969, 1971 Nome 1968 Yukon: Haines Junction 1966, 1968 British Columbia: Atlin & Summit Lake 1930, 1966 Mackenzie: Mackenzie Delta & Coppermine 1942,1966 Keewatin: Baker Lake & Eskimo Point 1952, 1956, 1966, 1968 Manitoba: Churchill 1933, 1937, 1939, 1941, 1943, 1947, 1951, 1961, 1963, 1967, 1969, 1971 Greenland 19571 1922, 1926, 1932, 1958 Baffin Island 1925, 1934 1896, 1954 , One specimen 22 July 1957 by A. T. Washburn.

Survey, over a ten year period (1967-1977) establish reasonably well, however, the biennial flight of the species on Ester and Murphy Domes near Fairbanks, Alaska.

LITERATURE CITED BULMER, M. G. 1977. Periodical insects. Am. Nat. 111: 1099-1117. MASTERS, J. H. 1971. The butterHies of Churchill, Manitoba. Mid-Continent Lepid. Ser. 25: 1-13.