| Species | Latin Name | Numbers | Sightings | First | Last |
|---|---|---|---|---|---|
| Clouded Sulphur | Colias philodice | 4137 | 276 | 4/25/99 | 11/13/99 |
| Cabbage Butterfly | Pieris rapae | 2390 | 376 | 3/31/99 | 11/9/99 |
| Alfalfa Butterfly | Colias eurytheme | 2243 | 202 | 5/2/99 | 11/13/99 |
| Pearl Crescent | Phyciodes tharos | 1865 | 181 | 5/9/99 | 10/15/99 |
| Silver-spotted Skipper | Epargyreus clarus | 820 | 172 | 5/2/99 | 10/16/99 |
| Eastern-tailed Blue | Everes comyntas | 700 | 116 | 5/2/99 | 10/31/99 |
| Viceroy | Limenitis archippus | 615 | 128 | 5/21/99 | 10/9/99 |
| Monarch | Danaus plexippus | 570 | 154 | 5/20/99 | 10/17/99 |
| Great Spangled Fritillary | Speyeria cybele | 550 | 113 | 6/12/99 | 9/22/99 |
| White Colias | Colias genus (unidentified) | 537 | 131 | 5/1/99 | 11/13/99 |
| Little Wood Satyr | Megisto cymela | 482 | 68 | 5/21/99 | 7/25/99 |
| European Skipper | Thymelicus lineola | 481 | 39 | 6/4/99 | 7/20/99 |
| Summer Azure | Celastrina neglecta | 461 | 106 | 6/2/99 | 9/6/99 |
| Black Swallowtail | Papilio polyxenes | 381 | 106 | 4/25/99 | 9/19/99 |
| Tiger Swallowtail | Papilio glaucus | 360 | 155 | 4/26/99 | 9/11/99 |
| Peck's Skipper | Polites peckius | 324 | 90 | 5/21/99 | 10/28/99 |
| Spring Azure | Celastrina ladon | 294 | 39 | 4/8/99 | 5/29/99 |
| Wood Nymph | Cercyonis pegala alope | 264 | 67 | 6/25/99 | 9/2/99 |
| Spicebush Swallowtail | Papilio troilus | 251 | 81 | 5/11/99 | 9/26/99 |
| American Copper | Lycaena phlaeas americana | 232 | 42 | 5/1/99 | 10/25/99 |
| Fiery Skipper | Hylephilia phyleus | 187 | 73 | 6/14/99 | 10/31/99 |
| Buckeye | Junonia coenia | 145 | 58 | 6/9/99 | 11/9/99 |
| Giant Swallowtail | Papilio cresphontes | 135 | 57 | 5/20/99 | 9/18/99 |
| Least Skipper | Ancyloxypha numitor | 135 | 45 | 5/29/99 | 9/18/99 |
| Hobomok's Skipper | Poanes hobomok | 131 | 37 | 5/18/99 | 6/26/99 |
| Tawny Edged Skipper | Polites themistocles | 126 | 47 | 5/27/99 | 9/11/99 |
| Question Mark | Polygonia interrogationis | 115 | 63 | 4/28/99 | 9/25/99 |
| Comma | Polygonia comma | 112 | 63 | 3/27/99 | 11/13/99 |
| Delaware Skipper | Anatrytone logan | 111 | 30 | 6/26/99 | 7/24/99 |
| Wild Indigo Duskywing | Erynnis baptisiae | 108 | 50 | 5/3/99 | 9/26/99 |
| Milbert's Tortoise Shell | Nymphalis milberti | 104 | 31 | 3/20/99 | 10/21/99 |
| Juvenal's Duskywing | Erynnis juvenalis | 90 | 27 | 5/2/99 | 6/25/99 |
| Mourning Cloak | Nymphalis antiopa | 85 | 54 | 3/29/99 | 11/7/99 |
| American Painted Lady | Vanessa virginiensis | 84 | 50 | 4/25/99 | 10/31/99 |
| Baltimore | Euphydryas phaeton | 78 | 20 | 6/12/99 | 7/14/99 |
| Northern Broken Dash | Wallengrenia egeremet | 74 | 30 | 6/19/99 | 9/6/99 |
| Red-spotted Purple | Limenitis arthemis astyanax | 70 | 47 | 5/29/99 | 9/12/99 |
| Silvery Checkerspot | Chlosyne nycteis | 64 | 15 | 5/27/99 | 8/20/99 |
| Red Admiral | Vanessa atalanta | 62 | 50 | 4/24/99 | 11/7/99 |
| Tawny Emperor | Asterocampa clyton | 56 | 15 | 6/19/99 | 7/31/99 |
| Leonard's Skipper | Hesperia leonardus | 52 | 13 | 8/15/99 | 9/19/99 |
| Little Yellow | Eurema lisa | 51 | 15 | 6/11/99 | 10/28/99 |
| Bronze Copper | Lycaena hyllus | 51 | 21 | 5/29/99 | 10/28/99 |
| Dorcas Copper | Lycaena dorcas | 45 | 2 | 7/3/99 | 7/18/99 |
| Black Dash | Euphyes conspicua | 44 | 11 | 6/26/99 | 8/1/99 |
| Mulberry Wing | Poanes massasoit | 44 | 18 | 6/26/99 | 8/1/99 |
| Appalachian Eyed Brown | Satyrodes appalachia | 43 | 15 | 6/20/99 | 8/5/99 |
| Mustard White | Pieris napi | 42 | 18 | 4/26/99 | 9/11/99 |
| Northern Pearly Eye | Enodia anthedon | 42 | 16 | 6/19/99 | 8/15/99 |
| Dun Skipper | Euphyes vestris | 39 | 21 | 6/13/99 | 8/8/99 |
| Common Sootywing | Pholisora catullus | 38 | 21 | 5/22/99 | 9/5/99 |
| Dreamy Duskywing | Erynnis icelus | 34 | 8 | 5/14/99 | 6/20/99 |
| Aphrodite | Speyeria aphrodite | 33 | 5 | 6/20/99 | 9/6/99 |
| Sleepy Duskywing | Erynnis brizo | 25 | 14 | 4/26/99 | 5/15/99 |
| Eyed Brown | Satyrodes eurydice | 25 | 9 | 6/10/99 | 8/1/99 |
| Silver-bordered Fritillary | Boloria selene myrina | 23 | 11 | 5/29/99 | 9/11/99 |
| Crossline Skipper | Polites origenes | 23 | 11 | 6/18/99 | 7/24/99 |
| Meadow Fritillary | Boloria bellona | 22 | 14 | 4/25/99 | 9/5/99 |
| Southern Cloudywing | Thorybes bathyllus | 21 | 11 | 5/28/99 | 7/24/99 |
| Banded Hairstreak | Satyrium calanus | 20 | 13 | 6/19/99 | 7/21/99 |
| Erynnis Species | Erynnis genus (unidentified) | 19 | 10 | 5/2/99 | 7/25/99 |
| Long Dash | Polites mystic | 19 | 8 | 6/4/99 | 6/26/99 |
| Hackberry Butterfly | Asterocampa celtis | 17 | 15 | 6/9/99 | 9/12/99 |
| Harvester | Feniseca tarquinius | 17 | 9 | 7/3/99 | 9/1/99 |
| Acadian Hairstreak | Satyrium acadica | 17 | 12 | 6/21/99 | 7/21/99 |
| Variegated Fritillary | Euptoieta claudia | 16 | 14 | 7/25/99 | 10/30/99 |
| Little Glassywing | Pompeius verna | 15 | 11 | 6/19/99 | 8/3/99 |
| Brown Elfin | Callophrys augustinus | 15 | 3 | 4/14/99 | 5/11/99 |
| Edward's Hairstreak | Satyrium edwardsii | 14 | 3 | 7/3/99 | 7/3/99 |
| Silvery Blue | Glaucopsych lygdamus | 13 | 3 | 5/15/99 | 5/29/99 |
| Horace Duskywing | Erynnis horatius | 11 | 5 | 7/5/99 | 7/25/99 |
| Polygonia Species | Polygonia genus (unidentified) | 10 | 10 | 5/15/99 | 8/29/99 |
| Northern Cloudywing | Thorybes pylades | 10 | 5 | 5/30/99 | 7/4/99 |
| Pine Elfin | Callophrys niphon | 9 | 4 | 4/26/99 | 5/15/99 |
| Coral Hairstreak | Satyrium titus | 8 | 4 | 6/25/99 | 7/4/99 |
| Purplish Copper | Lycaena helloides | 8 | 2 | 9/5/99 | 9/19/99 |
| Hoary Edge | Achalarus lyciades | 8 | 5 | 5/30/99 | 7/3/99 |
| Dion Skipper | Euphyes dion | 7 | 6 | 6/26/99 | 8/1/99 |
| Striped Hairstreak | Satyrium liparops | 7 | 5 | 7/10/99 | 7/18/99 |
| Roadside Skipper | Amblyscirtes vialis | 6 | 5 | 5/11/99 | 8/1/99 |
| Broad-winged Skipper | Poanes viator | 6 | 2 | 7/3/99 | 7/18/99 |
| Harris' Checkerspot | Chlosyne harrisii | 5 | 2 | 6/12/99 | 6/12/99 |
| Persius Duskywing | Erynnis persius | 5 | 3 | 5/2/99 | 5/30/99 |
| Compton's Tortoise Shell | Nymphalis vaualbum | 5 | 4 | 3/31/99 | 8/28/99 |
| American Snout | Libytheana carinenta | 4 | 4 | 6/12/99 | 7/28/99 |
| Pipevine Swallowtail | Battus philenor | 3 | 2 | 7/29/99 | 8/6/99 |
| Dukes Skipper | Euphyes dukesi | 3 | 2 | 7/4/99 | 7/24/99 |
| Gray Hairstreak | Strymon melinus | 3 | 3 | 8/22/99 | 10/11/99 |
| Mottled Duskywing | Erynnis martialis | 2 | 2 | 5/15/99 | 5/15/99 |
| Tiger Swallowtail (Black) | Papilio glaucus | 2 | 2 | 7/24/99 | 8/1/99 |
| Painted Lady | Vanessa carduii | 2 | 2 | 7/10/99 | 7/14/99 |
| Hobomok's Skipper (Pocohantas) | Poanes hobomok | 2 | 2 | 5/30/99 | 6/13/99 |
| Dainty Sulphur | Nathalis iole | 2 | 2 | 10/16/99 | 10/31/99 |
| Hickory Hairstreak | Satyrium caryaevorum | 1 | 1 | 6/26/99 | 6/26/99 |
| Sachem | Atalopedes campestris | 1 | 1 | 9/15/99 | 9/15/99 |
| Cloudless Sulphur | Phoebis sennae | 1 | 1 | 5/21/99 | 5/21/99 |
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