Dichotomous Keys - Text Format.

Arthropods - Key A: Arthropods with Six Legs, with Well-Developed Wings.

Tips: Only adult arthropods are included, and certain uncommon orders are not included. To use a key, read both descriptions in a couplet (for instance, 1a and 1b). Decide which sounds most like your critter, and move to the next couplet indicated. Should you reach a dead-end, use the numbers in parentheses to backtrack until you reach a couplet that you felt unsure about, and try following the other path. Some orders are found more than once in the keys, because the arthropods occur in different forms.

STEPFROMCHARACTERSORDER / CLASS

1aOne pair of wings. . . . . . . . . . go to 2

1bTwo pairs of wings. . . . . . . . . . go to 3

2a1aHind wings reduced to tiny knobs (halteres), tip of abdomen without 2-3 thread-like tailsDIPTERA(Flies)

2b1aHind wings not reduced to tiny knobs, tip of abdomen with 2-3 thread-like tails (caudal filaments)EPHEMEROPTERA(Mayflies)

3a1bFront and hind wings have similar texture. . . . . . . . . . go to 4

3b1bFront wings a rigid or leathery covering for clear hind wings. . . . . . . . . . go to 14

4a3aWings covered with powdery scales, mouthparts usually a coiled tube (proboscis) for suckingLEPIDOPTERA(Moths / Butterflies)

4b3aWings not covered with powdery scales, mouthparts not a coiled tube. . . . . . . . . . go to 5

5a4bWings slope downwards (rooflike) from the center at rest. . . . . . . . . go to 6

5b4bWings not held rooflike at rest. . . . . . . . . . go to 9

6a5aWings covered with hairTRICHOPTERA(Caddisflies)

6b5aHairless wings. . . . . . . . . . go to 7

7a6bSucking mouthparts in the form of a rigid beak, often short and bristley antennae, body may look like a thornHOMOPTERA(Hoppers)

7b6bMouthparts not in the form of a rigid beak, antennae not short and bristley, body never looks like a thorn. . . . . . . . . . go to 8

8a7bWings with many cross veinsNEUROPTERA(Lacewings)

8b7bWings without many cross veinsPSOCOPTERA(Bark lice)

9a5bFront and hind wings similar in size and shape. . . . . . . . . . . go to 10

9b5bFront and hind wings not similar in size and shape. . . . . . . . . .go to 12

10a9aAntennae always short and bristleyODONATA (Dragonflies & Damselflies)

10b9aAntennae never short and bristley. . . . . . . . . . go to 11

11a10bWings held flat over abdomen when at rest, last abdominal segment not enlarged, usually found in coloniesISOPTERA(Termites)

11b10bWings not held flat over abdomen when at rest, males with the last abdominal segment enlarged like a scorpion's stinger and held over the body, not found in coloniesMECOPTERA(Scorpionflies)

12a9bBody very soft, without a narrow "waist". . . . . . . . . . go to 13

12b9bBody not exceptionally soft, often with a narrow "waist"HYMENOPTERA(Bees & Wasps)

13a12aHind wings wider than front wings, folded underneath like a fanPLECOPTERA(Stoneflies)

13b12aHind wings much smaller than front wings, not folded underneath like a fanEPHEMEROPTERA(Mayflies)

14a3bSucking mouthparts in the form of a rigid beak, front wings with clear tips (hemelytra), overlapping at rest, revealing a triangular panel on the back (scutellum)HETEROPTERA(True Bugs)

14b3bChewing mouthparts, front wings without clear tips. . . . . . . . . . go to 15

15a14bRigid front wings (elytra) meet in a straight line down the middle of the backCOLEOPTERA(Beetles)

15b14bFront wings not as above. . . . . . . . . . go to 16

16a15bHead visible from above. . . . . . . . . . go to 17

16b15bHead hidden from above by a hoodlike structure (pronotum)BLATTARIA(Cockroaches)

17a16aFront legs strong with prominent spines for grasping prey, hind legs long and slenderMANTODEA(Mantids)

17b16aFront legs without spines or with weak spines, the femora of the hind legs are enlarged for jumpingORTHOPTERA(Grasshoppers & Crickets)

Dichotomous Keys - Text Format.

Arthropods - Key B: Arthropods with Six Legs, with Tiny or Missing Wings.

Tips: Only adult arthropods are included, and certain uncommon orders are not included. To use a key, read both descriptions in a couplet (for instance, 1a and 1b). Decide which sounds most like your critter, and move to the next couplet indicated. Should you reach a dead-end, use the numbers in parentheses to backtrack until you reach a couplet that you felt unsure about, and try following the other path. Some orders are found more than once in the keys, because the arthropods occur in different forms.

STEPFROMCHARACTERSORDER / CLASS

1aDoes not resemble a twig. . . . . . . . . . go to 2

1bSlow-moving, resembles a twigPHASMIDA(Walking sticks)

2a1aBody very soft. . . . . . . . . . go to 3

2b1aBody not exceptionally soft. . . . . . . . . . go to 8

3a2aMouthparts hidden within head, usually with a springlike structure (furcula) on the underside of the abdomen used for jumpingCOLLEMBOLA(Springtails)

3b2aExternal mouthparts, without a springlike structure on the underside of the abdomen. . . . . . . . . . go to 4

4a3bVisible projections at the tip of the abdomen. . . . . . . . . . go to 5

4b3bNo visible projections at the tip of the abdomen. . . . . . . . . . go to 6

5a4aLong flattened body, tip of abdomen with 2 - 3 long tails (cerci, and if a third tail is present, a median caudal filament)THYSANURA(Silverfish)

5b4aSmall pear-shaped body, tip of abdomen has two short projections (cornicles), some individuals have wingsHOMOPTERA(Aphids)

6a4bUsually found in colonies with many individuals (soldier caste), some of which have very large heads and mandibles (soldier caste) or mouthparts that look like a tube (nasuti caste)ISOPTERA(Termites)

6b4bTiny insects that may be found in groups of many individuals, but they all have the same kind of mouthparts . . . . . . . . . . go to 7

7a6bChewing mouthparts, relatively long antennae, when individuals have wings the wings never have fringes of hairPSOCOPTERA(Bark lice)

7b6bSucking mouthparts, fairly short antennae, adults may actually have barely visible wings with fringes of hairTHYSANOPTERA(Thrips)

8a2bBody with a narrow "waist," antennae usually have a bend in the middleHYMENOPTERA (Ants & Wingless wasps)

8b2bBody without a narrow "waist", antennae don't usually have a bend in the middle. . . . . . . . . . go to 9

9a8bTiny jumping parasites found on mammals or birds, where they suck bloodSIPHONAPTERA(Fleas)

9b8bNot found on mammals or birds, chewing mouthparts. . . . . . . . . . go to 10

10a9bProminent "pincers" at the tip of the abdomen (cerci)DERMAPTERA(Earwigs)

10b9bWithout "pincers" at the tip of the abdomenCOLEOPTERA(Beetles)

Dichotomous Keys - Text Format

Arthropods - Key C: Arthropods with More Than Six Legs.

Tips: Only adult arthropods are included, and certain uncommon orders are not included. To use a key, read both descriptions in a couplet (for instance, 1a and 1b). Decide which sounds most like your critter, and move to the next couplet indicated. Should you reach a dead-end, use the numbers in parentheses to backtrack until you reach a couplet that you felt unsure about, and try following the other path. Some orders are found more than once in the keys, because the arthropods occur in different forms.

STEPFROMFEATURESORDER / CLASS

1aFour pairs of legs. . . . . . . . . . go to 2

1bMore than four pairs of legs. . . . . . . . . . go to 6

2a1aAbdomen with distinct segments. . . . . . . . . . go to 3

2b1aAbdomen without distinct segments. . . . . . . . . . go to 5

3a2aConspicuous "pincers" (pedipalps) in front of shorter legs. . . . . . . . . . go to 4

3b2aWithout "pincers," long and slender legsOPILIONES(Daddy-Longlegs)

4a3aFairly large, the abdomen ends in a stingerSCORPIONES(Scorpions)

4b3aSmall, the abdomen does not end in a stingerPSEUDOSCORPIONES(Pseudoscorpions)

5a2bBody clearly divided into two main parts (cephalothorax and abdomen)ARANEAE(Spiders)

5b2bOval-shaped body not divided into two main partsACARI(Mites & Ticks)

6a1bSeven pairs of tiny legs, some roll up into ballsISOPODA(Pillbugs, sowbugs)

6b1bMore than seven pairs of legs, they don't roll up into balls. . . . . . . . . . go to 7

7a6bTiny bodies, 10 - 12 pairs of legsSYMPHYLA(Symphylans)

7b6bBodies often fairly large, with > 15 pairs of legs. . . . . . . . . . go to 8

8a7bFlattened bodies, with one pair of legs attached to each body segmentCHILOPODA(Centipedes)

8b7bBodies usually tubelike, with two pairs of legs attached to each body segmentDIPLOPODA(Millipedes)

Dichotomous Keys - Text Format

Keys To Common Families Of Heteroptera (True Bugs)

SUBKEY A: Common Families Of Terrestrial Heteroptera (Terrestrial Bugs)

No.From No.DescriptionGotoName

1aA short beak tucks into a groove between the front legsReduviidae(Assassin and Ambush Bugs)

1bThe beak doesn't tuck into a groove between the front legs2

2a1bThe front wings have a lacy pattern; the pronotum is pointed at the baseTingidae(Lace Bugs)

2b1bThe front wings don't have a lacy pattern; the pronotum is not pointed at the base3

3a2bThe body is very slender with threadlike legs and antennaeBerytidae(Stilt Bugs)

3b2bThe body and legs are somewhat broader4

4a3bThe large scutellum extends at least halfway to the end of the abdomen; the antennae have five segments5

4b3bThe scutellum extends less than halfway to the end of the abdomen; the antennae have four segments8

5a4aThe scutellum is usually triangular (if rounded, it does not reach the end of the abdomen)6

5b4aThe scutellum is rounded at the bottom and almost reaches the end of the abdomen7

6a5aThe tibiae have strong spinesCydnidae(Burrower Bugs)

6b5aThe tibiae don't have strong spinesPentatomidae(Stink Bugs)

7a5bThe body is shiny black and < 8 mm longThyreocoridae(Negro Bugs)

7b5bThe body is usually brownish and > 8 mm longScutelleridae(Shield-backed Bugs)

8a4bThe body is extremely flat and rather broad9

8b4bThe body is not extremely flat and broad10

9a8aWings are present but they do not cover the entire abdomenAradidae(Flat Bugs)

9b8aWings are missingCimicidae(Bed Bugs)

10a8bThe tiny bodies are black and white; the clear parts of the front wings lack defined veinsAnthocoridae(Minute Pirate Bugs)

10b8bThe clear parts of the front wings have some well-defined veins11

11a10bThe clear parts of the front wings have five or fewer longitudinal veins12

11b10bThe clear parts of the front wings have more than five longitudinal veins13

12a11aThe clear parts of the front wings have one or two closed cells; ocelli are missingMiridae(Plant Bugs)

12b11aThe clear parts of the front wings do not have closed cells; ocelli are presentLygaeidae(Seed Bugs)

13a11bOcelli are present14

13b11bOcelli are missing16

14a13aThe body is often less than 10 mm long and pale in color (sometimes up to 14 mm long and red and black); and does not produce an odorRhopalidae(Scentless Plant Bugs)

14b13aThe body is usually > 10 mm long, dark in color, and produces a strong odor15

15a14bThe head is narrower than the pronotumCoreidae(Leaf-footed Bugs)

15b14bThe head is about as wide as the pronotumAlydidae(Broad-headed Bugs)

16a13bThe body is usually dark in color, slender, and less than 11 mm longNabidae(Damsel Bugs)

16b13bThe body is often brightly colored, somewhat broad, and greater than11 mm long17

17a16bThe upper surface of the pronotum is convex and its sides do not look 'pinched' flat, the underside of the last abdominal segment of the female has a longitudinal slitLargidae(Largid Bugs)

17b16bThe upper surface of the pronotum is not convex and its sides look 'pinched' flat, the underside of the last abdominal segment of the female does not have a longitudinal slitPyrrhocoridae(Red Bugs, Cotton Stainers)

SUBKEY B: Common Families Of Aquatic and Semiaquatic Heteroptera (Water and Shore Bugs)

No.From No.DescriptionGo ToName

1aThe antennae are shorter than the head and usually concealed2

1bThe antennae are at least as long as the head and usually visible8

2a1aThe body resembles a small toad; found at the edges of ponds or streamsGelastocoridae(Toad Bugs)

2b1aThe body doesn't resemble a toad3

3a2bThe long cerci form a breathing tubeNepidae(Water Scorpions)

3b2bThe cerci are short or missing4

4a3bThe front femora are enlarged; the body is flat and rather broad5

4b3bThe front femora are not enlarged; The body is not flat and broad6

5a4aThe body is less than 16 mm long and ovalNaucoridae(Creeping Water Bugs)

5b4aThe body is at least 20 mm long and somewhat elongatedBelostomatidae(Giant Water Bugs)

6a4bThe tarsi of the front legs look like "scoops"Corixidae(Water Boatman)

6b4bThe tarsi of the front legs do not look like "scoops"7

7a6bThe body is at least 5 mm longNotonectidae(Backswimmers)

7b6bThe tiny body is less than 3.5 mm longPleidae(Pygmy Backswimmers)

8a1bThe long, narrow body is usually at least 5 mm long; the legs are long and very slender9

8b1bThe broader body is usually less than 5 mm long; the legs are not extremely long and slender10

9a8aThe front legs are much shorter than the mid and hind legs; the head is shortGerridae(Water Striders)

9b8aThe front legs are about as long as the mid and hind legs; the head is about as long as the front femoraHydrometridae(Water Measurers)

10a8bThe body is usually greenish or yellowishMesoveliidae(Water Treaders)

10b8bThe body is usually dark or black and white11

11a10bThe clear parts of the front wings have four or five closed cellsSaldidae(Shore Bugs)

11b10bWhen wings are present, the clear parts of the front wings do not have four or five closed cells12

12a11bThe body looks like that of a miniature water strider and is not covered with velvety hairsVeliidae(Riffle Bugs)

12b11bThe body does not look like that of a miniature water strider and is covered with velvety hairsHebriidae(Velvet Water Bugs)

Dichotomous Keys - Text Format

Keys To Common Families Of Neuroptera (Lacewings, Antlions, etc.)

No.FromDescriptionGotoName

1aThe front and hind wings are both narrow where they attach to the body 3

1bThe hind wings have a conspicuous "heel" where they attach to the body

2

2a1bThe body is usually at least 25 mm long; ocelli are presentCorydalidae(Dobsonflies, Fishflies)

2b1bThe body is usually < 25 mm long; ocelli are missingSialidae(Alderflies)

3a1aThe prothorax is exceptionally long (like a mantid)4

3b1aThe prothorax is not exceptionally long6

4a3aThe front legs are enlarged and attached to the prothorax near the headMantispidae(Mantidflies)

4b3aThe front legs are not enlarged and are attached to the prothorax near the middle legs (Snakeflies)5

5a4bOcelli are presentRaphidiidae(Raphidid Snakeflies)

5b4bOcelli are missingInocelliidae(Inocellid Snakeflies)

6a3bThe antennae are clubbed7

6b3bThe antennae are filiform, moniliform, or pectinate8

7a6aThe antennae are much shorter than the bodyMyrmeleontidae(Antlions)

7b6bThe antennae are about as long as the bodyAscalaphidae(Owlflies)

8a6bMany cross veins fork before reaching the front edge of the wing (spread the wings to check which is the front edge

Hemerobiidae(Brown Lacewings)

8b6bFew cross veins fork before reaching the front edge of the wing

9

9a8bThe body is usually greenish in color; these are found on plantsChrysopidae(Green Lacewings)

9b8bThe body is usually brownish in color; these are found near ponds or streamsSisyridae(Spongillaflies)

Dichotomous Keys - Text Format

Key to common families of Orthoptera (Grasshoppers & Crickets).

No.FromDescriptionGotoName

1aThe front femora are almost as long and thick as the hind femora2

1bThe hind femora are much longer and thicker than the front femora3

2a1aThe front tibiae are modified into scoops for diggingGryllotalpidae(Mole Crickets)

2b1aThe front tibiae are enlarged, but not modified into scoopsGryllacridadae(Jerusalem Crickets)

3a1bThe pronotum extends to cover the abdomenTetrigidae(Pygmy Grasshoppers)

3b1bThe pronotum does not cover the abdomen4

4a3bThe body is 4-10 mm long; the end of the abdomen has two pairs of projectionsTridactylidae(Pygmy Mole Crickets)

4b3bThe body is usually >10 mm long, the end of the abdomen has one pair of projections (cerci)5

5a4bThe antennae are short (usually less than half as long as the body); auditory organs, when present, are on he sides of the first abdominal segment6

5b4bThe antennae are long (usually at least as long as the body); auditory organs, when present, are on the front tibiae7

6a5aThe antennae are shorter than the front femora; wings are missingEumasticidae(Monkey Grasshoppers)

6b5aThe antennae are longer than the front femora; wings are presentAcrididae(Short-horned Grasshoppers)

7a5bThe wings are missing; the body is humpbackedGryllacridadae(Cave Crickets)

7b5bThe wings are present but sometimes small; the body is not usually humpbacked8

8a7aThe ovipositor is shaped like a needle; the body is often brownGryllidae(Crickets)

8b7bThe ovipositor is flattened like a sword; the body is usually greenTettigoniidae(Long-horned Grasshoppers, Katydids)

22