W11, Arachnids, Insecta

Question 1

Describe the basic biology of Chelicerata

Answer 1

• Two main body parts
  
  • Cephalothorax
  • Abdomen
• No antennae (can sometimes use to
• Six pairs of appendages
  
  • Chelicerae (bear the fangs)
  • Pedipalps
  • Four pairs of legs
• Terrestrial and marine

Question 2

How do you distinguish between arachnids vs insects?

many spiders look like ants as a defence strategy

Answer 2

• # body parts
  
  • arachnids have 2 main body parts
  • insects have 3; a dinstinct head, thorax, and abdomen
• Appendages
  
  • chelicerae (fangs) and pedipalps
    
    • insect mouthparts are highly modified and can look similar, so they’re not a good use for ID
  • antennae
    
    • all insects have antennae
    • arachnids have no antennae
  • # pairs of legs
    
    • arachnids have four
    • insects have 3
  • wings
    
    • arachnids have no wings
    • insects often have 1 or 2 pairs of wings

Question 3

What are Aranae?

Answer 3

Spiders

Question 4

What is it that makes Aranae different from other Arachnids?

Answer 4

Spinnerets (produce silk)

on the abdomen

Question 5

In Aranae, what are the chelicerae commonly known as?

Answer 5

Jaws with piercing fangs

Question 6

In male Aranae, what are the pedipalps evolved for?

Answer 6

Mating.

The male redback has an unusual spiralled pedipalps.

Question 7

Decribe the eyes of spiders

How many do they normally have?

Are they simple or compound?

Arrangement?

Answer 7

Normally have 8

Eyes are simple - only have one facet

Arrangement can be important for ID

Question 8

What are the pedipalps evolved to be in scorpions?

Answer 8

Pincers

Question 9

What is the group that mites and ticks are in?

Answer 9

Acari

Question 10

What is the distinguishing feature of Acari

(mites and ticks, if you don’t remember)

Answer 10

Loss of visible body segmentation

Question 11

What are mites good at controlling, in terms of biological control?

Answer 11

Other mites and thrips.

Question 12

What are the chelicerae evolved to do in ticks?

Answer 12

To cut skin.

Question 13

What’s the difference between hard and soft ticks?

Answer 13

Hard ticks

• feed once during each stage then leave their host

Soft ticks

• live in close association with their host
• feeds repeatedly during a particular life stage

Question 14

What are the morphological features that distinguish Hexapoda (and therefore Insecta)?

Answer 14

• The main body sections
  
  • head, thorax, abdomen
• Antennae
• Three pairs of thorasic legs
  
  • Hexa = six, poda = foot

Question 15

What are collembola, what are their biological features, and give an example of one that’s a significant agricultural pest.

Answer 15

Collumbola = springtails

• Tubular appendage (collophore) that holds the ‘springtail’ (Furcula)
• primarilly detritivores and microbivores
• commonly found in leaf litter and other decaying material
• highly sensitive to dessication
• moult repeatedly during their life, even as adults

The lucerne flea is the only pest species of Collumbola

• not just lucerne; also canola, field peas, lupins, faba beans
• crops are most susceptible following seedling emergence
• eggs hatch with soaking autumn rains
• 3-5 generations through autumn-spring
• diapause eggs laid when conditions get hot and dry

Question 16

Describe the biology of insects

Answer 16

Antennae

Three body parts

• head, thorax, abdomen
  
  • thorax is divided into three sections, and each section has a pair of legs attached

Three pairs of legs

Up to two Wings

• Evolved as an extension of the cuticle, and thought to be originally for absorbing heat rather than flying
• might be difficult to see or evolved to look/

Compound eyes AND up to three simple eyes (ocelli)

• Compound eyes made of repeating units

Exoskeleton

• can have bits of the exoskeleton that is hard and rigid and bits that are flexible

Diverse mouthparts

Presence of a cercus

Question 17

What are the three sections that the insect digestive system is broken up into?

Answer 17

Foregut, midgut, hindgut

Question 18

Describe the respiratory system in insects

Answer 18

Spiracles are openings in the abdomens of insects that draw air in

The respiratory system delivers oxygen directly to the cells that need it because the circulatory system is open (i.e. the haemolymph just flows through the body cavity, so if the respiratory system wasn’t closed, the haemolymph would leak out the spiracles).

Question 19

Describe the difference between gradual (simple, incomplete) and complete metamorphosis

Answer 19

Gradual

• Immature stages resemble adults
• Only adults have wings and are able to reproduce
• Usually feed on the same foods and are found in the same environment during the different stages

Complete

• Immature stages look nothing like the adults
• To go from the larval stage to the adult requires a complete change in morphology
• Only adults have wings
• Number of instars varies
• In many species, the different stages feed on different foods and occupy different niches

Question 20

What are Blattodea and what are some distinguishing features?

Answer 20

Cockroaches

• Oval, flattened body
• Head is concealed beneath the pronotum (looks like a shield)
• Manibulate (chewing) mouthparts
• Antennae
• Wing development varies

Question 21

What are Phasmatodea and what are some distinguishing features?

Answer 21

Stick insects

• mimick sticks or leaves
• mandibulate mouthparts
• all legs adapted for walking
• vegetarian
• some species are significant pests

Question 22

What are Orthoptera and what are some distinguishing features?

Answer 22

Grasshoppers, crickets, katydids

• hindlegs adapted for jumping (i.e. they’re big and muscley)
• filiform antennae (thin)
  
  • short = locusts and grasshoppers
  • long = crickets and katydids
• mandibulate mouthparts

locusts

• form swarms and marching/hopping bands (as nymphs)
• once they’re swarming, its too late for control due to their ability to migrate LONG distances very quickly
• egg pods can reach densities of 500/m2
• moisture stimulates egg development
• eggs laid in autumn enter diapause