Butterflies Flying in Pennsylvania in September (60 Species)

60 butterflies were recorded flying in Pennsylvania in September in our iNaturalist sample; 6 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

Monarch3,772 obs.

Huron Skipper3,345 obs.

Small White1,192 obs.

Eastern Tiger Swallowtail926 obs.

Black Swallowtail924 obs.

Peck's Skipper885 obs.

Pearl Crescent777 obs.

Variegated Fritillary764 obs.

Common Buckeye634 obs.

Eastern Tailed-Blue592 obs.

Silver-spotted Skipper536 obs.

Great Spangled Fritillary523 obs.

All butterflies flying in Pennsylvania in September

#	Species	Scientific name	Family	Obs.	Peak in state
1	Monarch	Danaus plexippus	Brush-footed Butterflies	3,772	Aug (past peak)
2	Huron Skipper	Atalopedes huron	Skippers	3,345	Sep (peak)
3	Small White	Pieris rapae	Whites, Yellows, and Sulphurs	1,192	Jul (past peak)
4	Eastern Tiger Swallowtail	Papilio glaucus	Swallowtails and Parnassians	926	Jul (past peak)
5	Black Swallowtail	Papilio polyxenes	Swallowtails and Parnassians	924	Aug (past peak)
6	Peck's Skipper	Polites peckius	Skippers	885	Aug (past peak)
7	Pearl Crescent	Phyciodes tharos	Brush-footed Butterflies	777	Aug (past peak)
8	Variegated Fritillary	Euptoieta claudia	Brush-footed Butterflies	764	Sep (peak)
9	Common Buckeye	Junonia coenia	Brush-footed Butterflies	634	Sep (peak)
10	Eastern Tailed-Blue	Everes comyntas	Gossamer-winged Butterflies	592	Aug (past peak)
11	Silver-spotted Skipper	Epargyreus clarus	Skippers	536	Aug (past peak)
12	Great Spangled Fritillary	Argynnis cybele	Brush-footed Butterflies	523	Jul (past peak)
13	Spicebush Swallowtail	Papilio troilus	Swallowtails and Parnassians	506	Aug (past peak)
14	Orange Sulphur	Colias eurytheme	Whites, Yellows, and Sulphurs	432	Aug (past peak)
15	Red-banded Hairstreak	Calycopis cecrops	Gossamer-winged Butterflies	303	Aug (past peak)
16	Meadow Fritillary	Boloria bellona	Brush-footed Butterflies	295	Aug (past peak)
17	Gray Hairstreak	Strymon melinus	Gossamer-winged Butterflies	293	Aug (past peak)
18	Red-spotted Admiral	Limenitis arthemis	Brush-footed Butterflies	288	Aug (past peak)
19	Eastern Comma	Polygonia comma	Brush-footed Butterflies	264	Aug (past peak)
20	Painted Lady	Vanessa cardui	Brush-footed Butterflies	245	Aug (past peak)
21	Wild Indigo Duskywing	Erynnis baptisiae	Skippers	218	Aug (past peak)
22	Red Admiral	Vanessa atalanta	Brush-footed Butterflies	209	Jul (past peak)
23	Viceroy	Limenitis archippus	Brush-footed Butterflies	206	Sep (peak)
24	Question Mark	Polygonia interrogationis	Brush-footed Butterflies	194	Jul (past peak)
25	Common Checkered-Skipper	Burnsius communis	Skippers	186	Sep (peak)
26	Least Skipper	Ancyloxypha numitor	Skippers	164	Aug (past peak)
27	Fiery Skipper	Hylephila phyleus	Skippers	163	Oct (rising)
28	Zabulon Skipper	Lon zabulon	Skippers	158	Aug (past peak)
29	Hackberry Emperor	Asterocampa celtis	Brush-footed Butterflies	143	Aug (past peak)
30	Northern Pearly-eye	Lethe anthedon	Brush-footed Butterflies	138	Jul (past peak)
31	Clouded Sulphur	Colias philodice	Whites, Yellows, and Sulphurs	115	Aug (past peak)
32	American Lady	Vanessa virginiensis	Brush-footed Butterflies	104	Jul (past peak)
33	American Copper	Lycaena hypophlaeas	Gossamer-winged Butterflies	92	Jul (past peak)
34	Summer Azure	Celastrina neglecta	Gossamer-winged Butterflies	89	Jul (past peak)
35	Mourning Cloak	Nymphalis antiopa	Brush-footed Butterflies	83	Apr (past peak)
36	Eastern Giant Swallowtail	Heraclides cresphontes	Swallowtails and Parnassians	76	Aug (past peak)
37	Pipevine Swallowtail	Battus philenor	Swallowtails and Parnassians	68	Jul (past peak)
38	Sleepy Orange	Eurema nicippe	Whites, Yellows, and Sulphurs	57	Aug (past peak)
39	Cloudless Sulphur	Phoebis sennae	Whites, Yellows, and Sulphurs	49	Aug (past peak)
40	Common Wood-Nymph	Cercyonis pegala	Brush-footed Butterflies	49	Jul (past peak)
41	White M Hairstreak	Parrhasius m-album	Gossamer-winged Butterflies	47	Aug (past peak)
42	Appalachian Brown	Lethe appalachia	Brush-footed Butterflies	33	Jul (past peak)
43	Bronze Copper	Tharsalea hyllus	Gossamer-winged Butterflies	32	Sep (peak)
44	Horace's Duskywing	Erynnis horatius	Skippers	29	Jul (past peak)
45	Harvester	Feniseca tarquinius	Gossamer-winged Butterflies	27	Jul (past peak)
46	Gray Comma	Polygonia progne	Brush-footed Butterflies	23	Jun (past peak)
47	Zebra Swallowtail	Eurytides marcellus	Swallowtails and Parnassians	17	Jul (past peak)
48	American Snout	Libytheana carinenta	Brush-footed Butterflies	16	Jul (past peak)
49	Common Ringlet	Coenonympha california	Brush-footed Butterflies	16	Jun (past peak)
50	Common Sootywing	Pholisora catullus	Skippers	15	Aug (past peak)