Dichotomous Keys

Bell Ringer/Start Activity: How do you identify something new to you?

A tool used to identify or classify organisms in the natural world

​It uses a series of binary choices to help ID a species

What is a dichotomous key?

Simply: to narrow choices

There are millions of species, so figuring out if you have a new one takes some work!

​

What are they used for?

• Each choice will list a trait or an instruction/another choice

• If it lists a trait, it will identify the organism

• The choice will ask about another trait

Make a series of binary choices

• Examine the organism you're identifying

• Choose the trait that is most distinguishable

• Look at the first choice on the chart

Start at the beginning

How do you read one?

• You'd start with a picture of an organism

• Follow it down to the end

​

Here's a basic example

This will be the type we'll mostly read

​

Keys can also be word-based

Open Ended

1. • 1a. Deer with a distinctive white underside of the tail. --> End: White-Tailed Deer

   • 1b. Deer without a distinctive white underside of the tail. --> Go to 2

2. • 2a. Deer with large, mule-like ears. --> End: Mule Deer

   • 2b. Deer without large, mule-like ears. --> Go to 3

3. • 3a. Deer with a reddish-brown coat. --> End: Red Deer

   • 3b. Deer with a coat of another color. --> Go to 4

4. • 4a. Deer with a spotted coat pattern. --> End: Sika Deer

   • 4b. Deer without a spotted coat pattern. --> Go to 5

5. • 5a. Deer with distinctive palmate antlers. --> End: Fallow Deer

   • 5b. Deer with antlers of another shape. --> End: Axis Deer

   • ​

   • What type of deer do you have?

Open Ended

1. • 1a. Deer with a distinctive white underside of the tail. --> End: White-Tailed Deer

   • 1b. Deer without a distinctive white underside of the tail. --> Go to 2

2. • 2a. Deer with large, mule-like ears. --> End: Mule Deer

   • 2b. Deer without large, mule-like ears. --> Go to 3

3. • 3a. Deer with a reddish-brown coat. --> End: Red Deer

   • 3b. Deer with a coat of another color. --> Go to 4

4. • 4a. Deer with a spotted coat pattern. --> End: Sika Deer

   • 4b. Deer without a spotted coat pattern. --> Go to 5

5. • 5a. Deer with distinctive palmate antlers. --> End: Fallow Deer

   • 5b. Deer with antlers of another shape. --> End: Axis Deer

   • ​

   • What type of deer do you have?

Open Ended

1. • 1a. Deer with a distinctive white underside of the tail. --> End: White-Tailed Deer

   • 1b. Deer without a distinctive white underside of the tail. --> Go to 2

2. • 2a. Deer with large, mule-like ears. --> End: Mule Deer

   • 2b. Deer without large, mule-like ears. --> Go to 3

3. • 3a. Deer with a reddish-brown coat. --> End: Red Deer

   • 3b. Deer with a coat of another color. --> Go to 4

4. • 4a. Deer with a spotted coat pattern. --> End: Sika Deer

   • 4b. Deer without a spotted coat pattern. --> Go to 5

5. • 5a. Deer with distinctive palmate antlers. --> End: Fallow Deer

   • 5b. Deer with antlers of another shape. --> End: Axis Deer

   • ​

   • What type of deer do you have?

Open Ended

1. • 1a. Deer with a distinctive white underside of the tail. --> End: White-Tailed Deer

   • 1b. Deer without a distinctive white underside of the tail. --> Go to 2

2. • 2a. Deer with large, mule-like ears. --> End: Mule Deer

   • 2b. Deer without large, mule-like ears. --> Go to 3

3. • 3a. Deer with a reddish-brown coat. --> End: Red Deer

   • 3b. Deer with a coat of another color. --> Go to 4

4. • 4a. Deer with a spotted coat pattern. --> End: Sika Deer

   • 4b. Deer without a spotted coat pattern. --> Go to 5

5. • 5a. Deer with distinctive palmate antlers. --> End: Fallow Deer

   • 5b. Deer with antlers of another shape. --> End: Axis Deer

   • ​

   • What type of deer do you have?

Open Ended

1. • 1a. Deer with a distinctive white underside of the tail. --> End: White-Tailed Deer

   • 1b. Deer without a distinctive white underside of the tail. --> Go to 2

2. • 2a. Deer with large, mule-like ears. --> End: Mule Deer

   • 2b. Deer without large, mule-like ears. --> Go to 3

3. • 3a. Deer with a reddish-brown coat. --> End: Red Deer

   • 3b. Deer with a coat of another color. --> Go to 4

4. • 4a. Deer with a spotted coat pattern. --> End: Sika Deer

   • 4b. Deer without a spotted coat pattern. --> Go to 5

5. • 5a. Deer with distinctive palmate antlers. --> End: Fallow Deer

   • 5b. Deer with antlers of another shape. --> End: Axis Deer

   • ​

   • What type of deer do you have?

Open Ended

1. • 1a. Deer with a distinctive white underside of the tail. --> End: White-Tailed Deer

   • 1b. Deer without a distinctive white underside of the tail. --> Go to 2

2. • 2a. Deer with large, mule-like ears. --> End: Mule Deer

   • 2b. Deer without large, mule-like ears. --> Go to 3

3. • 3a. Deer with a reddish-brown coat. --> End: Red Deer

   • 3b. Deer with a coat of another color. --> Go to 4

4. • 4a. Deer with a spotted coat pattern. --> End: Sika Deer

   • 4b. Deer without a spotted coat pattern. --> Go to 5

5. • 5a. Deer with distinctive palmate antlers. --> End: Fallow Deer

   • 5b. Deer with antlers of another shape. --> End: Axis Deer

   • ​

   • What type of deer do you have?

Open Ended

1. 1 Size and Color

A. Small and black or brown - Go to step 2

B. Medium to large size, with colorful markings - Go to step 4

2 Wing Covers (Elytra)

A. Elytra with rows of punctures or ridges - Go to step 3

B. Elytra smooth, without distinct rows of punctures - Go to step 5

3 Antennae Length

A. Antennae shorter than body length - Tenebrio molitor (Mealworm Beetle)

B. Antennae longer than body length - Tribolium castaneum (Red Flour Beetle)

4 Body Shape

A. Oval-shaped body, metallic green or blue - Chrysolina fastuosa (Rosemary Beetle)

B. Elongated body, red with black spots - Harmonia axyridis (Multicolored Asian Lady Beetle)

5 Head Shape

A. Head narrower than thorax - Go to step 6

B. Head wider than thorax - Go to step 7

6 Legs

A. Legs distinctly clubbed or widened at the tips - Calosoma scrutator (Caterpillar Hunter Beetle)

B. Legs not clubbed or widened at the tips - Carabus nemoralis (Bronze Carabid Beetle)

7 Habitat

A. Found near water or damp areas - Dytiscus marginalis (Great Diving Beetle)

B. Found in gardens or wooded areas - Go to step 8

8 Mandibles

A. Mandibles distinctly toothed or serrated - Lucanus cervus (Stag Beetle)

B. Mandibles not distinctly toothed or serrated - Anoplophora glabripennis (Asian Longhorned Beetle)

9 Wing Covers (Elytra)

A. Elytra covering entire abdomen - Go to step 10

B. Elytra leaving part of abdomen exposed - Agriotes lineatus (Wireworm)

10 Wing Covers Texture

A. Elytra with fine, dense punctures - Carabus granulatus (Granulated Carabid Beetle)

B. Elytra with coarse, sparse punctures - Graphoderus liberus (Great Silver Water Beetle)

Open Ended

1. 1 Size and Color

A. Small and black or brown - Go to step 2

B. Medium to large size, with colorful markings - Go to step 4

2 Wing Covers (Elytra)

A. Elytra with rows of punctures or ridges - Go to step 3

B. Elytra smooth, without distinct rows of punctures - Go to step 5

3 Antennae Length

A. Antennae shorter than body length - Tenebrio molitor (Mealworm Beetle)

B. Antennae longer than body length - Tribolium castaneum (Red Flour Beetle)

4 Body Shape

A. Oval-shaped body, metallic green or blue - Chrysolina fastuosa (Rosemary Beetle)

B. Elongated body, red with black spots - Harmonia axyridis (Multicolored Asian Lady Beetle)

5 Head Shape

A. Head narrower than thorax - Go to step 6

B. Head wider than thorax - Go to step 7

6 Legs

A. Legs distinctly clubbed or widened at the tips - Calosoma scrutator (Caterpillar Hunter Beetle)

B. Legs not clubbed or widened at the tips - Carabus nemoralis (Bronze Carabid Beetle)

7 Habitat

A. Found near water or damp areas - Dytiscus marginalis (Great Diving Beetle)

B. Found in gardens or wooded areas - Go to step 8

8 Mandibles

A. Mandibles distinctly toothed or serrated - Lucanus cervus (Stag Beetle)

B. Mandibles not distinctly toothed or serrated - Anoplophora glabripennis (Asian Longhorned Beetle)

9 Wing Covers (Elytra)

A. Elytra covering entire abdomen - Go to step 10

B. Elytra leaving part of abdomen exposed - Agriotes lineatus (Wireworm)

10 Wing Covers Texture

A. Elytra with fine, dense punctures - Carabus granulatus (Granulated Carabid Beetle)

B. Elytra with coarse, sparse punctures - Graphoderus liberus (Great Silver Water Beetle)

Open Ended

1. 1 Size and Color

A. Small and black or brown - Go to step 2

B. Medium to large size, with colorful markings - Go to step 4

2 Wing Covers (Elytra)

A. Elytra with rows of punctures or ridges - Go to step 3

B. Elytra smooth, without distinct rows of punctures - Go to step 5

3 Antennae Length

A. Antennae shorter than body length - Tenebrio molitor (Mealworm Beetle)

B. Antennae longer than body length - Tribolium castaneum (Red Flour Beetle)

4 Body Shape

A. Oval-shaped body, metallic green or blue - Chrysolina fastuosa (Rosemary Beetle)

B. Elongated body, red with black spots - Harmonia axyridis (Multicolored Asian Lady Beetle)

5 Head Shape

A. Head narrower than thorax - Go to step 6

B. Head wider than thorax - Go to step 7

6 Legs

A. Legs distinctly clubbed or widened at the tips - Calosoma scrutator (Caterpillar Hunter Beetle)

B. Legs not clubbed or widened at the tips - Carabus nemoralis (Bronze Carabid Beetle)

7 Habitat

A. Found near water or damp areas - Dytiscus marginalis (Great Diving Beetle)

B. Found in gardens or wooded areas - Go to step 8

8 Mandibles

A. Mandibles distinctly toothed or serrated - Lucanus cervus (Stag Beetle)

B. Mandibles not distinctly toothed or serrated - Anoplophora glabripennis (Asian Longhorned Beetle)

9 Wing Covers (Elytra)

A. Elytra covering entire abdomen - Go to step 10

B. Elytra leaving part of abdomen exposed - Agriotes lineatus (Wireworm)

10 Wing Covers Texture

A. Elytra with fine, dense punctures - Carabus granulatus (Granulated Carabid Beetle)

B. Elytra with coarse, sparse punctures - Graphoderus liberus (Great Silver Water Beetle)

Open Ended

1. 1 Size and Color

A. Small and black or brown - Go to step 2

B. Medium to large size, with colorful markings - Go to step 4

2 Wing Covers (Elytra)

A. Elytra with rows of punctures or ridges - Go to step 3

B. Elytra smooth, without distinct rows of punctures - Go to step 5

3 Antennae Length

A. Antennae shorter than body length - Tenebrio molitor (Mealworm Beetle)

B. Antennae longer than body length - Tribolium castaneum (Red Flour Beetle)

4 Body Shape

A. Oval-shaped body, metallic green or blue - Chrysolina fastuosa (Rosemary Beetle)

B. Elongated body, red with black spots - Harmonia axyridis (Multicolored Asian Lady Beetle)

5 Head Shape

A. Head narrower than thorax - Go to step 6

B. Head wider than thorax - Go to step 7

6 Legs

A. Legs distinctly clubbed or widened at the tips - Calosoma scrutator (Caterpillar Hunter Beetle)

B. Legs not clubbed or widened at the tips - Carabus nemoralis (Bronze Carabid Beetle)

7 Habitat

A. Found near water or damp areas - Dytiscus marginalis (Great Diving Beetle)

B. Found in gardens or wooded areas - Go to step 8

8 Mandibles

A. Mandibles distinctly toothed or serrated - Lucanus cervus (Stag Beetle)

B. Mandibles not distinctly toothed or serrated - Anoplophora glabripennis (Asian Longhorned Beetle)

9 Wing Covers (Elytra)

A. Elytra covering entire abdomen - Go to step 10

B. Elytra leaving part of abdomen exposed - Agriotes lineatus (Wireworm)

10 Wing Covers Texture

A. Elytra with fine, dense punctures - Carabus granulatus (Granulated Carabid Beetle)

B. Elytra with coarse, sparse punctures - Graphoderus liberus (Great Silver Water Beetle)