dichotomous keys based on dichotomies, you must choose one of two options by repeating this step,...

DICHOTOMOUS KEYS

• Based on dichotomies, you must choose one of two options

• By repeating this step, you can narrow down to more and more specific classifications

• Answers often involve whether a diagnostic trait is present

• Example: Does this insect have wings?

Does it have cerci (tails?)

ODONATA

• Does it have a stout body and hold its wings flat at rest?

• Is Body Longer than Wingspan?

• Do its eyes touch at top of head?

Odonata

AnisopteraDragonfly

GomphidaeClubtails

AeshnidaeDarners

LibellulidaeSkimmers

ZygopteraDamselfly

LestidaeSpreadwings

CoenagrionidaeNarrow Winged

HOW THE KEY WOULD LOOK

1. It has wings 4

It doesn’t have wings 2

2. It has six legs 3

It doesn’t have six legs it’s not an insect

3. Its ancestors have wings 4

It never had wings apterygota

4. It only lives for a day ephemeroptera

It lives for many days 5

5. It has bulging eyes Zygoptera

Its eyes do not bulge Anisoptera

FRUIT KEY EXERCISE

ORDER BLATTODEA: ROACHES

• What makes a cockroach?

• Cockroaches Are not the same as beetles!!!

• Distinguished by ‘hood’. Extension of pronotum covering head.

• ‘Dorso-ventrally’ flattened…

• Usually brown drab color

• Cylindrical egg sack, attached to female’s posterior

• Have functional wings, but rarely fly

• Two short cerci

• Long thin antennae

EW?• Only a few are pests• Most cockroachs feed on decaying

wood, fruit, and other plant matter• Cockroaches are very important

decomposers• Take plant matter and make it into

food for other critters

• However, some cockroaches (American roach, Oriental roach especially) are icky

• Tend to invade homes• Do NOT spread disease…• But eat and spoil foodstuffs• Also, these species smell bad