Peak Count Data for Butterflies at Fermilab
Sorted by Peak Count per Hour in 2000
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
08/11/200020+ +
Clouded Sulphur*
Colias philodice
09/27/200020+ +
Least Skipper
Ancyloxypha numitor
08/21/200020+ +
Orange Sulphur*
Colias eurytheme
09/27/200020+ +
Common Wood-Nymph
Cercyonis pegala
07/13/200013  
EasternTailed-Blue
Everes comyntas
08/11/200011  
Monarch
Danaus plexippus
09/28/200010+ +
Wild Indigo Duskywing
Erynnis baptisiae
09/09/200010+ +
Viceroy
Limenitis archippus
08/24/200010  
Purplish Copper
Lycaena helloides
09/01/20009  
Pearl Crescent
Phyciodes tharos
07/11/20008  
Peck’s Skipper
Polites peckius
06/07/20006  
European Skipper
Thymelicus lineola
07/03/20006  
Coral Hairstreak
Satyrium titus
07/03/20005  
Spring Azure
Celastrina ladon
08/06/20005  
Great Spangled Fritillary
Speyeria cybele
06/22/20005  
Common Buckeye
Junonia coenia
08/06/20004  
Question Mark
Polygonia interrogationis
06/30/20004  
Eastern Comma
Polygonia comma
08/01/20004  
Eyed Brown
Satyrodes eurydice
06/29/20004  
Northern Pearly-Eye
Enodia anthedon
08/01/20004  
Silver-Spotted Skipper
Epargyreus clarus
06/06/20004  
Tawny-Edged Skipper
Polites themistocles
06/07/20004  
Bronze Copper
Lycaena hyllus
08/07/20003  
Red Admiral
Vanessa atalanta
06/06/20003  
Dun Skipper
Euphyes vestris
08/01/20003  
Black Swallowtail
Papilio polyxenes
08/30/20002  
Banded Hairstreak
Satyrium calanus
06/22/20002  
Delaware Skipper
Anatrytone delaware
07/07/20002  
Black Dash
Euphyes conspicua
07/07/20002  
Fiery Skipper
Hylephila phyleus
09/10/20002  
Eastern Tiger Swallowtail
Papilio glaucus
06/06/20001  
Giant Swallowtail
Papilio cresphontes
07/25/20001  
Red-Spotted Purple
Limenitis arthemis
07/24/20001  
Painted Lady
Vanessa cardui
08/06/20001  
American Lady
Vanessa virginiensis
06/07/20001  
Mourning Cloak
Nymphalis antiopa
06/07/20001  
American Snout
Libytheana carinenta
07/21/20001  
Little Wood-Satyr
Megisto cymela
06/06/20001  
Sachem
Atalopedes campestris
09/10/20001  
Common Checkered-Skipper
Pyrgus communis
07/11/20001  
*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.