Butterflies Flying in Montana in September (50 Species)

50 butterflies were recorded flying in Montana in September in our iNaturalist sample; 5 of the top 50 are at their peak this month. The list is ranked by number of research-grade observations.

Apr May Jun Jul Aug Sep Oct

Top butterflies in September

California Tortoiseshell152 obs.

Mourning Cloak80 obs.

Green Comma75 obs.

Clouded Sulphur58 obs.

Woodland Skipper53 obs.

Milbert's Tortoiseshell51 obs.

Purplish Copper27 obs.

Two-tailed Swallowtail24 obs.

All butterflies flying in Montana in September

#	Species	Scientific name	Family	Obs.	Peak in state
1	California Tortoiseshell	Nymphalis californica	Brush-footed Butterflies	152	Jul (past peak)
2	Mourning Cloak	Nymphalis antiopa	Brush-footed Butterflies	80	Aug (past peak)
3	Green Comma	Polygonia faunus	Brush-footed Butterflies	75	May (past peak)
4	Clouded Sulphur	Colias philodice	Whites, Yellows, and Sulphurs	58	Aug (past peak)
5	Woodland Skipper	Ochlodes sylvanoides	Skippers	53	Aug (past peak)
6	Milbert's Tortoiseshell	Aglais milberti	Brush-footed Butterflies	51	Jul (past peak)
7	Hoary Comma	Polygonia gracilis	Brush-footed Butterflies	45	Aug (past peak)
8	Small White	Pieris rapae	Whites, Yellows, and Sulphurs	43	Jul (past peak)
9	Painted Lady	Vanessa cardui	Brush-footed Butterflies	42	Jul (past peak)
10	Western White	Pontia occidentalis	Whites, Yellows, and Sulphurs	41	Aug (past peak)
11	Purplish Copper	Tharsalea helloides	Gossamer-winged Butterflies	27	Sep (peak)
12	Two-tailed Swallowtail	Papilio multicaudata	Swallowtails and Parnassians	24	Jul (past peak)
13	Satyr Comma	Polygonia satyrus	Brush-footed Butterflies	23	Aug (past peak)
14	Variegated Fritillary	Euptoieta claudia	Brush-footed Butterflies	21	Aug (past peak)
15	Monarch	Danaus plexippus	Brush-footed Butterflies	20	Aug (past peak)
16	Orange Sulphur	Colias eurytheme	Whites, Yellows, and Sulphurs	20	Jul (past peak)
17	Mormon Fritillary	Argynnis mormonia	Brush-footed Butterflies	20	Aug (past peak)
18	Red Admiral	Vanessa atalanta	Brush-footed Butterflies	18	Aug (past peak)
19	Melissa Blue	Plebejus melissa	Gossamer-winged Butterflies	15	Aug (past peak)
20	West Coast Lady	Vanessa annabella	Brush-footed Butterflies	14	Sep (peak)
21	Pine White	Neophasia menapia	Whites, Yellows, and Sulphurs	13	Aug (past peak)
22	Common Checkered-Skipper	Burnsius communis	Skippers	13	Aug (past peak)
23	Common Wood-Nymph	Cercyonis pegala	Brush-footed Butterflies	11	Jul (past peak)
24	Mylitta Crescent	Phyciodes mylitta	Brush-footed Butterflies	11	Aug (past peak)
25	Great Spangled Fritillary	Argynnis cybele	Brush-footed Butterflies	11	Aug (past peak)
26	Lorquin's Admiral	Limenitis lorquini	Brush-footed Butterflies	9	Jul (past peak)
27	Gray Hairstreak	Strymon melinus	Gossamer-winged Butterflies	9	Jul (past peak)
28	Checkered White	Pontia protodice	Whites, Yellows, and Sulphurs	9	Jul (past peak)
29	Anise Swallowtail	Papilio zelicaon	Swallowtails and Parnassians	7	Jul (past peak)
30	Hydaspe Fritillary	Argynnis hydaspe	Brush-footed Butterflies	7	Aug (past peak)
31	Essex Skipper	Thymelicus lineola	Skippers	6	Jul (past peak)
32	Rocky Mountain Parnassian	Parnassius smintheus	Swallowtails and Parnassians	6	Jul (past peak)
33	Small Wood-Nymph	Cercyonis oetus	Brush-footed Butterflies	5	Jul (past peak)
34	Western Tiger Swallowtail	Papilio rutulus	Swallowtails and Parnassians	4	Jun (past peak)
35	American Lady	Vanessa virginiensis	Brush-footed Butterflies	4	Sep (peak)
36	Blue Copper	Tharsalea heteronea	Gossamer-winged Butterflies	4	Jul (past peak)
37	Gray Comma	Polygonia progne	Brush-footed Butterflies	3	Sep (peak)
38	Juba Skipper	Hesperia juba	Skippers	3	May (past peak)
39	American Branded Skipper	Hesperia colorado	Skippers	2	Jul (past peak)
40	Bronze Copper	Tharsalea hyllus	Gossamer-winged Butterflies	2	Sep (peak)
41	Eastern Comma	Polygonia comma	Brush-footed Butterflies	1	May (past peak)
42	Silvery Blue	Glaucopsyche lygdamus	Gossamer-winged Butterflies	1	Jun (past peak)
43	Canadian Tiger Swallowtail	Papilio canadensis	Swallowtails and Parnassians	1	Jul (past peak)
44	Northern Crescent	Phyciodes cocyta	Brush-footed Butterflies	1	Jul (past peak)
45	Viceroy	Limenitis archippus	Brush-footed Butterflies	1	Jul (past peak)
46	Hedgerow Hairstreak	Satyrium saepium	Gossamer-winged Butterflies	1	Jul (past peak)
47	Sandhill Skipper	Polites sabuleti	Skippers	1	Jul (past peak)
48	Weidemeyer's Admiral	Limenitis weidemeyerii	Brush-footed Butterflies	1	Jul (past peak)
49	Lupine Blue	Icaricia lupini	Gossamer-winged Butterflies	1	Jul (past peak)
50	Aphrodite Fritillary	Argynnis aphrodite	Brush-footed Butterflies	1	Jul (past peak)