External Morphology

Question 1

define exoskeleton/cuticle

Answer 1

• skeleton on the outside
• it is comprised of hard segments connected by a flexible membrane

Question 2

cuticle function

Answer 2

• Color and texture display
• Contains internal organs
• Attachment/anchor for muscles -> movement
• Base for sensory organs
• Water retention

Question 3

cuticle function - movement and flexibility

Answer 3

• Flies (Diptera) and some others use the cuticle to power wings
• Indirect flight muscles attach to thorax, not wings. Muscles flex thorax, thorax flaps wings

Question 4

cuticle function - water retention

Answer 4

• the cuticle is covered with waxy hydrocarbons to prevent water loss
• Insects are small: not much water to lose
• Small size = high surface area to volume ratio. This means even more water loss

Question 5

segmented body plan

Answer 5

• head
• thorax
• abdomen

Question 6

segmented body plan - head

Answer 6

• feeding and sensory input
• sensory organs
• Mouthparts

Question 7

head - sensory organs

Answer 7

• antennae
• compound eye
• ocelli

Question 8

head: sensory organs - antennae

Answer 8

• tactile and chemosensory
• Organs of touch and smell

Question 9

head: sensory organs - compound eye

Answer 9

• image forming
• integrates images from multiple facets called ommatidia

Question 10

head: sensory organs - ocelli

Answer 10

• there are 3
• simple eye (as in, not compound)
• Senses light and motion

Question 11

head: mouthparts - types of mouthparts

Answer 11

• Mandibulate (mandibles)
• Sponging
• Piercing-sucking
• Lepidoptera proboscis
• Multi-purpose bee mouthparts

Question 12

head: mouthparts - mandibles

Answer 12

• often used for chewing, manipulation
• Labrum, maxilla, labium: generally used for getting food into mouth

Question 13

head: mouthparts - Sponging mouthparts

Answer 13

Pseudotrachea are grooves on the labellum that suck up liquid via capillary action

Question 14

head: mouthparts - Piercing sucking

Answer 14

• Mosquito example: pierce host, then suck blood
• Mouthparts have been modified to form a straw to deliver saliva and suck liquid
• other organisms can pierce plants (sap), vertebrates (blood), or prey (suck out guts)

Question 15

head: mouthparts - Lepidoptera proboscis

Answer 15

Specialized mouthparts of butterfly

Question 16

head: mouthparts - Multi-purpose bee mouthparts

Answer 16

• Mandibles and siphon: Can be used for building
• function is helped by lapping with hairs on glossae
• Some bee “tongues” are so long that they extend beyond the end of the abdomen

Question 17

segmented body plan - thorax

Answer 17

• used for locomotion
• Legs
• wings

Question 18

segmented body plan: thorax - legs

Answer 18

• Modifications
• Tripod gait for walking

Question 19

thorax: legs - modification

Answer 19

• thorax has three segments
• Fore legs (prothorax)
• Mid legs (mesothorax)
• Hind legs (metathorax)

Question 20

thorax: legs - tripod gait

Answer 20

two legs on one side, one on the other, and alternate so body is always supported by a tripod

Question 21

thorax: wing - modification

Answer 21

• Elytra
• Hemielytra
• Minute (small/tiny) insects
• No wings

Question 22

wings - elytra

Answer 22

• Forewings are armor
• ex: beetles (coleoptera)

Question 23

wings - hemielytra

Answer 23

• Anterior part of forewings are armor
• true bugs (Hemiptera)

Question 24

wings - minute insects

Answer 24

• Wings swim through air – analogous to oars
• Example: thrips (Thysanoptera)

Question 25

wings - no wings

Answer 25

many insects have no wings or lose wings after dispersal

Question 26

wings - no wings example

Answer 26

Bristletails, lice and fleas

Question 27

wings - no wings after dispersal example

Answer 27

Ants and termites

Question 28

segmented body plan - abdomen

Answer 28

• Dorsal segments are tergites
• Ventral segments are sternites
• digestion and reproduction
• ovipositor

Question 29

abdomen - ovipositor

Answer 29

• Injects eggs into host organism (caterpillar) or substrate (plant)
• Secondarily modified into stings in bees, ants, and aculate wasps (hymenoptera)