Peak Count Data for Butterflies at Fermilab
Sorted by Peak Count per Hour in 2002
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

Clouded Sulphur*
Colias philodice
08/25/2002,
09/24/2002
30+ +
Orange Sulphur*
Colias eurytheme
08/25/2002,
09/24/2002
30+ +
Cabbage White
Pieris rapae
08/25/200220+ +
EasternTailed-Blue
Everes comyntas
08/25/200220  
Pearl Crescent
Phyciodes tharos
08/25/200220  
Dion Skipper
Euphyes dion
07/16/200220  
Meadow Fritillary
Boloria bellona
06/28/200215  
Northern Pearly-Eye
Enodia anthedon
07/20/200215  
Common Wood-Nymph
Cercyonis pegala
07/20/200212  
European Skipper
Thymelicus lineola
06/21/200211  
Mourning Cloak
Nymphalis antiopa
04/15/20025  
Red-Spotted Purple
Limenitis arthemis
07/31/20025  
Viceroy
Limenitis archippus
07/20/20025  
Silver-Spotted Skipper
Epargyreus clarus
07/31/20025  
Least Skipper
Ancyloxypha numitor
06/21/20025  
Great Spangled Fritillary
Speyeria cybele
07/03/20024  
Northern Broken-Dash
Wallengrenia egeremet
07/14/20024  
Giant Swallowtail
Papilio cresphontes
08/25/20023  
Eastern Tiger Swallowtail
Papilio glaucus
07/31/20023  
Purplish Copper
Lycaena helloides
08/27/20023  
Coral Hairstreak
Satyrium titus
06/21/20023  
Monarch
Danaus plexippus
10/10/20023  
Wild Indigo Duskywing
Erynnis baptisiae
08/28/20023  
Peck’s Skipper
Polites peckius
06/07/20023  
Delaware Skipper
Anatrytone delaware
07/20/20023  
Black Swallowtail
Papilio polyxenes
07/20/20022  
Spring Azure
Celastrina ladon
07/12/20022  
Question Mark
Polygonia interrogationis
09/08/20022  
Eastern Comma
Polygonia comma
07/14/20022  
Gray Comma
Polygonia progne
07/14/20022  
American Lady
Vanessa virginiensis
05/03/20022  
Common Buckeye
Junonia coenia
09/30/20022  
Fiery Skipper
Hylephila phyleus
09/07/20022  
Black Dash
Euphyes conspicua
07/12/20022  
Little Yellow
Eurema lisa
06/21/20021  
Bronze Copper
Lycaena hyllus
09/11/20021  
Acadian Hairstreak
Satyrium acadica
07/03/20021  
Banded Hairstreak
Satyrium calanus
07/14/20021  
Red Admiral
Vanessa atalanta
06/21/20021  
*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.