Entomology Exam 1 (copy)

exoskeleton

1. protection from predators

2. waterproof

3. attachment of muscles

4. chemically resistant

exoskeleton has what chemical in it?

chitin (non digestive, very stable polysaccharide)

what does sclerotized mean?

insects whose exoskeletons have hardened through a biochemical process

why must exoskeletons be shed periodically?

so they have room to grow. insects grow in a stair-like fashion

digestive system

foregut, midgut, hindgut

foregut

mouth, pharynx, esophagus, crop: initial processing of food

midgut

major area of digestion and absorption of food

hindgut

process of waste, water retention, excrete or absorb

malpighian tubes

1. kidney of an insect

2. outgrowth from hindgut

3. removes nitrogenous waste (uric acid), balances salts, and gets rid of excess water

respiratory system

tracheal system:

1. branched tubes that connect to spiracles in body wall

2. terminal ends of tubes reach every part of the body

3. tracheal gills: specialized structures found in some aquatic nymph stages

why would the respiratory system limit the maximum size of insects?

the oxygen content of the world is much lower now and it would be hard for tracheal tubes to run throughout a bigger body

circulatory system

open system with hemolymph

1. transports nutrients, hormones, wastes

2. little role in respiration

3. linear hear extends the whole body

metamorphosis (simple)

incomplete. juveniles look like adults but smaller. juveniles are nymphs

metamorphosis (complete)

juveniles look very different from adults. juveniles are larvae (4 distinct stages)

ametabolous 

(wingless insects) no change between juveniles and adults

hemimetabolous

winged insects with aquatic nymphs have gills and look somewhat different (often called naiads)

paurometabolous

winged insects with terrestrial nymphs have an intermediate level of difference

ex) ocelli, wing pad growth

holometabolous (complete metamorphosis)

75% of all insects have this type of growth

have several instars: breaks down tissue back into stem cells then recreates the body— the life histories are different

know pupa and larvae

Order Diplura

• tiny (nearly microscopic) soil insects

• two caudal filaments (cerci)

• no eyes

• unusual in having numerous instars, sometimes over 30

Order Collombola

• Springtails

• abundant soil arthropods

• spring-like organ on abdomen: furcula

• collophore on ventral side: water balance

Apterygote Hexapods

possibly convergent evolution of:

1. six thoracic legs

2. two antennae

3. mandibulate mouthparts

no evidence of wings

ex) Diplura, Collembola

Ecology of Apterygote Hexapods

• important in soil ecology

• many feed on fungi

• others feed on detritus 

• some carnivores and herbivores

Order Thysanura

• Silverfish

• three caudal filaments

• secondarily wingless 

• possibly paraphyletic (common ancestor, but all the descendants aren’t the same”

Paleoptera

old-winged insects

cannot fold wings flat over their abdomen

Order Ephemeroptera:

• Mayflies

• pair of caudal cerci (paired appendages) and sometimes a single caudal filament

• sub-imago stage

• imago stage

sub-imago stage

penultimate stage with wings (only fleeting-winged insects)

imago stage

sexually mature stage. front wings are large, back wings are small

Mayfly Adults

• do not feed on algae

• veiny wings

• ancestral traits

Order Odonata

• large eyes

• front legs modified for capturing prey, lands with back legs

• four wings: large with numerous veins

• typically predatory nymphs

Order Odonata: Suborder Anisoptera

• dragonflies

• very fast

• wings held out from body (perpendicular, straight out like an airplane

• powerful, agile fliers, heavily built, can fly in any orientation

• predatory in both life stages

• were the largest flying insects that ever existed

Order Odonata: Suborder Zygoptera

• damselflies

• lightly built, but morphologically similar to butterflies

• wings are parallel to body

• generally weak fliers/slow

• eggs are laid inside plants which can cause damage (ecology)

What is an insect?

Six appendages on the thorax

Three body segments

Two antennae

Wings in the adult stage

vestigial

a structure like wings or a body part, that was once functional in ancestors but has become reduced in size and now serves little to no purpose in the modern insect.

Head of an insect

Probably formed by the fusion of multiple segments in some ancient ancestor

• One pair of antennae

• Mouthparts are often highly modified

• Always on the anterior

• simple eyes

• compound eyes

Antennae

• Primary sensory organs in most insects

• Tactile

• Smells chemicals (chemoreceptive)

Mouthparts

• Modified pared appendages

• Food manipulation and sometimes sensory

• Ancestral condition is madibulate 

  • Labrum

  • Labium

  • Maxillary 

How many segments form the head of an insect?

5 body segments fuse together to form the head of an insect

Thorax

• Three segments: prothorax, mesothorax, metathorax

• Each segment with one pair of legs

• 2nd and 3rd segment with wings (never on the prothorax)

Wings

only in adult stage (last instar - developmental period, insects are done growing after wings are present)

one exception: mayflies

Abdomen

• No appendages except in the genital appendages (most posterior)

• Contains the most digestive and reproductive organs

• In most species, in a relatively ancestral condition

Orthopteriod

Superorder, big group of multiple orders. Part of Neoptera

ancestral mouthparts with almost no modifications

many generalists

fold wings flat on abdomen

Order Orthoptera

• grasshoppers, crickets, and katydids

• two forms: hopping with enlarged femur/tibia or crawling (normal sized)

• prominent tympanum and sound production ability (legs or wings)

Order Mantodea

• praying mantises

• front legs raptorial to catch prey and hold stinging prey away from them

• elongated prothroax

• generalist predator: mainly carnivorous

• unmodified mouth parts

Order Phasmatodea

• walking sticks

• similar morphology as mantises

• all herbivorous 

• many toxic and highly camouflaged

• some secondarily wingless 

Order Blattodea

• cockroaches

• not monophyletic

• Dorso-ventrally flattened

• Expanded pro-thorax shield

• Most herbivorous or omnivorous. Some detritivores on dead wood.

• Closely related to mantises

• Only a few enter human dwellings

Infraorder Isoptera

• termites

• modified cockroaches

• eusocial: king, queen, workers, soldiers

• closely related to wood-eating cockroaches

• can live monogamously for 30 years

Hemiptera

• true bugs, lice, etc

• piercing, sucking mouthparts

  • feed on fluid: plant fluid, blood, hemolinth

• no cerci

• highly diverse group

• terrestrial and aquatic

Suborder Auchenorrhyncha

• Hoppers

• Short mouthparts that appear to emerge from posterior-ventral part of head

• Many adapted to hopping (predator escape mechanism)

• Some produce sound

• Many are disease vectors

• All herbivorous

Suborder Heteroptera

• True bugs

• Typically larger.

• Many herbivores, some carnivores, also some aquatics (carnivorous)

• Mouthparts long, appear to emerge from anterior part of head

Suborder Sternorrhyncha

• aphids and scale insects

• relatively immobile— missing wings and legs sometimes

• highly modified hemiptera 

• mouthparts similar to hoppersd

Medically Important Hemipteroids

• human lice

  • infect people around the world

  • resistant to many insecticides

• kissing bugs (hemiptera)

  • spreads Chagas disease

  • common in neotropics

Potyviruses

•Spread by aphids

•Major source of crop reduction/loss globally

•Often aphid load can be very low but still spread infections

ocelli

simple eye

cerci

a pair of appendages located on the posterior-most abdominal segment of many insects,

ex) mayfly nymphs

spiracles

the external openings of an insect's respiratory system, located on the thorax and abdomen, that allow air to enter the network of internal tubes called tracheae

parts of a leg?

claw, tarsus, tibia (tibial spurs), femur, trochanter, coxa

ovipositor

a specialized, tube-like organ in female insects used for laying eggs

instar

the developmental stage between two successive molts

furcula

the appendage springtails use to propel themselves into the air

bottom

collophore

a tube-like appendage on the underside of a springtail's (Collembola) first abdominal segment

top

compound eyes

eyes that are made of thousands of tiny individual units called ommatidia

gills

to facilitate gas exchange (taking in oxygen and expelling carbon dioxide) while the insect is underwater.

wing pads

external, undeveloped wings found on the immature stages of certain insects, particularly in hemimetabolous insects like grasshoppers and mayflies.

Mayfly nymphs

important to the ecology of many streams and rivers because the grazers feed on algae and control it

Class Arachnida, Order Araneae

• spiders

• narrow joint between abdomen and cephalothorax, make silk

Class Arachnida, Order Opiliones

harvestmen

looks like one giant segment, fused together

really long skinny legs

ex) daddy long legs

Class Arachnida, Order Acari

• ticks/mites

• abdomen joined very broadly to the cephalothorax

• modified sucking mouthparts for fluid

Subphylum Crustacea

• more than 8 legs

• has shells

• lobsters, crabs, crayfish, shrimp, copepods, barnacles, etc

Order Amphipoda

laterally flattened (side to side)

Order Isopoda

dorso-ventrally flattened (top to bottom)