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1969
Journal of the Lepidopterists' Society
31
NOTES ON LARVAL HOST ACCEPTANCE IN A CALIFORNIA POPULATION OF PLEBEJUS ACMON (LYCAENIDAE)
Glenn Alan Gorelick
University of California, Berkeley
Plebejus acmon (Westwood and Hewitson) is a well-known blue that ranges from the Pacific Coast to the Great Plains, the various populations within this range varying considerably. The species level status of this species and related entities is still unclear. Downey (1961) points out that P. lupini (Bdv.), P. monticola (Clemence) and P. chlorina (Skinner) have all, at one time or another, been regarded as conspecific with typical P. acmon,
Edwards (1889) states that the larval hostplant for this species is Hosackia, whereas Comstock (1927) and Downey (1961) assert that larvae of the P. acmon group, including P. a. cottlei (Grinnell), feed on Eriogonum, Hosackia, Astragalus, and Lotus. Klots (1951) mentions a fifth genus, Acmispon, but Munz & Keck (1959) place members of the legume genera Hosackia and Acmispon in the genus Lotus.
On May 7, 1967, eight second instar larvae of the common, widespread phenotype of P. acmon were found in the San Bruno Mountains near Colma, San Mateo County, California, skeletonizing the leaves of Eriogonum latifolium latifolium Sm. The larvae varied from grass green to pale pink in contrast to the "dingy yellowish" color reported by Klots (1951). These larvae were observed on the tops and the undersides of the leaves during warm weather and moved towards the stems near the base of the plant when cold temperatures, which are frequent in the San Bruno Mountains, prevailed. In the laboratory the larvae were reared in vials, one larva/vial. The plants listed in Table 1 were used as hosts.
The larvae fed on all of the listed plants except leaves of Melilotus indi-cus, although two of four died after feeding on Eriogonum latifolium latifolium. The flowers of Eriogonum species were accepted as readily as the leaves and are known to be used in the field later in the season (Opler, 1968). Five of the eight larvae pupated between May 18 and 26 and the adults emerged between May 27 and June 1. Later field observations confirmed that the females visited the leaves of E. I. latifolium, where the eggs were presumably deposited. Although most of the plants were not yet (as of May 7) in bloom, the larvae devoured the flowers of this plant taken from other areas of the San Bruno Mountains.
It is probable that Plebejus acmon has several broods in the San Bruno Mountains, larvae of the spring brood feeding on the leaves and larvae of
32 Gorelick: Hostplant acceptance by acmon Vol. 23, no. 1
Table 1. Host plant acceptance by second instar larvae of
Plebejus acmon
No. of Plant Larvae Remarks
Leguminosae:
1. Lotus scoparius Ottley 2 Both accepted plant readily—one (leaves) placed on Eriogonum fasciculatum
foliolosum for final three days; other fed until pupation (V-18)
2. Trifolium obtusiflorum Hook. 1 Fed until pupation (V-26) (flowers)
3. Melilotus indicus ( L.) 1 No feeding occurred—died after three (leaves) days
Polygonaceae:
4. Eriogonum latifolium latifolium Sm. 4 All accepted it readily—two died and (leaves and flowers) two fed until pupation (V-22 and V-25)
5. Eriogonum fasciculatum var. 1 Last instar transferred from Lotus sco-foliolosum (Nutt.) S. Stokes parius, fed for three days until ma-(leaves and flowers) turity (pupated V-18)
succeeding broods feeding on the flowers after the leaves have curled and hardened. Further evidence for the lack of host specificity by P. acmon was suggested by the ability of the larvae to feed on Trifolium (clover) in the laboratory, although this was not observed in the field. The large number of buckwheats and legumes available to females of P. acmon might explain its wide distribution. Further work on hostplant selection and morphology, behavior and host specificity of the larvae as well may help clarify the nomenclature within the P. acmon complex.
My sincere thanks go to Wayne Gagne and J. A. Powell, of the University of California, Berkeley, for advice and assistance and critical review in preparation of the manuscript.
Literature Cited
Comstock, J. A., 1927. Butterflies of California. Published bv author, Los Angeles.
334 pp., 63 pis. Downey, J. C, 1961, in: Ehrlich and Ehrlich. How to know the butterflies. W. C.
Brown & Co., Dubuque, Iowa, pp. 228-242. Edwards, H., 1889. Bibliographical catalogue of the described transformations of the
North American Lepidoptera. Bull. U.S. Natl. Mus., 35: 1-37. Klots, A. B., 1951. A field guide to the butterflies of North. America, east of the
Great Plains. Houghton-Mifflin Co., Boston, Mass., 349 pp., 40 pis. Munz, P. A. & D. D. Keck, 1959. A California flora. University of California Press,
Berkeley and Los Angeles, 1681 pp. Opler, P. A., 1968. Myrmecophily reported for Icaricia acmon and Philotes enoptes
bayensis (Lepidoptera: Lycaenidae), in: Proc. Pac. Coast Ent. Soc, Pan-Pac.
Ent., 44(1): 79-80.