Peak Count Data for Butterflies at Fermilab
Sorted by Peak Count per Hour in 2003
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

Meadow Fritillary
Boloria bellona
07/31/200320+ +
Painted Lady
Vanessa cardui
09/17/200320+ +
Common Wood-Nymph
Cercyonis pegala
07/29/200320+ +
Pearl Crescent
Phyciodes tharos
05/13/200320  
Purplish Copper
Lycaena helloides
09/09/200314  
Cabbage White
Pieris rapae
09/06/200312  
Clouded Sulphur*
Colias philodice
10/11/200310  
Great Spangled Fritillary
Speyeria cybele
07/14/200310  
Little Wood-Satyr
Megisto cymela
06/24/200310  
European Skipper
Thymelicus lineola
06/24/200310  
Tawny-Edged Skipper
Polites themistocles
06/07/200310  
Orange Sulphur*
Colias eurytheme
10/11/200310  
Coral Hairstreak
Satyrium titus
07/13/20037  
Eastern Comma
Polygonia comma
04/15/20037  
EasternTailed-Blue
Everes comyntas
07/29/20035  
Eyed Brown
Satyrodes eurydice
07/13/20035  
Monarch
Danaus plexippus
09/06/20035  
Silver-Spotted Skipper
Epargyreus clarus
08/13/20035  
Banded Hairstreak
Satyrium calanus
07/14/20034  
Northern Pearly-Eye
Enodia anthedon
07/14/20034  
Black Swallowtail
Papilio polyxenes
06/25/20033  
Giant Swallowtail
Papilio cresphontes
08/14/20033  
Eastern Tiger Swallowtail
Papilio glaucus
08/10/20033  
Bronze Copper
Lycaena hyllus
07/29/20033  
Mourning Cloak
Nymphalis antiopa
04/15/20033  
Viceroy
Limenitis archippus
07/29/20033  
Wild Indigo Duskywing
Erynnis baptisiae
10/13/20033  
Least Skipper
Ancyloxypha numitor
06/24/20033  
Dion Skipper
Euphyes dion
07/09/20033  
Spring Azure
Celastrina ladon
07/24/20032  
Red Admiral
Vanessa atalanta
07/29/20032  
Peck’s Skipper
Polites peckius
06/20/20032  
Acadian Hairstreak
Satyrium acadica
07/09/20031  
Question Mark
Polygonia interrogationis
06/02/20031  
Gray Comma
Polygonia progne
07/07/20031  
American Lady
Vanessa virginiensis
04/25/20031  
Common Sootywing
Pholisora catullus
06/07/20031  
Delaware Skipper
Anatrytone delaware
07/09/20031  
Black Dash
Euphyes conspicua
07/16/20031  
*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.