Peak Count Data for Butterflies at Fermilab
Sorted by Peak Count per Hour in 1999
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
06/21/199930  
Clouded Sulphur*
Colias philodice
07/06/199919  
Orange Sulphur*
Colias eurytheme
07/06/199919  
EasternTailed-Blue
Everes comyntas
08/10/199915  
European Skipper
Thymelicus lineola
06/21/199912  
Monarch
Danaus plexippus
09/10/199910+ +
Fiery Skipper
Hylephila phyleus
08/16/199910  
Great Spangled Fritillary
Speyeria cybele
06/21/19998  
Common Wood-Nymph
Cercyonis pegala
07/06/19998  
Common Buckeye
Junonia coenia
07/06/19997  
Viceroy
Limenitis archippus
06/22/19996  
Pearl Crescent
Phyciodes tharos
07/22/19996  
Red Admiral
Vanessa atalanta
09/10/19995+ +
Banded Hairstreak
Satyrium calanus
06/21/19995  
Question Mark
Polygonia interrogationis
07/06/19994  
Tawny-Edged Skipper
Polites themistocles
06/06/19994  
Bronze Copper
Lycaena hyllus
06/08/1999,
08/16/1999
3  
Spring Azure
Celastrina ladon
08/10/19993  
Eyed Brown
Satyrodes eurydice
07/06/19993  
Black Swallowtail
Papilio polyxenes
08/17/19992  
Purplish Copper
Lycaena helloides
09/07/19992  
Red-Spotted Purple
Limenitis arthemis
08/10/19992  
Mourning Cloak
Nymphalis antiopa
09/25/19992  
Least Skipper
Ancyloxypha numitor
06/08/19992  
Black Dash
Euphyes conspicua
07/06/19992  
Eastern Tiger Swallowtail
Papilio glaucus
08/10/19991  
Giant Swallowtail
Papilio cresphontes
08/20/19991  
Pipevine Swallowtail
Battus philenor
06/06/19991  
Little Yellow
Eurema lisa
06/08/1999,
07/06/1999
1  
Dainty Sulphur
Nathalis iole
09/15/19991  
Acadian Hairstreak
Satyrium acadica
06/23/19991  
Painted Lady
Vanessa cardui
06/06/19991  
Wild Indigo Duskywing
Erynnis baptisiae
09/03/19991  
Dun Skipper
Euphyes vestris
06/21/19991  
Peck’s Skipper
Polites peckius
09/30/19991  
*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.