NNOTATED CHECKLIST OF THE 
UTTERFLIES OF ILLINOIS 
Ittnors has undergone a vast amount of ecological 
ange since its settlement, and the pace of this change 
s accelerated in recent years. Change has taken sev- 
41 forms—in agriculture and industry, in metropolitan 
sas, in highway development, and in the clearing of 
id for residential subdivisions and shopping centers. 
1e widespread use of chemical insecticides and herbi- 
les is also strongly suspected of having contributed to 
logical change, and in particular, a decline in but- 
fly populations. 
By the 1860's, when continuous butterfly collecting 
yan in Illinois, agricultural development of the state 
s already well advanced, and thus it is difficult to 
ess its effect on the original butterfly fauna. The other 
anges are more recent. We believe that at least three 
tterflies have been extirpated within Illinois. On the 
ier hand, some species have been added to the Illi- 
is butterfly fauna. 
Ecological succession, a concept well discussed by 
apiro (1966), and in many cases a result of man’s 
eration of his environment, is discernible in localities 
ich have been studied for many years. At Streator, La 
lle County, where Irwin collected for more than 30 
ws, a species once locally common, Anaea andria, is 
w rare and has not been taken since 1955, while 
losyne gorgone, not found there at all until 1964, 
ickly became abundant. 
With the increasingly destructive alteration of the 
vironment by man, it becomes ever more important 
record conditions as they now exist and to document 
record by the collecting and proper deposition of 
cimens wherever possible. This is the principal ob- 
tive of this study. 
The present survey of Illinois butterflies beean in 
92, when Downey canvassed the Illinois members of 
' Lepidopterists’ Society, seeking distributional data 
Illinois Lycaenidae (Downey 1966). The encourag- 
response by Illinois lepidopterists led the authors to 
and the survey to include all of the 146 butterfly 
cies that presently occur in the state. 
This report is a distributional study, not a manual 
the identification of Illinois butterflies. Little de- 
iptive material is included, and then only if the TIli- 
‘ population of a species presents special problems not 
cussed in popular butterfly manuals. One of the 
st widely used manuals is Klots’ field guide (1951), 
1 we recommend that it be used in conjunction with 
‘publication. Nearly all listed species are illustrated 
this guide by Klots, and, for convenience, references 
1S work are given in the svnonymies. Klots men- 
ied Illinois in the ranges of several species for which 
es 
Th Paper is printed by authority of the State of Illinois, IRS Ch. 
rhe 98.12. It 1s a contribution from the Section of Faunistic Surveys 
“nsect Identification of the Illinois Natural Histo Survey. Roderick 
rete 1s a Research Affiliate of the Survey, and Henares Curator of 
iden Illinois State Museum. Dr. John C. Downey is Head of the 
tment of Biology at the University of Northern Iowa. 
Roderick R. Irwin and John C. Downey 
there appear to be no Illinois records. Unfortunately, 
he was unable to locate notes used in the preparation of 
the field guide in order to support his statements. 
At first glance, it might appear that the butterfly 
fauna of Illinois is relatively uninteresting. However, 
the great length of the state from north to south and 
the presence within its borders of three life zones (Mer- 
riam 1894), permit establishment of more widely diverse 
faunae than in most other states. Many Illinois butter- 
flies are statewide in distribution. Transition and even 
Canadian Zone species such as Speyeria atlantis, Poly- 
gonia faunus, and Nymphalis vau-album j-album occur 
in extreme northern Illinois. At the southern extremity 
of the state we find butterfles of distinctly Lower Austral 
affinities. Some of them are infrequent, e.g. Aflides 
halesus, whereas others are relatively frequent. 
The apparent absence of many species in some sec- 
tions of the state, particularly the northwestern counties, 
is an illusion created by lack of intensive collecting. The 
most concentrated collecting in Illinois has been in the 
Chicago area, where many lepidopterists live. The south- 
ern tier of counties has also had relatively good collecting 
coverage. 
METHODS 
Our data are presented in the form of an annotated 
checklist. The scientific name of the species is followed 
by its common name according to Klots (1951). The 
synonymy is not intended to be complete but includes 
a reference to the original description and type-locality, 
references to names preoccupied or cited in error (desig- 
nated by double dagger), and references to Worthing- 
ton (1880), Holland (1931), Klots (1951), and dos Pas- 
sos (1964, 1969a, 1970). We also include references to 
widely used synonyms not included in the other citations. 
Early authors used the term “in Indiis? indiscrimi- 
nately to indicate the habitat of species which they de- 
scribed from either the East or West Indies. We consider 
this term to refer to the West Indies when it applies 
to Illinois butterflies. 
The distribution of each species known in Illinois 
from more than six localities is illustrated by a map. In- 
dividual records, listed alphabetically by counties, are 
given for species known from six or fewer localities. 
No distinction has been made between records based 
on specimens actually examined by the authors and those 
submitted by collaborators or obtained from the litera- 
ture. All of the latter were carefully evaluated before 
being accepted, and those which appeared at all ques- 
tionable were checked by examination of the specimens 
involved; where this was not possible, the records were 
not used. Critical determinations were made by special- 
ists studying particular butterfly groups. 
In some areas, due to the number and closeness of 
localities, two or even three nearly adjoining localities 
