Myriapods, Hexapods
1
• Subphylum Hexapoda + Subphylum Myriapoda
– (primarily) terrestrial mandibulates
• Paired mouthparts- chewing/grinding/tearing
Homopteran
movie
Orthopteran
2
• Subphylum Hexapoda + Subphylum Myriapoda
– Uniramous (unbranched) appendages
Biramous
appendage
3
• Subphylum Hexapoda + Subphylum Myriapoda
– One pair of antennae
4
• Subphylum Hexapoda + Subphylum Myriapoda
– Use tracheae to carry respiratory gasses
• Chitin-lined invaginations of epithelium
• Open to the outside via spiracles
5
• Subphylum Hexapoda + Subphylum Myriapoda
– Excretion by Malpighian tubules
• Almost all insects, some myriapods, some
spiders
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– Excretion by Malpighian tubules (cont’d)
• Blind-ended tubules bathed in hemolymph
– Remove nitrogenous waste (e.g. uric acid), amino
acids, sugars
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– Excretion by Malpighian tubules (cont’d)
• Minerals, water resorbed at bottom of tubule
and by rectal glands of hindgut
– waste passed out
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Myriapods
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Subphylum Myriapoda
• “many footed”
• Class Chilopoda
• Class Diplopoda
Diplopoda
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Class Chilopoda
• centipedes
• Serial segmented, flattened body
• each segment has a pair of jointed appendages
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Class Chilopoda (cont’d)
•
Active predators
– kill prey with poison claws and fangs (modified
legs on first segment)
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Class Diplopoda
• Millipedes
• Serially segmented, rounded body
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Class Diplopoda
• 2 smaller pairs of legs per segment
• Slow moving; feed on decaying plants movie
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Subphylum Hexapoda
• Includes Class Insecta
– Beetles, grasshoppers, butterflies, flies, bees…
– Movie
– movie
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Class Insecta
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Most Abundant and Diverse
Animal Class
• 1,000,000+ species
identified
– May as many as
10,000,000
• More than all other
animals combined
17
Distribution of Insects
• Air
• land
• In the soil
• Parasites
– Plants
– Animals
• Freshwater
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Reasons for insect success
• Small size
• Reproductive potential
• Co-evolution with
plants
• Evolution of flight
• Metamorphosis
19
Characteristics of Insects
• Three body regions
– Head
– Thorax
– Abdomen
• Three pair of legs
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Characteristics (cont)
• wings
– Absent in some
• Pair of compound eyes
• Spiracles for
respiration
21
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
External Structure of a Generalized Insect
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Internal Structure of a Generalized Insect
Fig. 15.8
15-6
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External structure of insects
Head
•
one pair of antennae
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External structure of insects
Head
• pair of compound eyes (detect movement)
• several sets of simple eyes= ocelli (probably
detect changes in light intensity)
Mosquito compound eye
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External structure of insects (cont’d)
Head
• Antennae can be
highly variable
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Mosquito antennae
External structure of insects (cont’d)
• Mouthparts are highly modified depending
on the type of insect
– for piercing and sucking
(ie. mosquitos)
– movie
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External structure of insects (cont’d)
• Mouthparts are highly modified depending
on the type of insect
– for chewing
(ie. grasshoppers)
– movie
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External structure of insects (cont’d)
• Mouthparts are highly modified depending
on the type of insect
– for siphoning (ie. butterflies)
– movie
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External structure of insects (cont’d)
• Mouthparts are highly modified depending
on the type of insect
– for sponging (ie. flies)
Movie
damselfly eating moth
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External structure of insects (cont’d)
Thorax
• consists of three regions:
– Prothorax (anterior-most segment)
– Mesothorax
– Metathorax
• One pair of legs
attaches along
ventral
margin of each
thoracic region
31
External structure of insects (cont’d)
• Insects may have 1 pair, 2
pair, or no wings
• Insects are the only
invertebrates that can fly
movie
Drosophila melanogaster
Archaeognatha
(bristletail)
32
• Wings of insects= modified exoskeleton
• 1st pair is often tough and leathery
(protection)
– fold over the inner pair
.
33
• Attach to mesothorax and metathorax
• Have thickened, hollow veins for increased
strength
.
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Abdomen
– does not have appendages
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Abdomen
– terminal portions harbor the reproductive
structures
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Insects undergo
metamorphosis
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Metamorphosis
• Change in form from
one developmental
stage to another
• Immature and adult
body forms
Yellow bear caterpillar
• May not compete
• May be incomplete or
complete
Monarch butterfly chrysalis
38
Apollo butterfly
Incomplete Metamorphosis
• Early developmental
stages very similar to
adults
• only the wings and
reproductive structures
gradually develop
cockroach
39
Incomplete metamorphosis (cont’d)
• The immature stages = nymphs
– egg---> nymphs ----> adult
cockroach
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Complete metamorphosis
• Each stage is
structurally and
functionally very
different
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Complete metamorphosis (cont’d)
•
The egg develops into
an immature larva;
eats voraciously
• movie
42
Complete metamorphosis (cont’d)
• Followed by a
transitional stage pupa, contained within
cocoon
43
Complete metamorphosis (cont’d)
• Metamorphosis occurs
within the pupal
exoskeleton, yielding a
sexually mature adult
movie
44
Beneficial Insects
• Honey bee
– Honey
– Pollinates crops
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Beneficial Insects
• Silkworm moth
• Lava produces silk
46
Beneficial Insects
• Breakdown dung
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Beneficial Insects
• Blow fly
• Decompose dead bodies
48
Beneficial Insects
• Lady bug
• Eats harmful insects
• Saved California citrus
in ’20s
49
Beneficial Insects
• Some wasps
• Kill harmful insects
– Parasitoid
• Larvae live in body of
host, eventually
killing it
• movie
50
Fruit Fly
• Drosophila
• Genetics research
51
• Some genes are
highly conserved
among organisms
• NCBI
52
Harmful Insects
• Boll weevil
• Destroys cotton
53
Harmful Insects
• Tent caterpillar
• Pest of many trees and
shrubs
54
Harmful Insects
• Mosquitos
• Vector
–
–
–
–
–
–
Malaria
Yellow fever
Encephalitis
West Nile virus
Movie
Web-linked movie,
better
55
Harmful Insects
• Flea
• Vector for
– Plague
Xenopsylla Cheopis
56
Black Death
• Bubonic plague
• 1357-1350 killed
25,000,000 in Europe
• 1900’s killed
20,000,000 in India
58
Plague
Survivor
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60
Alexandre Yersin
• Discovered bacterium
• Yersinia pestis
• Treated with
antibiotics
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