Entom 2010- Prelim I

Why is it important to understand the form and function of insects?

Insect identification

insect physiology

insect ecology

insect behavior

insect pest management

What adaptations of morphological features have made insects so successful on land? Which features were most significant to their success?

Metameric to tagmatic segmentation

Exoskeleton composed of chitin; waterproof wax layer

Wings

Mouthparts- diet breadth

Metamorphosis

Small size

List and describe the basic elements common to every insect body segment?

- paired nerve ganglia

- jointed appendages (mainly head and thorax)

- sclerites, separated by parts of membrane

- muscles

- coelomic spaces (digestive tract and heart included)

Explain in general terms why insects are (comparitively) stronger than humans

power: mass ratio increases as size decreases so the smaller you are the more powerful you are

What are the two major chemical components of insect cuticle? How do these components impact the insect exoskeleton?

- chitin and protein

- protein embedded in chitin matrix makes exoskeleton rigid

What are the advantages to insect cuticle?

- prevents water loss due to wax layer

- skeleton- muscle attachment support for locomotion

- sometimes stores waste material

- armor/ mechanical protection

What are the disadvantages of insect cuticle?

- limits growth; confines size of internal organs and muscle

- requires periodic shedding for growth which means there is a short- term vulnerability

What are the stages of insect molting? What hormones control this process and how (in general terms)?

How do insects get bigger?

By molting or shedding their skin

What are the three primary body segments of the insect body?

Head, thorax, and abdomen

How many legs does an insect have and where are the legs located?

Insects have six legs and they are located on the thorax

Where are the wings attached to the body? How many wings? What are the wings made from?

The wings are attached to the thorax. 4 wings (2 pairs) and they are made from cuticle

What kinds of eyes do insects have? How many eyes?

They have compound eyes; 2

Label and describe the insect leg: coxa, trochanter, femur, tibia, tarsus

from bottom to top: Tarsus, tibia, femur, trochanter, coxa

Describe the digestive system. Make sure to include the hindgut midgut, and foregut and the main functions of each. What is the function of the crop and proventriculus? Where are nutrients absorbed?

One hollow tube

foregut- midgut- hindgut

foregut- contains the crop which is used for storage

midgut- digestion and absorption

hindgut- excretion

Proventriculus- grinds and strains food (for solid food diet)

Describe the insect excretory system. What organ filters nitrogenous wastes? what are the three main parts of the gut and what functions does each serve?

The excretory system is foe excretion and osmoregulation.

- The Malpighian tubes filter nitrogenous waste into a primary urine

Describe the insect circulatory system. What does the insect heart look like? Where is it located? What is haemolymph? How does the insect circulatory system contrast with that of humans?

Insect "open" circulatory system.

It looks like one vessel (tube) (dorsal heart and dorsal aorta)

It is located longitudinally through the thorax and abdomen

Haemolymph is insect blood

- Humans don't have a longitudinal tube, takes longer for insect blood to circulate (5-8 minutes), humans are 20 seconds

Describe the insect respiratory system. Make sure to include tracheae and spiracles. How does gas exchange work in insects? How does the insect respiratory system contrast to that of humans?

- tracheae- internal air- filled tubes (invaginations of the cuticle) used for gas exchange; lined with chitin and must be shed with each molt

- Spiracles- where air enters and then is distributed by a network of tracheae (muscle controlled)

Describe the insect nervous system. Include the paired ganglion, ventral nerve cord, optic nerve brain, etc

* Brain- includes the optic nerve, has nerves for antennae, and processes most nervous signals from the body

* ventral nerve cord- has paired cord, contains the ganglion

How does the parasitoid jewel wasp "hijack" the cockroaches brain?

it injects venom through the neck directly into the cockroaches brain

Where is the walking pattern generator located in a cockroach?

How do insects compare in species with other animals in the world?

Most diverse

Insects represent how many of the animal species on Earth? On land?

Earth- 73%

Land- 85%

What is the most diverse insect order?

Beetles

Create a timeline with all major evolutionary events for insects identified. Explain how each of these events contributed to the success of insects

Devonian- Origin of hexapods

Carboniferous- origin of wings

Carboniferous- origin of wing folding

Carboniferous- origin of metamorphosis

End Permian extinction

Cretaceous radiation

Which insect orders are considered to be the most primitive?

APTERYGOTE ORDERS, Archaeognatha, Zygentoma

Which of the insect orders we learned are primitive hexapods and not actually insects?

Collembola

Finish the taxonomic classification of a Green Darner Dragonfly.

a. phylum: Arthropoda

b. class: Insecta

c. Order: Odonata

d. Family: Aeshnidae Genus: Anax

Species: junius

Name the apterygote orders that we've learned. What these orders look like?

In what sort of habitats would you find these primitive hexapods? What is ecologically significant about these orders?

1. Collembola, Archaeognatha, and Zygentoma

2. wingless, indirect fertilization, poor or no eyes

3. live in damp locations such as leaf litter or soil

4. provide important source of food for other insects

What was the special "new" feature possessed by the dragonflies, damselflies, and mayflies?

wing folding?

What were some of the advantages of the dragonfly and damselfly orders?

What is a possible explanation for so many gigantic insects in the Paleozoic era?

What is unique about the Neoptera (new wing) orders- why is this advantageous?

What is an ovipositor?

a tubular organ through which a female insect deposits eggs

In what ways has the ovipositor been modified?

? To allow for different types of penetration

Do all insects lay eggs or do some insects give birth to live young?

All insects do not lay eggs some give birth to live young

What is embryogenesis?

Embryonic development, the basic body plan of an insect is established such as segments, specialization of head, thorax, or abdomen

Define the following terms: Instar, Stadium, Eclosion, molt

Instar: growth stage also known as life stage

Stadium- the time between two successive molts

Eclosion- emergence from egg

Molt- periodic formation of new, larger cuticle and shedding of old cuticle

Do all insects have the same number of molts/ immature stages

No

What does it mean if an insect is "Ametabolous"? Which insect orders have ametabolous development?

no metamorphosis; apterygote insects (primitive)

What does it mean is an insect is "Hemimetabolous"? Which insect orders have this?

incomplete metamorphosis ***

What does it mean is an insect is "Holometabolous"? Which insect orders have this?

complete metamorphosis

What are imaginal discs?

a thickening of the epidermis of an insect larva, which, on pupation, develops into a particular organ of the adult insect.

Define the basic function of the following terms: PTTH, ecdysone, and Juvenile hormone

1. PTTH- releases molting hormone from an environmental stimuli

2. Ecdysone (molting hormone)- produced in prothoracic gland (developmental transitions)

3. Juvenile hormone- regulates post- embryonic development. Serves as a yes/no switch that tells cells in the insect's body what type of molt to undergo. it also inhibits the expression of adult features

How does the amount of juvenile hormone impact the developmental stage of an insect?

high JH- larval- larval molt

low JH- larval- pupal molt

no JH- pupal- adult molt

What starts the onset of a molt in some insects (e.g. Rhodnius kissing bugs)- what happens inside kissing bugs to stimulate the release of PTTH?

1. eating a blood meal

2. ??

List and describe the three properties that are important for walking

1. Speed: not just fast, but the ability to modulate speed

2. Directionality: steering toward resources or away from stress sources

3. Stability: limb movement has two phases; stance phase (on the ground) vs swing phase (off the ground)

Insects typically use their six legs in what type of gait? What are the benefits of using this gait?

What alternative gaits are suggested and why are they disadvantages?

1. Uncoordinated between segments

2. One segment moves supported by others- stable but slow

3. Side- to- side- fast but not stable

4. Alternating tripod- very stable, very fast (most used gait)

Know the importance of the following features: pleural suture, notum, pleural wing process

1. notum: provide a reinforcing basis of attachment for the wings

2. pleural suture: separates mesopleuron and metapleuron

3. pleural wing process: dorsal end of the suture used in wing articulation

What is the difference between indirect and direct flight muscles? How are they involved in insect flight?

1. indirect flight muscles: flap the wings but are not attached to them, deform the thorax(asynchronous)

2. direct flight muscles: control direction; pull on small bits of cuticle at the wing base

- Contraction of direct and indirect muscles provides lift and thrust

Describe how an insect's dorso- ventral muscles and dorso- longitudinal muscles are used to flap its wings

1. When dorso- ventral muscles contract, top of thorax is pulled down (wing goes up)

2. When dorso- longitudinal muscles contract, thorax is squeezed front to back, top pops up, wings go down

How are some insects capable of extremely fast wing beat frequencies?

Some insects can have their indirect flight muscles contract multiple times on a single nerve impulse

Wha are sensillae? What kinds of information can they provide to insect?

1. Sensilla are tiny organs n the outer surface of the exoskeleton that are connected to sensory neurons

2. They can provide sensory information (touch, taste, temperature)

What is the difference between hair- like sensillae and dome- like sensillae?

What is proprioreception? How can an insect tell if it's upside down?

Self- perception receptors;

What is a chordotonal organ? What sensory information is it designed to perceive?

They are sensillae that are invisible from the outside. They detect cuticular deformation/ stress

What is a subgenual organ? What kinds of sound vibrations does it receive? What kinds of insects have this organ?

It is located on the tip of the tibia of each leg and is involved with substrate vibration perception

What is a Johnston's organ? Where is it located? How does it function? What kinds of insects have this organ?

An organ at the base of the antennae; it detects flight speed by air movement deflection, males and midges

What is a tympanal ear? What insect orders have tympanal ears? Are tympanal organs always located on the same place on an insect?

complex ears of some insects, thin cuticle backed by air sac (modified trachea), they are not always located on the same places; Diptera, Orthoptera, Neuroptera, Mantid, Lepidoptera, Homoptera,

Describe how nocturnal moths react to different pulse rates of bat echolocation sounds?

Nocturnal moths will react to pulse rates by bats to know their intentions; widely spaced pulses (bats aren't hungry), rapid pulses, (bats are honing in on prey) moths will stop beating their wings and plummet downward

What are some reasons that insects might need to perceive sounds?

To know if there is predator or prey nearby, for communication, courtship

How do the cerci on the end of a cockroach's abdomen work?

they are covered with wind sensitive hairs and can detect air disturbances that may signal a predator, it sends the signal to the CNS

How do crickets and katydids produce sound? How do cicadas produce sound?

Cicadas produce sound on their thorax (sounds like clicking)

What are some advantages and disadvantages of communicating by sound (acoustical communication?)

Advantages: works any time (day or night), goes in all directions

Disadvantage: takes energy, public (could attract enemies), satellites

What is a chemoreceptor? How does it work?

A sensory organ that responds to chemical stimuli by entering the pore, the receptor on dendrite sends signal to sensory neuron which will then cause the mouth or ovipositor to taste/ contact chemoreception

What are pheromones?

within- species chemical communication

How do moths use pheromones? How do male moths find female moths?

They use pheromones for mating; the females release the pheromones from a particular location and the male moths fly towards it

How can male moths detect such minute amounts of female sex pheromone?

Have enhanced sensitivity with their feathery antennae

List and define the 4 different uses of pheromones we talked about

1. mating pheromone

2. alarm pheromone

Know where the contact chemosensory organs (taste receptors) are located on some butterflies, wasps, and cockroaches

1. cockroaches- mouthparts

2. Wasps- antennae

3. Butterflies- tarsi (feet)

What are compound eyes? Ocelli? Genitalic photoreceptors? Stemmata? What kinds of insects have these visual organs?

1. Compound eyes- eyes that form images (adults)

2. Ocelli- simple eye; light sensitive but not image forming, detects light levels

3. Genitalic photoreceptors- only in Lepidoptera, sense light

4. Stemmata- (only in holometabolous larvae) structurally similar to the individual ommatidia of the compound eye, perceives color, form, distance, and polarization

What is ommatidium? Generally, how does it work? Are all ommatidia the same size? Why would they be different in size?

1. Ommatidium- they are what is in compound eyes

2. it focuses light, forms cone- shaped rhabdom, and the pigment cells limit light movement between neighboring ommatidia

What keeps light entering one ommatidium from going into adjacent ommatidia?

How does insect ecology and biology impact eye size and position?

What is a pseudopupil?

it comprises ommatidia in which their optical axes are directed at you

Define the inner- ommatidial angle. Whys is this important to insect eyesight?

It determines how acute their vision is (higher acuity when eyes are directly in from of your head)

Relative to humans, do insects have better or worse eyesight?

worse

How do widely spaced eyes improve depth perception?

How does spectral sensitivity differ between insects and humans in general? What does this mean? What types of light can insects see that humans cannot?

They can do lower wavelengths (300-400, UV) They can see a glowing pollen trail (nectar guide)

Why do house flies perceive fluorescent light as if it were a strobe light?

they can detect movement with much greater sensitivity than humans (flicker fusion frequency)

What is sexual selection, compared with natural selection?

Evolutionary mechanism associated with sexual competition rather than survival

What is the difference between indirect and direct sperm transfer?

Indirect sperm transfer- (only the apterygote orders), usually involves complex courtship dances; will usually attach a spermatophore to a substrate

Direct sperm transfer- copulation (physical apposition of genitalia followed by sperm transfer

Which insect orders exhibit indirect sperm transfer Direct sperm transfer?

Indirect- apterygote order

Direct- all the others

What are some advantages and disadvantages of visual communication? Give some examples of this type of communication

Advantages: can be transmitted over relatively long distances, can be rich in information content, can be species specific, travels in straight line of sight, cheap

Disadvantages: can only be used during daylight, can be very public, can be blocked

Ex: a male flying upward with another showing color for attraction

What do Photuris fireflies do to earn the name "femme- fatale fireflies"?

They attract another species (Photinus males) and then eat them

What are some advantages and disadvantages of acoustical communication? Give some examples of this type of communicaion

Advantages: works anytime of day or night and goes in all directions

Disadvantages: costly to make sound (takes energy), public so could attract enemies and satellites ex crickets, katydids

How do insects differentiate between acoustical signals f another species? What is a "satellite male"?

frequency, pitch, etc. some insects may have calling song, courtship song, aggressive songs

A satellite male is a male that lurks near another insect that is calling and then mates with the approaching female

Give an example of olfactory communication

sex pheromones

What is a resource- defense based mating system? Give some examples of this mating system

defending or protecting a needed resource (ex: cicadas- males establish territories where virgin females emerge from the ground

What is sperm competition? What are some tactics male insects have utilized to ensure their sperm and not another male's sperm, would be used to fertilize a female's eggs?

sperm from 2 or more males compete to fertilize (prolonged copulation, sperm plugs, removal of sperm)

Describe some examples of female choice and gift- giving mating systems. What is spermatophylax? Why might male praying mantises allow themselves to be eaten by a female?

glandular secretions, prey/food, yourself

spermatophylax: a substance that is consumed during copulation, the larger the better

What is traumatic insemination? Which group of insects has this mating system?

hemiptera, takes dagger like penis and punctures cuticle

What is parthenogenesis?

reproduction from an ovum without fertilization, especially as a normal process in some invertebrates

What is meant by orientation?

the self controlled maintenance or change of an organism's body position relative to the surrounding environment

Define "kinesis" and understand the examples that were given

undirected reactions (room with blindfolded, cold people)

Define "taxis" and understand the examples that were given

directed reactions; side to side sampling of stimulus through time and directed movement in response

Be able to interpret the terminology for taxes and kineses (what is meant by a "positive chemotaxis", "negative phototaxis", or "positive photokinesis"?

Define "transverse orientation" and understand the examples that were given

position body at a fixed angle relative to stimulus

What is the difference between an innate behavior and a learned behavior?

innate behavior: develops independently of the environmental context; genetically programmed behavior, "hard wired"

learned behavior: develops as a result of experience; not genetically programmed; change in behavior as a result of experience and is stored in memory

Be familiar with the examples given of learning in insects (landmark learning, olfactory learning, etc)

bees learning landmarks, wasps use caterpillars wounding and chemical recognizance in leaves as a means of tracking it down