Hops Azure - Celastrina humulus
[From Scott and Wright 1998; Opler and Wright 1999; Glassberg 2001] Forewing about 1.0-1.3 cm. Uppersurface of male powdery blue, female blue basally, suffused with varying amounts of white scaling, with extensive black on coastal and outer region of forewing and coastal region of hindwing. Undersurface white with small submarginal black marks surrounded by pale halos and capped with chevrons pointing inward, other spots scattered basally varying from almost absent (some females) to heavily marked (some males).
One flight; late May to late July (depending on year), peak flight in June (Scott and Wright 1998). June and July (Glassberg 2001).
Best determined by flight date and close proximity to host plant (hops). Helpful external features include uppersurface of female iridescent blue suffused with varying amounts of white scaling, undersurface white with small submarginal black marks surrounded by pale halos and capped with chevrons pointing inward, other spots scattered basally varying from almost absent to heavily marked.
Possibly endemic to Colorado, from Wyoming border south along eastern slope of Front Range foothills to Colorado Springs area (Scott and Wright 1998; Opler and Wright 1999; Puntenney and Schorr 2016); 1737 m to 2438 m elevation in Colorado (Scott and Wright 1998). Not reported from Wyoming. Not reported from Montana until species formally described in 1998 (Kohler 1980; Stanford and Opler 1993); reported since then (some reports retrospective) from five counties (Carbon, Lewis and Clark, Stillwater, Sweet Grass, Yellowstone), most recently in late June 2008 (FLMNH Lepidopterists' Society database). Range considered by most authorities as restricted to Colorado; Montana reports need reevaluation. Locally common (Glassberg 2001).
Foothill canyon bottoms, rockslides, talus slopes, wooded and shrubby riparian floodplains; localized and near larval host plant (Scott and Wright 1998; Opler and Wright 1999; Glassberg 2001; Puntenney and Schorr 2016). Habitat not described for Montana, but probably similar if reports valid.
Larval food plant is Humulus lupulus (for the hops race) or Lupinus argenteus (for the lupine race); Trifolium repens and Verbascum thapsus also reported occasionally for the lupine race (Scott 1992, 2006; Scott and Wright 1998). Adults feed on flower nectar (including Apocynum, Barbarea, Ceanothus, Cerastium, Claytonia, Euphorbia, Geranium, Jamesia, Linum, Phacelia, Prunus, Rhus, Solidago), mud, dung, leafhopper honeydew (Scott and Wright 1998; Opler and Wright 1999; Scott 2014).
Females lay eggs singly or in pairs on host plant flower buds (mostly male flowers). Eggs hatch in 5 days, larvae remain on host plant after egg-hatch, feed on flower buds and flowers, pupate on underside of host plant leaf; pupae overwinter (hibernate). In captivity, adults eclose (emerge from pupa) in 9-30 days (mean = 21 days) after exposure to late-spring temperture. Larvae tended by ants (Formica podzolica and Tapinoma sessile) in Colorado (Scott 1992, 2006; Scott and Wright 1998). Males patrol throughout the day in gulches near host plant (up to 100 m from host plant) while searching for females (Scott and Wright 1998).
- Literature Cited AboveLegend: View Online Publication
- Glassberg, J. 2001. Butterflies through Binoculars: A Field Guide to the Butterflies of Western North America. Oxford University Press.
- Kohler, S. 1980. Checklist of Montana Butterflies (Rhopalocera). Journal of the Lepidopterists' Society 34(1): 1-19.
- Opler, P.A. and A.B. Wright. 1999. A field guide to western butterflies. Second edition. Peterson Field Guides. Houghton Mifflin Company, Boston, Massachusetts. 540 pp.
- Puntenney, C.P. and R.A. Schorr. 2016. Patch occupancy and habitat of the Hops Azure (Celastrina humulus), a rare North American endemic butterfly: insights for monitoring and conservation. Journal of Insect Conservation. 20: 215-222.
- Scott, J.A. 1992. Hostplant records for butterflies and skippers (mostly from Colorado) 1959-1992, with new life histories and notes on oviposition, immatures, and ecology. Papilio new series #6. 185 p.
- Scott, J.A. 2006. Butterfly hostplant records, 1992-2005, with a treatise on the evolution of Erynnis, and a note on new terminology for mate-locating behavior. Papilio new series #14. 74 p.
- Scott, J.A. 2014. Lepidoptera of North America 13. Flower visitation by Colorado butterflies (40,615 records) with a review of the literature on pollination of Colorado plants and butterfly attraction (Lepidoptera: Hersperioidea and Papilionoidea). Contributions of the C.P. Gillette Museum of Arthopod Diversity. Fort Collins, CO: Colorado State University. 190 p.
- Scott, J.A. and D.M. Wright. 1998. A new Celastrina from the eastern slope of Colorado. Papilio new series #9. 15 p.
- Stanford, R.E. and P.A. Opler. 1993. Atlas of western USA butterflies: including adjacent parts of Canada and Mexico. Unpubl. Report. Denver and Fort Collins, Colorado 275 pp.
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