Subphylum Hexapoda

Question 1

The Hexapod’s body is divided into _ tagmata?

Answer 1

3 tagmata:
-5 pairs of head appendages
-3 pairs of legs on thorax
-reduced abdominal appendage

Question 2

What are the 2 classes of hexapods?

Answer 2

Entognatha
Insecta

Question 3

What are pteryogotes?

Answer 3

winged insects

Question 4

What are apteryogotes?

Answer 4

wingless insects

Question 5

What adaptive traits contributed to insect dominance on land?

Answer 5

-exoskeleton (conserving water)
-evolution of flight/small size
-well protected eggs
-variety of structural/behavioral adaptations

Question 6

What are some common features of Class Insecta?

Answer 6

-sclerites (
-head (compound eyes)
-thorax (wings)
-abdomen (9-11 segments)
-antennae (touch, taste, hearing)
-legs (large variability)

Question 7

Another common feature of Class Insecta is mouthparts. What are the functions of:

Labrum
Mandibles
Maxillae
Labium
Hypopharynx

Answer 7

Labrum - upper lip for sensory
Mandibles - sclerotized for chewing
Maxillae - sensory, cutting surfaces, food-holding palps
Labium - lower lip with sensory palps for food holding
Hypopharynx - tongue-like sensory structure

Question 8

What are the 2 modifications of the mouthparts?

Answer 8

1. Sucking mouthparts - some variation in the basic structure
   mosquitoes - six stylets from labrum, hypopharynx, mandibles and maxillae used for piercing and sucking
   butterflies, moths - maxillae modified into long, coiled tube
2. Sponging mouthparts -labium expanded into soft labial lobes
   flies

Question 9

What is the hypothesis of the origin of flight?

Answer 9

-Wings may have evolved from gill-like lateral outgrowths of thorax
-Used for gliding and the ability to flap came later

Question 10

Most insects have two pairs of wings. Describe forewing/hindwing.

Answer 10

-Thin and membranous or Thick and hard
-Covered with scales or hairs

Question 11

What is Diptera?

Answer 11

True flies
-only has one pair of wings
-with halters

Question 12

Describe wing movements controlled by muscles in the thorax

Answer 12

locusts and dragonfly
-Indirect flight muscles contract which elevates wings
-Direct flight muscles contract which lowers wings

flies and midges
-longitudinal thoracic muscles contract and arch tergum

Question 13

Describe the process of synchronous flight

Answer 13

-single nerve impulse stimulates wing muscle contraction
-thus, one wing beat

Question 14

Describe the process of asynchronous flight

Answer 14

-depends on stored potential energy in tergum and specialized muscle fibers
-wing beats out of phase with nerve impulses
-allows very fast wing beats

Question 15

What are the different strategies aquatic insects use for gas exchange?

Answer 15

-diffusion across body wall
-bubble of air around spiracles
-tracheal/coxal gills

Question 16

Ametabolous metamorphosis (direct)

Answer 16

-both adults and larvae are wingless
-number of molts varies and continues after maturity
-body size and sexual maturity differs between adults and larvae

Question 17

Hemimetabolous metamorphosis

Answer 17

-series of molts from egg to adult stage
-nymphs gradually take on adult form
-nymphs are called naiads if aquatic, usually have gills

Question 18

Ecdysis

Answer 18

-necessary for increase in size
-old cuticle shed > growth > new cuticle > hardening
-molting animals grow in the intermolt phases or instars
-old cuticle shed by taking in water or air and increased blood pressure
-new cuticle formed prior to molt of old cuticle

Question 19

Describe intermolt phase or instars

Answer 19

soft tissue increases in size until there is no space within the cuticle

Question 20

Explain ecdysis and formation of new cuticle under hormonal control

Answer 20

-PTTH produced by neurosecretory cells in brain and ganglia
-Prothoracic gland
-Ecdysone(molting hormone is produced
-Formation of new cuticle and ecdysis