| Species | Latin Name | Numbers | Sightings | First | Last |
|---|---|---|---|---|---|
| Acadian Hairstreak | Satyrium acadica | 11 | 7 | 6/20/98 | 7/11/98 |
| Alfalfa Butterfly | Colias eurytheme | 583 | 60 | 6/28/98 | 12/2/98 |
| American Copper | Lycaena phlaeas americana | 162 | 43 | 5/10/98 | 10/17/98 |
| American Painted Lady | Vanessa virginiensis | 85 | 51 | 5/3/98 | 10/17/98 |
| American Snout | Libytheana carinenta | 2 | 2 | 7/17/98 | 9/1/98 |
| Aphrodite | Speyeria aphrodite | 21 | 9 | 6/28/98 | 9/19/98 |
| Appalachian Eyed Brown | Satyrodes appalachia | 50 | 17 | 6/20/98 | 8/1/98 |
| Baltimore | Euphydryas phaeton | 104 | 17 | 6/16/98 | 7/5/98 |
| Banded Hairstreak | Satyrium calanus | 35 | 15 | 6/18/98 | 7/25/98 |
| Black Dash | Euphyes conspicua | 27 | 8 | 6/20/98 | 7/25/98 |
| Black Swallowtail | Papilio polyxenes | 84 | 45 | 5/12/98 | 10/6/98 |
| Broad-winged Skipper | Poanes viator | 8 | 4 | 7/5/98 | 7/12/98 |
| Bronze Copper | Lycaena hyllus | 41 | 16 | 7/26/98 | 10/24/98 |
| Brown Elfin | Callophrys augustinus | 5 | 2 | 4/25/98 | 5/6/98 |
| Buckeye | Junonia coenia | 72 | 36 | 7/6/98 | 10/24/98 |
| Cabbage Butterfly | Pieris rapae | 1771 | 272 | 3/30/98 | 10/26/98 |
| Clouded Sulphur | Colias philodice | 2367 | 139 | 5/4/98 | 10/28/98 |
| Comma | Polygonia comma | 70 | 32 | 3/26/98 | 10/12/98 |
| Common Sootywing | Pholisora catullus | 16 | 13 | 5/15/98 | 8/29/98 |
| Compton's Tortoise Shell | Nymphalis vaualbum | 5 | 3 | 4/12/98 | 4/28/98 |
| Coral Hairstreak | Satyrium titus | 10 | 6 | 6/20/98 | 7/5/98 |
| Crossline Skipper | Polites origenes | 12 | 9 | 6/20/98 | 8/14/98 |
| Delaware Skipper | Anatrytone logan | 52 | 23 | 6/20/98 | 9/19/98 |
| Dion Skipper | Euphyes dion | 14 | 10 | 6/28/98 | 8/1/98 |
| Dorcas Copper | Lycaena dorcas | 154 | 2 | 7/4/98 | 7/12/98 |
| Dreamy Duskywing | Erynnis icelus | 31 | 12 | 5/9/98 | 5/29/98 |
| Dukes Skipper | Euphyes dukesi | 4 | 2 | 7/19/98 | 7/26/98 |
| Dun Skipper | Euphyes vestris | 66 | 32 | 6/20/98 | 8/13/98 |
| Eastern-tailed Blue | Everes comyntas | 440 | 79 | 5/14/98 | 10/24/98 |
| Edward's Hairstreak | Satyrium edwardsii | 12 | 3 | 6/21/98 | 7/4/98 |
| Erynnis Species | Erynnis genus (unidentified) | 35 | 8 | 5/7/98 | 8/7/98 |
| European Skipper | Thymelicus lineola | 785 | 51 | 5/19/98 | 7/17/98 |
| Eyed Brown | Satyrodes eurydice | 39 | 18 | 6/1/98 | 7/7/98 |
| Fiery Skipper | Hylephilia phyleus | 49 | 21 | 7/11/98 | 10/24/98 |
| Giant Swallowtail | Papilio cresphontes | 34 | 27 | 5/15/98 | 8/16/98 |
| Great Spangled Fritillary | Speyeria cybele | 457 | 90 | 5/20/98 | 9/19/98 |
| Gulf Fritillary | Agraulis vanillae | 1 | 1 | 7/21/98 | 7/21/98 |
| Hackberry Butterfly | Asterocampa celtis | 6 | 4 | 6/21/98 | 7/12/98 |
| Harris' Checkerspot | Chlosyne harrisii | 2 | 1 | 6/7/98 | 6/7/98 |
| Harvester | Feniseca tarquinius | 9 | 6 | 5/7/98 | 9/16/98 |
| Hickory Hairstreak | Satyrium caryaevorum | 3 | 3 | 6/20/98 | 7/17/98 |
| Hoary Edge | Achalarus lyciades | 3 | 2 | 5/27/98 | 5/30/98 |
| Hobomok's Skipper | Poanes hobomok | 154 | 41 | 5/12/98 | 6/18/98 |
| Horace Duskywing | Erynnis horatius | 20 | 7 | 6/28/98 | 9/11/98 |
| Juvenal's Duskywing | Erynnis juvenalis | 44 | 25 | 5/5/98 | 6/7/98 |
| Least Skipper | Ancyloxypha numitor | 138 | 34 | 5/31/98 | 9/27/98 |
| Leonard's Skipper | Hesperia leonardus | 33 | 11 | 8/15/98 | 9/19/98 |
| Little Glassywing | Pompeius verna | 17 | 11 | 6/27/98 | 7/19/98 |
| Little Wood Satyr | Megisto cymela | 437 | 67 | 5/16/98 | 7/18/98 |
| Little Yellow | Eurema lisa | 60 | 24 | 5/31/98 | 10/24/98 |
| Long Dash | Polites mystic | 16 | 11 | 5/21/98 | 6/20/98 |
| Meadow Fritillary | Boloria bellona | 12 | 9 | 5/14/98 | 9/26/98 |
| Milbert's Tortoise Shell | Nymphalis milberti | 86 | 28 | 4/11/98 | 9/26/98 |
| Monarch | Danaus plexippus | 255 | 84 | 6/8/98 | 10/28/98 |
| Mottled Duskywing | Erynnis martialis | 1 | 1 | 5/27/98 | 5/27/98 |
| Mourning Cloak | Nymphalis antiopa | 74 | 37 | 3/30/98 | 12/12/98 |
| Mulberry Wing | Poanes massasoit | 44 | 11 | 6/27/98 | 7/30/98 |
| Mustard White | Pieris napi | 11 | 8 | 4/11/98 | 9/5/98 |
| Northern Broken Dash | Wallengrenia egeremet | 109 | 40 | 6/17/98 | 8/2/98 |
| Northern Cloudywing | Thorybes pylades | 6 | 3 | 6/6/98 | 6/28/98 |
| Northern Pearly Eye | Enodia anthedon | 50 | 20 | 6/18/98 | 7/25/98 |
| Painted Lady | Vanessa carduii | 4 | 3 | 4/23/98 | 8/23/98 |
| Pearl Crescent | Phyciodes tharos | 1391 | 162 | 5/10/98 | 10/17/98 |
| Peck's Skipper | Polites peckius | 128 | 50 | 5/19/98 | 10/19/98 |
| Persius Duskywing | Erynnis persius | 3 | 2 | 5/14/98 | 5/30/98 |
| Pine Elfin | Callophrys niphon | 14 | 3 | 5/5/98 | 5/6/98 |
| Polygonia Species | Polygonia genus (unidentified) | 3 | 2 | 6/27/98 | 7/5/98 |
| Question Mark | Polygonia interrogationis | 18 | 15 | 5/16/98 | 9/13/98 |
| Red Admiral | Vanessa atalanta | 104 | 51 | 4/5/98 | 10/10/98 |
| Red-spotted Purple | Limenitis arthemis astyanax | 79 | 44 | 5/19/98 | 9/13/98 |
| Roadside Skipper | Amblyscirtes vialis | 9 | 6 | 5/14/98 | 7/26/98 |
| Silver-bordered Fritillary | Boloria selene myrina | 19 | 10 | 5/16/98 | 7/26/98 |
| Silver-spotted Skipper | Epargyreus clarus | 378 | 99 | 5/5/98 | 9/19/98 |
| Silvery Blue | Glaucopsych lygdamus | 4 | 2 | 5/23/98 | 5/27/98 |
| Silvery Checkerspot | Chlosyne nycteis | 92 | 9 | 6/18/98 | 8/14/98 |
| Sleepy Duskywing | Erynnis brizo | 53 | 23 | 4/25/98 | 5/31/98 |
| Southern Cloudywing | Thorybes bathyllus | 16 | 11 | 5/23/98 | 8/2/98 |
| Spicebush Swallowtail | Papilio troilus | 67 | 30 | 5/6/98 | 9/20/98 |
| Spring Azure | Celastrina ladon | 154 | 20 | 4/11/98 | 5/19/98 |
| Striped Hairstreak | Satyrium liparops | 14 | 8 | 6/28/98 | 7/25/98 |
| Summer Azure | Celastrina neglecta | 98 | 45 | 6/16/98 | 9/6/98 |
| Tawny Edged Skipper | Polites themistocles | 28 | 22 | 5/21/98 | 8/23/98 |
| Tawny Emperor | Asterocampa clyton | 43 | 12 | 6/21/98 | 7/15/98 |
| Tiger Swallowtail | Papilio glaucus | 131 | 78 | 5/5/98 | 8/15/98 |
| Tiger Swallowtail (Black) | Papilio glaucus | 3 | 3 | 5/21/98 | 8/1/98 |
| Variegated Fritillary | Euptoieta claudia | 5 | 5 | 7/5/98 | 9/12/98 |
| Viceroy | Limenitis archippus | 431 | 125 | 5/21/98 | 10/17/98 |
| White Colias | Colias genus (unidentified) | 235 | 48 | 5/10/98 | 10/26/98 |
| Wild Indigo Duskywing | Erynnis baptisiae | 68 | 22 | 7/5/98 | 9/21/98 |
| Wood Nymph | Cercyonis pegala alope | 375 | 77 | 6/18/98 | 9/19/98 |
Observers: John Farmer, Mike Kielb, Roger Kuhlman, Chris Rickards, John Swales, Roger Wykes
Greater Washtenaw county includes all of Washtenaw county east to Crosswinds Marsh in Western Wayne county, parts of NW Monroe county and Petersburg State Game Area in SW Monroe county