Doug Wechsler / American toad (Bufo americanus) crossing road at night in front of car headlights, Philadelphia, Pennsylvania, USA, March

Michael Hutchinson / Abstract apartment and office buildings, Philadelphia, Pennsylvania, USA

Doug Wechsler / American Toad {Bufo americanus} male calling, his vocal sac vibrations causing ripples in the water, Pennsylvania, USA

Niall Benvie / American alligator (A. mississippiensis) teeth. C. PY, USA. Pennsylvania

Doug Wechsler / Bullfrog male in garden pond {Rana catesbeiana} Pennsylvania, USA.

Tim Fitzharris / Dandelion (Taraxacum officinale) with bee covered with pollen, Pennsylvania

Gerry Ellis / Fall leaf pattern close-up, eastern hardwood forest, Allegheny National Forest, Pennsylvania

Gerry Ellis / Fall leaf pattern close up, eastern hardwood forest, Allegheny National Forest, Pennsylvania

Norbert Wu / Amazon River Dolphin (Inia geoffrensis) melon on forehead used for sonar, Pittsburg Aquarium

John Cancalosi / Timber rattlesnakes emerging from den {Crotalus horridus} Pennsylvania, USA

Doug Wechsler / Bullfrog female by garden pond {Rana catesbeiana} Pennsylvania, USA

Doug Wechsler / Close-up of an Oak leaf changing colour in autumn, Pennsylvania, USA, October.

Doug Wechsler / Wineberry (Rubus phoenicolasius) fruit, Pennsylvania, USA, July.

Doug Wechsler / Grey squirrel (Sciurus carolinensis) outside its drey on tree branch, Pennsylvania, USA, February.

Doug Wechsler / Close-up of a Sugar maple leaf (Acer saccharinum), Pennsylvania, USA, October.

Doug Wechsler / Poison ivy (Toxicodendron radicans) in autumn, Carpenter's Woods, Fairmount Park, Pennsylvania, USA, August.

Doug Wechsler / Chinese mantid (Tenodera aridifolia angustipennis) finishing egg laying on Goldenrod (Solidago), Pennsylvania, USA, September.

Doug Wechsler / Poison ivy (Toxicodendron radicans) vine on tree, Pennsylvania, USA, April.

Doug Wechsler / Poison ivy (Toxicodendron radicans) vine on tree, Pennsylvania, USA, April.

Doug Wechsler / Penn ambersnail (Succinea pennsylvanica) feeding on leaf, Pennsylvania, USA, August.

Doug Wechsler / Peck's skipper butterfly (Polites peckius) roosting on Goldenrod (Solidago) leaf, Pennsylvania, USA, August.

Doug Wechsler / Painted lady butterfly (Vanessa cardui) on Sedum (Sedum spectabile), Pennsylvania, USA, September.

Doug Wechsler / Multicolored asian lady beetle (Harmonia axyridis), Pennsylvania, USA, July.

Doug Wechsler / Multicolored asian ladybird beetle (Harmonia axyridis) pupa metamorphosing to adult, Pennsylvania, USA, July.

Doug Wechsler / Multicolored asian lady beetle (Harmonia axyridis) with aphid (Uroleucon) on Goldenrod, Pennsylvania, USA, August.

Doug Wechsler / Mockernut hickory (Carya tomentosa) nuts, Pennsylvania, USA, September.

Doug Wechsler / Man-made pond in woodland near Wissahickon Creek, Pennsylvania, USA, October 2011.

Doug Wechsler / Locust borer (Megacyllene robiniae) on Goldenrod (Solidago) leaf, Pennsylvania, USA, September.

Doug Wechsler / Large milkweed bug (Oncopeltus fasciatus) nymphs on Common milkweed (Asclepias syriaca) leaf, Pennsylvania, USA, August.

Doug Wechsler / Mating pair of Large milkweed bugs (Oncopeltus fasciatus) on Common milkweed (Asclepias syriaca) leaf, Pennsylvania, USA, July.

Doug Wechsler / Multicolored asian lady beetle (Harmonia axyridis) eggs and newly hatched larva on Common milkweed (Asclepias syriaca), Pennsylvania, USA, July.

Doug Wechsler / Great spangled fritillary butterfly (Speyeria cybele) two on Common milkweed (Asclepias syriaca), Pennsylvania, USA, June.

Doug Wechsler / False potato beetle (Leptinotarsa juncta) larva, Pennsylvania, USA, August.

Doug Wechsler / European paper wasp (Polistes dominula) resting overnight on Goldenrod (Solidago), Pennsylvania, USA, October

Doug Wechsler / Dutchman's breeches (Dicentra cucullaria) Pennsylvania, USA, March.

Doug Wechsler / Dogbane saucrobotys moth (Saucrobotys futilalis) caterpillar on Indian hemp (Apocynum cannabinum) leaf, Pennsylvania, USA, June.

Doug Wechsler / Dogbane beetle (Chrysochus auratus) on Indian hemp (Apocynum cannabinum) leaf, Pennsylvania, USA, June.

Doug Wechsler / Acrobat ants (Crematogaster ashmeadi) nectaring on Common milkweed (Asclepias syriaca), Pennsylvania, USA, July.

Doug Wechsler / Citrus flatid planthopper (Metcalfa pruinosa) on Goldenrod (Solidago), Gwynedd Wildlife Preserve, Pennsylvania, USA, July.

Doug Wechsler / Ambush bug (Phymata americana) attacking Large white butterfly (Pieris rapae), Pennsylvania, USA, June.

Doug Wechsler / Red Trillum (Trillium erecta) on forest floor. Fairmount Park, Philadelphia, Pennsylvania, April.

Doug Wechsler / Red Trillum (Trillium erecta) flower. Fairmount Park, Philadelphia, Pennsylvania, April.

Doug Wechsler / Virginia ctenucha moth (Ctenucha virginica) on milkweed leaf. Philadelphia, Pennsylvania, USA

Doug Wechsler / Milkweed tussock moth / tiger moth caterpillars (Euchaetes egle) first instar and egg mass on common milkweed. Philadelphia, Pennsylvania, USA. July

Doug Wechsler / Large milkweed bug nymphs (Oncopeltus fasciatus) on common milkweed pod (Asclepias syriaca). Philadelphia, Pennsylvania, USA. July

Doug Wechsler / Green Stinkbug nymphs (Acrosternum hilare / Chinavia hilaris) and egg shells on milkweed leaf. Philadelphia, Pennsylvania, USA

Doug Wechsler / Male and female American toads (Bufo americanus) in amplexus on road at night, with car headlights behind. Philadelphia, Pennsylvania, USA

Doug Wechsler / Male and female American toads (Bufo americanus) in amplexus on road at night, with car headlights behind. Philadelphia, Pennsylvania, USA. March

Doug Wechsler / Girl watching male and female American toads (Bufo americanus) in amplexus crossing road at night; Philadelphia, Pennsylvania, USA. March

Doug Wechsler / American toad (Bufo americanus) toadlet with tail: metamorphosing; Philadelphia, Pennsylvania, USA, June

Doug Wechsler / American toad (Bufo americanus) toadlet sitting on leaf; losing tail; Philadelphia, Pennsylvania, USA, May

Doug Wechsler / American toad (Bufo americanus) tadpoles congregating at edge of creek; Fairmount Park, Philadelphia, Pennsylvania, USA, May

Aflo / N-20804 Maize / corn field {Zea mays} with farm buildings in distance, Pennsylvania, USA.

Doug Wechsler / Aphid colony (Uroleucon sp) winged adults and larvae, feeding on Goldenrod (Solidago sp), Pennsylvania, USA

Doug Wechsler / American Toad (Bufo americanus) eggs at day 3, Pennsylvania, USA

Doug Wechsler / Larva of Swamp Milkweed Leaf Beetle (Labidomera clivicollis) feeding on milkweed, Pennsylvania, USA

Doug Wechsler / Aphid colony (Uroleucon sp) adults and larvae on Goldenrod (Solidago sp) Pennsylvania, USA

Doug Wechsler / Stinky squid fungus (Pseudocolus fusiformis) with flies attracted to its odour to disperse spores, Schuylkill Center, Philadelphia, Pennsylvania, USA

Doug Wechsler / Monarch Butterfly caterpillar (Danas plexippus) feeding on Butterflyweed (Ascelepias tuberosa), Pennsylvania, USA

Doug Wechsler / Monarch Butterfly caterpillar (Danas plexippus) feeding on Butterflyweed (Ascelepias tuberosa), Pennsylvania, USA

Doug Wechsler / Milkweed longhorn beetle (Tetraopes tetraophthalmus) on Milkweed (Asclepia tuberosa) Pennsylvania, USA

Doug Wechsler / Long-legged Fly (Condylostylus sp.) on Common milkweed leaf, Pennsylvania, USA

Doug Wechsler / Honey Bee (Apis mellifera) feeding on Butterflyweed flower(Asclepias tuberosa) Pennsylvania, USA

Doug Wechsler / Green Frog (Rana clamitans) tadpole with hind legs developed, mid stage of metamorph, Pennsylvania, USA

Doug Wechsler / Green Frog (Rana clamitans) froglet with tail remaining, metamorphosing, in man-made pond, Farimount Park, Wissahickon Creek, Pennsylvania, USA

Doug Wechsler / Green Frog tadpole (Rana clamitans) mid stage of metamorph, Fairmount Park, Wissahickon, Pennsylvania, USA

Doug Wechsler / Great Spangled fritillary butterfly (Speyeria cybele) feeding on Butterflyweed (Asclepias tuberosa) Philadelphia, Schuylkill Center, Pennsylvania, USA

Doug Wechsler / Fall colors along Wissahickon Creek, Fairmount Park, Pennsylvania, USA

Doug Wechsler / Eastern Grey Squirrel (Sciurus carolinensis) feeding on Sunflower {Helianthus sp}, Philadelphia, Pennsylvania, USA

Doug Wechsler / Eastern Cottontail Rabbit (Sylvilagus floridanus) eating clover, Philadelphia, Pennsylvania, USA

Doug Wechsler / Eastern Cottontail Rabbit (Sylvilagus floridanus) eating clover, Philadelphia, Pennsylvania, USA

Doug Wechsler / Eastern Cottontail Rabbit (Sylvilagus floridanus) Philadelphia, Pennsylvania, USA

Doug Wechsler / American Dog Tick / Wood tick (Dermacentor variabilis) adult on skin full of blood; Schuylkill Center, Pennsylvania, USA

Doug Wechsler / Dog Stinkhorn fungus (Mutinus caninus) Schuylkill Center, Pennsylvania, USA

Doug Wechsler / Bullfrog (Rana catesbeiana) male, in man-made pond, Farimount Park, Wissahickon Creek, Philadelphia, Pennsylvania, USA

Doug Wechsler / Bullfrog (Rana catesbeiana) male, in man-made pond, Farimount Park, Wissahickon Creek, Philadelphia, Pennsylvania, USA

Michael Hutchinson / Grey Squirrel (Sciurus carolinensis), juvenile sitting on branch of colourful crab apple tree (Malus sp) in autumn, Pennsylvania, USA, November

Michael Hutchinson / Grey Squirrel (Sciurus carolinensis) juvenile in colourful Crab apple tree (Malus sp) feeding on red berries, Pennsylvania, USA, November

Michael Hutchinson / American Robin (Turdus migratorius), in colourful crab apple tree (Malus sp), Pennsylvania, USA, November

Michael Hutchinson / American Robin (Turdus migratorius), in crab apple tree (Malus sp), Pennsylvania, USA, November

Michael Hutchinson / Grey Squirrel (Sciurus carolinensis) juvenile in colourful crab apple tree (Malus sp) foraging for red fruits, Pennsylvania, USA

Michael Hutchinson / American Robin (Turdus migratorius), in crab apple tree (Malus sp), Pennsylvania, USA, November

Michael Hutchinson / American Robin (Turdus migratorius), feeding on red fruit of crab apple (Malus sp) Pennsylvania, USA, November

John Cancalosi / Eastern cottontail {Sylvilagus floridanus} Pennsylvania, USA

Doug Wechsler / American Toad {Bufo americanus} male calling, vocal sac inflated, Valley Forge NP, Pennsylvania, USA

Doug Wechsler / Peck's Skipper butterfly {Polites peckius} Pennsylvania, USA

Doug Wechsler / Grey Squirrel {Sciurus carolinensis} carrying leaves up tree trunk to its nest, Pennsylvania, USA

Doug Wechsler / American Toad {Bufo americanus} pair in amplexus, Pennsylvania, USA

Doug Wechsler / American Toad {Bufo americanus} male calling, vocal sac inflated, Pennsylvania, USA

Tim Fitzharris / Kitchen Creek cascades, autumn, Ricketts Glen State Park, Pennsylvania

Tim Fitzharris / Cayuga Falls, Ricketts Glen State Park, Pennsylvania

Tim Fitzharris / Mist over Lackawanna Lake, Lackawanna State Park, Pennsylvania

Niall Benvie / Bird feather on top of slate, Stone quarry, McClure, Pennsylvania, USA

Niall Benvie / Fallen leaves in autumn, in Broad leaved woodland, Pennsylvania, USA

John Cancalosi / Timber Rattlesnakes (Crotalus horridus) Gravid females basking to bring young to term, black and yellow colour morphs, Pennsylvania, USA

Doug Wechsler / Chinese mantid (Tenodera aridifolia) eggs on Goldenrod (Solidago genus), Pennsylvania, USA