Download The Hexapods and Myriapods: Terrestrial Triumphs

The Hexapods and Myriapods:
Terrestrial Triumphs
Chapter 15
Zoology
The Insects
• 750,000 + species insects
described, but may be 30 million
species undescribed.
• Many adaptations make insects
one of the most successful
terrestrial animals.
– Exoskeleton for water conservation
– Tracheal System for gas exchange
– Metamorphosis
– Many types of mouth parts
– Flight
Subphylum Myriapoda
• Myriad, ten thousand +
podus, foot; millipedes
and centipedes.
• Two tagmata (head and
trunk)
• All are terrestrial
Class Diplopoda – The Millipedes
• Have 11 – 100 trunk segments, each with two
pairs of appendages.
• Each segment is actually the fusion of two
segments; internally there are two ganglia,
two pairs of ostia, etc. in each segment.
• Most are round.
• Feed on decaying plant matter.
• Roll into a ball for defense.
• Some excrete hydrogen cyanide as a deterrent
to predators.
Giant African Millipede
See it move!
Class Chilopoda – The Centipedes
• 15+ trunk segments, each with a pair of legs.
• Flattened body
• Last pair of legs is modified into long sensory
appendages.
• Nocturnal predators
• Poison claws (maxillipeds) on first segment
capture other invertebrates and small
vertebrates.
• Males lay down a silk web and places a
spermatophore for female.
Predatory Centipede vs. Mouse
Subphylum Hexapoda
• Class Insecta
– three tagmata (head, thorax, and abdomen)
– Five pair of head appendages
– Three pairs of legs on thorax
Specialized Mouthparts
• Modified mouthparts
have allowed insects
to diversify and take
advantage of many
different food sources.
• Modify generic
structures for various
food sources.
Generalized Insect
Mouthparts
Chewing Mouthparts
Piercing Mouthparts
Siphoning Mouthparts
Sponging Mouthparts
Antennae
Modifications
Insect Flight
• Direct or Synchronous Flight – muscles attach
at the base of wings contract for downward
thrust and muscles attach to the exoskeleton
contract for upward thrust. Requires two
nerve impulses for upward and downward
strokes. Ex. Butterflies, dragonflies,
grasshoppers.
• Indirect or Asynchronous Flight – muscles act
to change the shape of the exoskeleton for
both strokes. Only one nerve impulse for 50
cycles. Ex. Flies and wasps.
Indirect Insect Flight
• Indirect flight muscles allow wings to beat faster than
neural transmission.
• Dorsoventral and longitudinal muscles.
• Flexible thorax.
Review of Insect Physiology
•
•
•
•
Digestion – three part tract.
Respiration – most use a tracheal system
Circulation – open circulatory system
Nervous – ventral nerve cord with some
segmental ganglion.
• Excretion – Malpighian tubules with uric acid.
Tracheal Systems in Insects
• The tracheal system of insects
– Consists of tiny branching tubes that penetrate the body
Air sacs
Tracheae
Spiracle
(a) The respiratory system of an insect consists of branched internal
tubes that deliver air directly to body cells. Rings of chitin reinforce
the largest tubes, called tracheae, keeping them from collapsing.
Enlarged portions of tracheae form air sacs near organs that require
a large supply of oxygen. Air enters the tracheae through openings
called spiracles on the insect’s body surface and passes into smaller
tubes called tracheoles. The tracheoles are closed and contain fluid
(blue-gray). When the animal is active and is using more O2, most of
the fluid is withdrawn into the body. This increases the surface area
of air in contact with cells.
• The tracheal tubes
– Supply O2 directly to body cells.
Body
cell
Tracheole
Air
sac
Trachea
Tracheoles
(b) This micrograph shows cross
sections of tracheoles in a tiny
piece of insect flight muscle (TEM).
Each of the numerous mitochondria
in the muscle cells lies within about
5 µm of a tracheole.
Body wall
Air
Mitochondria
Myofibrils
2.5 µm
Tracheal System Limits Size
See the Giant Weta
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Insect Excretion
3 Kinds of Insect Metamorphosis
• Ametabolous Metamorphosis – only
difference between larvae and adult are size;
both are wingless. Silverfish, Order Thysanura.
After Flight…
• Hemimetabolous Metamorphosis – develop
from egg to adult has several stages (instars)
with smaller versions of adults called nymphs.
Immature nymphs have no wings or genitalia
until adult.
3 Kinds of Insect Metamorphosis
• Holometabolous Metamorphosis – after
hatching from egg, immatures are called larvae
(very different body form than adult). After
several instars, the last larval molt forms a
pupa – undergoes radical body form change.
– Protective case may enclose pupal stage:
• Moths use silk to make a cocoon.
• Butterflies use the larval exoskeleton to make a
chrysalis.
• Adult emerges from case very different in body
form – eclosion.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Incomplete or Hemimetabolous Metamorphosis
From Hickman/Roberts/Larson, Integrated Principles of Zoology, 11th ed., Copyright © 2001 The McGraw-Hill
Companies.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Complete or Holometabolous Metamorphosis
From Raven/Johnson, Biology, 3rd ed., Copyright © 1999 The McGraw-Hill Companies.
You Decide?
Hemimetabolous - insects hatch looking much
like adults. Nymphs gradually attain adult form
and wings.
Holometabolous - young very different from
adults. Pupal stage metamorhosis into adult.
Insect Orders
Order Collembela
• Antennae with 4-6
segements
• No compound eyes
• Six segments in
abdomen
• Furcula for jumping
• No wings
• Springtails
Order Thysanura
• Tapering abdomen
• Long antennae,
scaled on body
• No wings
• Silverfish
Order Odonota
• Elongate,
membraneous wings.
• Long, slender abdomen
• Large compound eyes
• Dragonflies,damselflies
Order Mantodea
• Long prothorax
• Legs armed with
spine for grasping
prey
• Mantids
Missouri Native –Chinese mantis,
Tenodera aridifolia
Blattaria
• Oval, flattened
body
• Head concealed by
an extension of
prothorax
• Cockroaches
Order Orthoptera
• Long, narrow
forewing
• Hindwing is
broader
• Chewing
mouthparts
• Grasshopper
Order Dermaptera
• Elongate, chewing
pouthparts
• Abdomen with
unsegmented
forcepslike cerci
• Short wings
• Earwigs
Order Isoptera
• Workers are white
and wingless
• Abdomen broadly
joins thorax
• Reproductive forms
with wings
• Termites
Order Hemiptera
• Piercing-sucking
mouthparts
• Wings membraneous
– Basal portion is
leathery
– Apical portion of wing
is membranous
• Cicadas,
leafhoppers,
aphids
Order Coleoptera
• Hard front wings meet
midline to form a
cover (elytra)
• Hindwings
membranous
• Chewing mouthparts
• Beetles, largest insect
order; 350,000+
species
Order Lepidoptera
• Wings are broad and
covered in scales
• Mouthparts form a
sucking tube
• Butterflies and moths
Order Diptera
• One pair of welldeveloped wings,
other pair reduced
to knoblike halteres
• Mouthparts
variously modified,
but never chewing.
• Flies
Order Hymenoptera
• Four membranous
wings
• Well-developed
ovipositor,sometimes
modified into a sting
• Mouthparts for biting
and lapping.
• Social and solitary
forms
• Bees, wasps, ants
Order Phthiraptera
• Small, wingless,
ectoparasites
• Dorsoventrally
flattened
• Sucking/chewing
mouth parts
• Lice
Order Siphonaptera
• Flattened laterally
• Sucking mouthparts,
ectoparasites
• Jumping legs
• Fleas
The End
What order am I?