Below is a list of nature photography locations in Missouri - please make suggestions in the comments of any additional ones.

Abbreviations:
Busch - Busch Wildlife Area
Cuivre - Cuivre River State Park
Marals - Marals Temps Clair (94 N. from St. Charles to intersection H, follow signs)
Lone Elk - Lone Elk Park (I-44 to Valley Park exit. Follow sign and outer road)
Washington - Washington State Park (12-15 mi. south of Hillsboro on Hwy. 21)
Shaw - Shaw Nature Reserve ("arboretum", I-44 to Gray Summit exit)
St. Francois - St. Francois State Park (Hwy. 67, north of Bonn Terre)
Rockwood - Rockwood Reservation (Hwy. 100 to south on Hwy. 109)
Valley View Glades - Valle View Glades (Hwy. B between Hwy. 30 and 21)

What To Look For	Where To Look	When
Bellwort	Shaw, Busch, Rockwood	April
Bloodroot	Rockwood, Shaw	April
Bluebells	Shaw	April
Box Turtles	Woods	June-August
Buckeyes	Plantain	Sept-October
Bullfrogs	Ponds	July-October
Butterflies	Wildflowers, Butterflyweed	June
Butterfly Weed	Washington, Shaw	June-August
Carrion Beetles	Dead Animals	June-August
Caterpillar Hunter	Anywhere	May
Caterpillars	Anwhere food	April-May
Columbine	Shaw, Shaw's	April-July
Deer	Lone Elk, Busch	Year round
Dragonflies	Cuivre, Marals, Anywhere	June-August
Ducks	Lone Elk, Zoo	October
Dutchman's Breeches	Shaw, Busch, Cuivre	April
Elk	Lone Elk	Year round
Fritillaries	All locations	Last week in May
Geese, Goslings	Busch, Lone Elk	April-June
Glade Flowers	Valley View Glades	May-July
Henbit	Cornfields, Yards	April-May
Hepatica	Washington, Rockwood	April
Hickory Horn Devil	Biological Labs	September
Indian Paintbrush	Shaw, St. Francois	May-June
Leopard Frogs	Cuivre, Ponds	August
Lizards	Woodpiles, Rocks	April-June
Lotus	Busch, Marals, Ponds	August
Milkweed bugs	Milkweed	June-September
Mushrooms	All locations	After rains
Owls	Busch, Large trees	April-May
Pawpaws	Woods	Sept-October
Praying Mantis	Anywhere	Sept-October
Pussy Willows	Busch, Yards	March-April
Question Marks	On Elm leaves	June-August
Red Admirals	On nettles	July-August
Rose Mallow	Marals Temps Clair	July-August
Sheep	Lone Elk	Year round
Snakes	Busch, Marals, Cuivre	April-May
Spiders	Shaw, Busch, Cuivre	Sept-October
Spring Beauties	Woods, anywhere	April
Sulphurs	Meadows, Shaw	July-September
Sunflowers	Roadside	September
Tadpoles	Steams, Ponds	June-August
Toads	Anywhere	June-August
Tomato Hornworms	Tomato Plants	June-August
Turtles	Busch, Marals, Ponds	April-June
Violets	Anywhere	April
Wild Oats	Fencerows	May
Zebra Swallowtails	Busch, Cuivre, Shaw	April-May
Zebra Swallowtails (2nd hatch)	Busch, Cuivre, Woods	July