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me to
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nciples off
Entom
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molo
ogy!
ENY 3005/500
3
06 Cours
se Packe
et and Sttudy Guides
Addiitional re
eadings/m
media wiill be possted on w
website sseparate
ely
Dr. Miller ENY3005/50
006 Principles of Entomology, Universityy of Florida WEEK
K 1: INSE
ECTS SIIGNIFIC
CANCE AND B
BIODIV
VERSITY
Y
Why stu
udy insects?
? ANSWER
R: to a close
e approxima
ation,
every life
e form on Earth
E
is as insect!!
i
•
•
•
•
•
•
In
nsects are by
b far the most
m
succes
ssful
organisms on
o this plane
et
There
T
are more
m
kinds of
o insects th
han any
other group of organism
ms
In
nsects dom
minate (in terms of num
mbers of
species and in numberrs of individuals) everyy
o Earth ex
xcept one…
… insects are
ecosystem on
e
not well reprresented in marine env
vironmentss
IN
NSECTS PLAY ESSENTIAL, IRR
REPLACEA
ABLE ROLE
ES IN ECOSYSTEM
FUNCTIONS
F
S:
o Nutrie
ent recyclin
ng – leaf litte
er, wood de
egradation, carrion & d
dung disposal,
soil aeration and
d turnover…
…
o Plant pollination and in som
me cases, sseed disperrsal
o Mainttenance of plant comm
munity com position an
nd structure. This occu
urs
through herbivorry, feeding on plant tisssues and sseeds.
o Supporting insec
ctivorous animals – inccluding ma
any birds, m
mammals,
reptile
es, and fish
h.
In
nsects also lead to billions of dollars in crop losses eacch year.
o Pestic
cide use is often relied
d upon to
contro
ol pest inse
ect populations and to
protect food for humans.
o Problem: Pesticiides are ha
armful to
ecosy
ystems and
d humans. High
H
dosess can
be ca
arcinogenic or neurotoxic. Many
anima
als accumu
ulate pesticiide residue s in
their fatty
f
tissues
s. ƒ New resu
ults show th
hat low leve
el
exposures (tiny, tiny
y amounts) can be veryy dangerou
us to infantss
ses because
e pesticidess can mimicc the action
n of hormon
nes.
and fetus
These can lead to de
elayed effe
ects (brain d
damage, reduced I.Q.,,
nervous and
a other problems)
p
In
nsect vector many hum
man and liv
vestock dise
eases
Dr. Miller ENY3005/50
006 Principles of Entomology, Universityy of Florida Beneficial Impacts of Insects
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•
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•
They pollinate our crops
They provide products we use including honey, silk,
shellac, dyes, and chitin
Insects are food sources to many humans. 500 species
of insect from more than 70 families are used as food for humans.
Drosophila fruit flies, as a model system, has taught us a tremendous amount
about human genetics, development, behavior, neurobiology, etc.
Yet, despite all these obvious reasons to care about insects
Insects as a group are very poorly understood!
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•
Insect biology represents a frontier of science
Most species are not even described, let alone understood. The biology of even
the described species are often totally unexplored.
More details on…
The Mopane Worm:
Mopane worms are actually caterpillars, larvae of emperor moths, especially Imbrasia
belina, found across much of southern Africa. You can pick some up at the local market
in many areas. The caterpillar lives on mopane trees (Colophospermum mopane),
which are common. Early-instar larvae forage in aggregations of up to 200 individuals.
They can defoliate entire trees. This abundant food source is an important source of
protein for rural populations and can prevent malnutrition. People prepare these
caterpillars by gutting them and then drying them. They are sometimes canned or
available dried in bulk. Harvesting and selling mopane larvae provides a cash input into
rural economies. In fact, a month of harvesting the larvae can generate as much money
as a year’s minimum-wage income.
Mopane woodlands are prime elephant habitat. When elephants damage trees (which
happens a lot!), termites often hollow out the trees, producing a hollow, but living tree.
Ants will nest in the hollow trees and protect the trees from further herbivory from
elephants and humans. Native bees use the resin from damaged trees for their nests.
Thus, conserving mopane woodlands helps a variety of arthropods, elephants, humans,
and other animals.
Dr. Miller ENY3005/5006 Principles of Entomology, University of Florida Mopane Worm. From
http://lodges.safari.co.za/African_Travel_Articlestravel/mopane-worms_gallery.html. Mopane worms are
prepared in a variety of ways. After being dried, they are
often fried and served with a sauce such as tomato,
chili, cheese or peanut.
Have you ever eaten an insect? What about
other arthropods, such as lobster or crab?
Many insects are very nutritious, inexpensive, and delicious. The fact that many people
are squeamish about eating insects is unfortunate and not always logical.
SOME BASICS ABOUT INSECTS
Insecta is a class in the phylum Arthropoda (the arthropods). Other animal phyla include
the Chordata (vertebrates), the Nematoda (nematodes), and Annelida (segmented
worms). Other classes within the arthropods include the Chelicerata (spiders, mites,
ticks, horseshoe crabs, etc.), Myriapoda (millipedes, centipedes, etc.), and the
Crustacea (shrimps, lobsters, isopods, barnacles, crabs, etc.).
The word arthropod means “jointed feet”. Arthropods are defined as those invertebrate
animals with jointed limbs, segmented bodies, and exoskeletons made of chitin.
Hexpods include Insects, Collembolans, Diplurans, and Proturans. These are the sixlegged arthropods and are monophylogenetic (come from a common ancestor).
Please visit www.tolweb.org to learn more about the evolutionary relationships and
taxonomy for Arthropoda and other animals.
Insect Characteristics (from tolweb.org)
Insects have a large number of unique, derived characteristics, although none of these are externally
obvious in most species. These include (Kristensen, 1991):
•
•
•
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lack of musculature beyond the first segment of antenna.
Johnston's organ in pedicel (second segment) of antenna. This organ is a collection of sensory
cells that detect movement of the flagellum.
a transverse bar forming the posterior tentorium inside the head
tarsi subsegmented
females with ovipositor formed by gonapophyses from segments 8 and 9
annulated, terminal filament extending out from end of segment 11 of abdomen (subsequently
lost in most groups of insects)
In sum, insects share many unique features in common that might not be obvious to the
casual observer. Look under a microscope, and you can easily be trained to see the
differences!
Dr. Miller ENY3005/5006 Principles of Entomology, University of Florida Within insects, there are a couple of major divisions.
Here Zygentoma is called Thysanura – don’t worry about it, this is one of those areas of
uncertainty, stick with the class Hexapod order guide. The orders Archaeognatha and
Zygentoma (Thysanura) do not have wings. That is a major difference with the rest of
the insects. They are also ametabolous (and some have many, many molts!)
Some terms (also defined on Hexapod order guide)
• Ametabola – “without metamorphosis” ; eggs hatch into young which are smaller than
adults, but similar in appearance.
• Hemimetabola – have development in which the body form gradually changes at each
molt; incomplete metamorphosis
• Holometabola – development in which the body form abruptly changes at the pupal
molt; complete metamorphosis.
• Apterygota – without wings
• Pterygota – with wings
• Paleoptera – the primitive groups of winged insects (most extinct) that lack the ability
to fold the wings over the abdomen
• Neoptera – the orders of winged insects that can flex their wings over their abdomens
Dr. Miller ENY3005/5006 Principles of Entomology, University of Florida The reading for Week 1:
Wilson, EO, 1987. The little things that run the world. Conservation Biology 1, pp.
344–346.
Nelson, CR, 2001. Insects in The Encyclopedia of Evolution V. 2. M. Pagel, ed.
Oxford University Press, Oxford.
Available on the course website.
WEEK 1: INSECT SIGNIFICANCE AND BIODIVERSITY Study Questions and Objectives Based on course materials:
• Name the four major roles that insects play in ecosystems
• Explain where the mopane worm can be found (geographically and ecologically)
and how it is used by humans.
• According to E.O. Wilson, how many species of insects, and beetles specifically,
have been described? How many vertebrate species of been described?
• Explain, based on E.O. Wilson’s writing, what would happen if all invertebrates
suddenly disappeared from the earth.
• How many species of insects probably exist on Earth?
• Give six hypotheses for the numerical dominance of insects on Earth.
• List the four insect orders with the most species
• Know how to write scientific (latin) names, including order and family
• Name the major ecosystem with the fewest insects.
• Name six important uses of insect and insect products by humans.
• In what period of time, and how long ago, do we find the first fossils with wings?
Active flight has evolved at least four times in animals, including which groups?
(Nelson reading).
Study Terms
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•
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•
Tagmatization (defined in the Nelson reading)
Ametabola (also ametabolous), Hemimetabola (hemimetabolous), Holometabola
(holometabolous)
Apterygota, Pterygota
Paleoptera, Neoptera
Dr. Miller ENY3005/5006 Principles of Entomology, University of Florida