Montana Field Guide

The following is taken from Ferris and Brown (1981), Scott (1986), Opler and Wright (1999), Glassberg (2001), and Pyle (2002). Large Marble butterflies are medium-sized with a wing span of 3.75-5 mm (1.5-2 inches). From the top (dorsal), their front wings are white with dark green patterning near the tips. The top of the hindwing can be greenish-yellow for females and white with grey patterning for males. Underneath (ventral), their hindwing is distinctive; the white background has green patterning with yellow veins. The yellow veins separate this species from other closely related marble species.

Caterpillars have short, sparse setae (insect hair), and have yellow and green strips that extend the length of their body, and small black spots. Eggs are white ovals with ridges extending longitudinally. Their cocoon (chrysalis) is long and slender, pointed at the ends, tan in color, has ridges along the length and camouflaged to blend into the environment.

The following comes from Emmel (1964), Scott and Scott (1978), Scott (1986), Scott and Epstein (1987), Glassberg (2001), Guppy and Shepard (2001), Pyle (2002), and Warren (2005). Large Marble have one generation per year in the northern parts of their range (Alaska; adults observed in May through July) and two generations in the southern portion of their range (California; adults observed in February to April and in May to August). Females lay a single egg on a mustard flower. The developing caterpillars eat the flowers and fruits. Large Marbles overwinter as chrysalids and emerge as adults the following spring or summer (Butterflies and Moths of North America).

Best determined by a combination of creamy-white color, forewing with a black-patterned apex encompassing a circular white spot along costa, narrow black bar in forewing cell with scattered white scales in middle; undersurface of forewing with some yellow-green marbling at apex, hindwing with veins noticeably yellower than complex green marbling.

Non-migratory; adult straight-line movements average less than 500m but may reach several kilometers (Scott 1975a, 1975c, 1986).

Mustards (Brassicaceae spp.) are the host plant for Large Marble butterflies. Adult butterflies are observed in valleys, hillsides, fields and meadows in a variety of habitats. Predictive distribution modeling in the petition based on observations indicated that mountainous areas had better habitat for Large Marbles (Burls et al. 2023). Males follow streams to look for females during breeding (Scott 1975, and Back et al. 2011). Large Marbles were observed in transition areas and mesic montane meadows in Glacier National Park, Montana (Debinski 1993) and open forest, fields, and meadows in the Greater Yellowstone Ecosystem (Debinski and Pritchard 2002).

Larval food plants include native and exotic species such as Arabis (several species), Barbarea, Brassica (several species), Descurainia, Draba, Erysimum, Hirschfeldia, Isatis, Lepidium, Raphanus, Schoencrambe, Sinapis, Sisymbrium (multiple species), and Thelypodium (Opler 1974, Ferris and Brown 1981, Scott 1986, 1992, 2006, Guppy and Shepard 2001, Graves and Shapiro 2003, Pyle 2002, and Warren 2005). Adults feed on flower nectar (including Achillea, Alcea, Amsinckia, Arabis, Arnica, Barbarea, Berberis, Brassica, Brodiaea, Calochortus, Cardamine, Cerastium, Cirsium, Draba, Erodium, Erysimum, Eschscholzia, Heterotheca, Lesquerella, Mertensia, Plantago, Potentilla, Prunus, Ranunculus, Raphanus, Rubus, Senecio, Sisrinchium, Taraxacum, Thlaspi, Townsendia, Trifolium, Wyethia) and mud (Pyle 2002, James and Nunnallee 2011, and Scott 2014).

Females lay eggs individually on host plant flower buds and inflorescences, rarely on leaves (Opler 1974, Scott 1986, 1992, 2006, and James and Nunnallee 2011). The number of eggs per ovariole (1/8 of total) is about 70 (Ehrlich and Ehrlich 1978). Eggs hatch in about 4 days, develop from L1 instar to L5 instar and pupate in another 18 days (depending on temperature). Larvae are solitary, feed on all parts of host plant, rest among flower clusters, and build no nest (Scott 1986, and James and Nunnallee 2011). Overwinter (diapause) as pupae, usually on host plant (Opler 1974, Scott 1979, 1986, and James and Nunnallee 2011), adults eclose (emerge from pupae) in spring if from an overwintering cohort. Males patrol throughout the day in open areas and valley bottoms in search of females (Scott 1975b, 1986).