The Evolution of Insects 1

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The Evolution of Insects -1
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Insect Evolution

• The Apterygota
• The Paleoptera
• The Neoptera with Incomplete Metamorphosis

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Hypothetical Stages in the Evolution of the
Insect Form
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Major Events in the Evolution of Insects
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Subclass Apterygota 6 legs present primitively
wingless Insects
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Order Collembola - springtails
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Order Thysanura - silverfish
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Major Events in the Evolution of Insects
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Subclass Pterygota Insects with wings OR those
that have secondarily lost them.
Paleoptera Insects That Have Wings but Cannot
Fold Them
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What are the theories proposed to explain the
origin of wings?

• Terrestrial origin - paranotal expansion theory
  wings developed first as slight lateral
  extensions of the dorsal side of the thorax. At
  first, these did not articulate and were used as
  gliding devices. Fossil evidence (Devonian)
  supports 3 pair of these rather than 2.
• Aquatic origin wings evolved from platelike
  gills along the side of the thorax of the aquatic
  stage and that were retained into the adult
  stage.

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Did wings originate from tracheal gills in
aquatic insects such as mayfly ancestors?
Mayfly nymphs
Tracheal gills
Note that mayflies molt once after reaching the
adult stage.
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Order Odonata dragonflies and damselflies
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Damsel Fly
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Study Questions

• In what ways are dragonflies different from
  damselflies?
• What kinds of aquatic habitats are the Odonata
  found in?
• What niche is occupied by the juveniles?

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Order Ephemeroptera - mayflies
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Study Questions

• What niches are occupied by mayfly nymphs?
• At what times of the year do mayflies hatch.
• What kinds of food chains are mayflies a part of?

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Insects with Incomplete Metamorphosis Chewing
Mouthparts Nymphs Having Ocelli All groups now
can fold their wings
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American Cockroach adult I need some cheese
with this!
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Study Questions

• What is the economic and public health
  significance of cockroaches?
• Where are they located in homes?
• What do they feed on?

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Mantid I can be a real tough dude
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A Katydid
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Order Isoptera worker termite
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Extensive Termite Damage
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Insects With Incomplete Metamorphosis Piercing-Su
cking Mouthparts Nymphs without ocelli Chewing
mouthparts may be secondarily derived
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Order Hemiptera stink bugs
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Order Hemiptera Family Reduviidae assassin
bugs
This species is known as the wheel bug
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Assassin bug feeding on 2nd. Instar caterpillar
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Study Questions

• How are members of this Order distinguished from
  the beetles, Order Coleoptera?

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Order Homoptera cicada emergence
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Study Questions

• Look very closely at the previous slide
  illustrating cicada emergence. What have you
  learned about in this class so far that is
  clearly observable on this slide?

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Treehoppers lined up on a branch Order Homoptera
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Study Questions

• Give some common names of at least 5 groups of
  insects that are related to treehoppers (Order
  Homoptera)

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Pubic Louse actual size!!
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Study Questions

• Where do pubic lice live?
• In what way(s) are they of importance to humans?
• Are they considered to be important disease
  vectors?