Peak Count Data for Butterflies at Fermilab
Sorted by Peak Count per Hour in 2001
A list of butterflies Tom Peterson observed on the 6800 acre Fermilab site, 40 miles west of Chicago, Illinois.
Each time Tom went butterfly watching, he counted the number he saw per hour of each species. At the end of each summer, he made a chart with the day on which he saw the maximum number of each species ("date recorded" below) and the number he saw ("peak count per hour") for that species.

Butterfly Data - Peak Count by Common Name - Scientific Name - by Number Found in 1999 - 2000 - 2001 - 2002 - 2003
Butterfly SpeciesDate RecordedPeak Count
per hour

Cabbage White
Pieris rapae
08/04/200130+ +
Common Wood-Nymph
Cercyonis pegala
07/08/200125  
European Skipper
Thymelicus lineola
06/21/200120+ +
Least Skipper
Ancyloxypha numitor
08/04/200120+ +
Red Admiral
Vanessa atalanta
05/17/200120+ +
Pearl Crescent
Phyciodes tharos
08/24/200119  
Viceroy
Limenitis archippus
08/04/200118  
Eastern Comma
Polygonia comma
08/24/200115  
Black Swallowtail
Papilio polyxenes
08/04/200112  
Dion Skipper
Euphyes dion
07/05/200112  
Clouded Sulphur*
Colias philodice
08/26/2001,
09/11/2001
11  
Great Spangled Fritillary
Speyeria cybele
07/05/200111  
Orange Sulphur*
Colias eurytheme
08/26/2001,
09/11/2001
11  
Monarch
Danaus plexippus
09/11/200110+ +
Painted Lady
Vanessa cardui
08/26/200110  
Question Mark
Polygonia interrogationis
05/29/20019  
Common Buckeye
Junonia coenia
09/11/20017  
Coral Hairstreak
Satyrium titus
06/30/20017  
Silver-Spotted Skipper
Epargyreus clarus
08/26/20017  
American Lady
Vanessa virginiensis
05/17/20015  
Banded Hairstreak
Satyrium calanus
06/25/20015  
Bronze Copper
Lycaena hyllus
08/03/20015  
Meadow Fritillary
Boloria bellona
06/24/2001,
09/02/2001
5  
Purplish Copper
Lycaena helloides
09/11/20015  
Wild Indigo Duskywing
Erynnis baptisiae
09/20/20015  
Eastern Tiger Swallowtail
Papilio glaucus
07/31/20014  
Peck’s Skipper
Polites peckius
06/12/20014  
Red-Spotted Purple
Limenitis arthemis
08/10/20014  
Dun Skipper
Euphyes vestris
07/13/20013  
Spring Azure
Celastrina ladon
08/10/20013  
Black Dash
Euphyes conspicua
07/13/20012  
Delaware Skipper
Anatrytone delaware
07/11/20012  
Eastern Comma
Polygonia comma
09/20/20012  
Gray Comma
Polygonia progne
08/04/20012  
Little Wood-Satyr
Megisto cymela
06/12/20012  
Mourning Cloak
Nymphalis antiopa
05/29/20012  
Tawny-Edged Skipper
Polites themistocles
05/29/20012  
Variegated Fritillary
Euptoieta claudia
08/26/20012  
Acadian Hairstreak
Satyrium acadica
07/08/20011  
American Snout
Libytheana carinenta
09/29/20011  
Checkered White
Pontia protodice
09/05/20011  
Common Sootywing
Pholisora catullus
08/26/20011  
Dainty Sulphur
Nathalis iole
08/24/20011  
Eyed Brown
Satyrodes eurydice
07/08/20011  
Fiery Skipper
Hylephila phyleus
08/26/20011  
Giant Swallowtail
Papilio cresphontes
08/26/20011  
Little Glassywing
Pompeius verna
06/22/20011  
Northern Pearly-Eye
Enodia anthedon
07/08/20011  
Painted Lady
Vanessa cardui
10/06/20011  
*Clouded Sulphur and Orange Sulphur are listed as separate species. Tom Peterson does not do separate counts for them since there are many intermediate-looking forms of them. He combines the data for both and the table above lists the same data for both species.