Butterflies Flying in Colorado in September (60 Species)

60 butterflies were recorded flying in Colorado in September in our iNaturalist sample; 12 of the top 50 are at their peak this month. The list is ranked by number of research-grade observations.

Mar Apr May Jun Jul Aug Sep Oct Nov

Top butterflies in September

Painted Lady1,130 obs.

Monarch892 obs.

Common Checkered-Skipper513 obs.

Small White297 obs.

Dainty Sulphur268 obs.

Gray Hairstreak243 obs.

Variegated Fritillary221 obs.

Common Buckeye209 obs.

Orange Sulphur204 obs.

Western Pygmy-Blue199 obs.

Two-tailed Swallowtail154 obs.

Reakirt's Blue154 obs.

All butterflies flying in Colorado in September

#	Species	Scientific name	Family	Obs.	Peak in state
1	Painted Lady	Vanessa cardui	Brush-footed Butterflies	1,130	Sep (peak)
2	Monarch	Danaus plexippus	Brush-footed Butterflies	892	Sep (peak)
3	Common Checkered-Skipper	Burnsius communis	Skippers	513	Aug (past peak)
4	Small White	Pieris rapae	Whites, Yellows, and Sulphurs	297	Jul (past peak)
5	Dainty Sulphur	Nathalis iole	Whites, Yellows, and Sulphurs	268	Oct (rising)
6	Gray Hairstreak	Strymon melinus	Gossamer-winged Butterflies	243	Aug (past peak)
7	Variegated Fritillary	Euptoieta claudia	Brush-footed Butterflies	221	Jul (past peak)
8	Common Buckeye	Junonia coenia	Brush-footed Butterflies	209	Oct (rising)
9	Orange Sulphur	Colias eurytheme	Whites, Yellows, and Sulphurs	204	Jul (past peak)
10	Western Pygmy-Blue	Brephidium exilis	Gossamer-winged Butterflies	199	Sep (peak)
11	Two-tailed Swallowtail	Papilio multicaudata	Swallowtails and Parnassians	154	Jul (past peak)
12	Reakirt's Blue	Echinargus isola	Gossamer-winged Butterflies	154	Jul (past peak)
13	Hoary Comma	Polygonia gracilis	Brush-footed Butterflies	152	Jul (past peak)
14	Checkered White	Pontia protodice	Whites, Yellows, and Sulphurs	142	Jul (past peak)
15	Marine Blue	Leptotes marina	Gossamer-winged Butterflies	141	Sep (peak)
16	Field Crescent	Phyciodes pulchella	Brush-footed Butterflies	135	May (past peak)
17	Mourning Cloak	Nymphalis antiopa	Brush-footed Butterflies	130	Apr (past peak)
18	Rocky Mountain Parnassian	Parnassius smintheus	Swallowtails and Parnassians	127	Jul (past peak)
19	Red Admiral	Vanessa atalanta	Brush-footed Butterflies	120	Jun (past peak)
20	American Branded Skipper	Hesperia colorado	Skippers	117	Aug (past peak)
21	Queen	Danaus gilippus	Brush-footed Butterflies	114	Sep (peak)
22	Woodland Skipper	Ochlodes sylvanoides	Skippers	114	Aug (past peak)
23	Black Swallowtail	Papilio polyxenes	Swallowtails and Parnassians	101	Jul (past peak)
24	Melissa Blue	Plebejus melissa	Gossamer-winged Butterflies	98	Jul (past peak)
25	Mormon Fritillary	Argynnis mormonia	Brush-footed Butterflies	97	Aug (past peak)
26	Purplish Copper	Tharsalea helloides	Gossamer-winged Butterflies	90	Sep (peak)
27	Juba Skipper	Hesperia juba	Skippers	87	May (past peak)
28	Clouded Sulphur	Colias philodice	Whites, Yellows, and Sulphurs	86	Sep (peak)
29	American Lady	Vanessa virginiensis	Brush-footed Butterflies	75	Oct (rising)
30	Viceroy	Limenitis archippus	Brush-footed Butterflies	70	Aug (past peak)
31	Weidemeyer's Admiral	Limenitis weidemeyerii	Brush-footed Butterflies	66	Jul (past peak)
32	Green Comma	Polygonia faunus	Brush-footed Butterflies	49	Aug (past peak)
33	Huron Skipper	Atalopedes huron	Skippers	44	Sep (peak)
34	Aphrodite Fritillary	Argynnis aphrodite	Brush-footed Butterflies	40	Jul (past peak)
35	Milbert's Tortoiseshell	Aglais milberti	Brush-footed Butterflies	39	Jul (past peak)
36	Pearl Crescent	Phyciodes tharos	Brush-footed Butterflies	25	Aug (past peak)
37	Bronze Copper	Tharsalea hyllus	Gossamer-winged Butterflies	24	Sep (peak)
38	Coronis Fritillary	Argynnis coronis	Brush-footed Butterflies	24	Jun (past peak)
39	Gorgone Checkerspot	Chlosyne gorgone	Brush-footed Butterflies	22	Jun (past peak)
40	Pine White	Neophasia menapia	Whites, Yellows, and Sulphurs	21	Aug (past peak)
41	Small Wood-Nymph	Cercyonis oetus	Brush-footed Butterflies	20	Jul (past peak)
42	Peck's Skipper	Polites peckius	Skippers	19	Aug (past peak)
43	Sandhill Skipper	Polites sabuleti	Skippers	17	Sep (peak)
44	Lupine Blue	Icaricia lupini	Gossamer-winged Butterflies	16	Jul (past peak)
45	Greenish Blue	Icaricia saepiolus	Gossamer-winged Butterflies	15	Jul (past peak)
46	Satyr Comma	Polygonia satyrus	Brush-footed Butterflies	14	Jul (past peak)
47	American Snout	Libytheana carinenta	Brush-footed Butterflies	14	Jul (past peak)
48	Fiery Skipper	Hylephila phyleus	Skippers	13	Sep (peak)
49	Arizona Sister	Adelpha eulalia	Brush-footed Butterflies	13	Sep (peak)
50	Hackberry Emperor	Asterocampa celtis	Brush-footed Butterflies	13	Jul (past peak)