Introduction To Entomology

Question 1

How much of the worlds named species to insects account for?

Answer 1

60% approx 1,000,000 of 1.8 million named species

Question 2

Why are insects so numerous?

Answer 2

Size - size limited by exoskeleton, respiration and weight and thus limits food consumption and effects of predators
Exoskeleton - used for protection, water loss, attachment points for muscles (made of chitin and wax)
Flight - only inverts to fly, permits land expansion and escape. Twice as efficient as birds and mammals
Reproductive capacity - produce hundreds of eggs, store sperm, parthenogenetic
Metamorphosis - most insects go through metamorphosis
Adaptability

Question 3

What are the 2 types of metamorphosis?

Answer 3

Holometabolous - complete metamorphosis, life cycle has four stages egg, larvae, pupa adult. Includes beetles, flies, wasps, butterflies and wasps (80% of insects on planet)
Hemimetabolous - metamorphosis that has no pupal stage. Includes aphids, grasshoppers, cockroaches, mayflies and stoneflies

Question 4

When did Arthropoda and insects first appear in the fossil records?

Answer 4

600 Mya and 400mya

Question 5

What does the current view of arthropod evolution suggest?

Answer 5

Arthropoda evolved from Annelids (segmented worms) 600mya from the development of an exoskeleton secreted by the epidermis.

Question 6

What are the four phylum supposedly to have evolved from Annelids?

Answer 6

Trilobites
Chelicerates
Crustacea
Uniramia

Question 7

What did insects evolve from?

Answer 7

400/500 Mya insects evolved from myriapod ancestor

Question 8

Why are springtails debatable as to wither they are insects or not?

Answer 8

They are ametabolous like myriapods
They live in moist environments and lack wax layer or exoskeleton
The exchange gas directly with the environment
Externally fertilise

Question 9

Defining characteristics of an insect?

Answer 9

Exoskeletons
Body plan is head, 3 segmented thorax, 11 segmented abdomen 
Complete respiratory (tracheal) system with spiracles on body

Question 10

When did wings appear in the fossil record in insects?

Answer 10

380mya

Question 11

What reasons do humans have to use insects?

Answer 11

Food for species at other tropic levels
De composers
Pest control agents
Pollinators
Producers of products we use (silk, honey) 
Forensics

Question 12

Why are insects important in regards to disease?

Answer 12

Spread malaria (300,000 to 500,000 million cases worldwide) killing 1 million per year
Bubonic plague - spread by rat flea
Lyme disease - deer ticks spread this

Question 13

Why are insects important in terms of food production?

Answer 13

Rising human population sees an increase in demand for food

Pest species cause around a 20-30% loss of potential production of food

Question 14

What is a pest?

Answer 14

Any organism that constrains health, food production or cash generation

Question 15

What are the four reasons that a pest outbreak may occur?

Answer 15

Geographical movement
Agricultural development (mono cultures) 
Plant breeding/ cultivar selection
Destruction of natural regulatory mechanisms

Question 16

Why does geographical movement increase pest outbreaks?

Answer 16

Absence of natural enemies

Examples include Russian wheat aphid and Mediterranean fruit fly

Question 17

Why has agricultural development effected pest outbreaks?

Answer 17

Mono cultures - plants germinate together, grow at same time and are harvested together
Not only phenotypically identical but may also be genotypically identical
If an insect can feed in one plant it can feed in them all

Question 18

Why is plant breeding an issue in pest outbreaks?

Answer 18

Reductions in secondary plant substance to increase palatability and improvements in size of harvested plants

Question 19

Why has destruction of natural regulators affected pest outbreaks?

Answer 19

Most insects have their populations constrained by predators
Regulation can be upset by changes in farm practices (use of chemicals)
Pesticide can lead to outbreaks of secondary pests or resurgent pests

Question 20

Examples of mid 20th century chemical insecticides

Answer 20

DDT
Schradan
Allethrin
Carbaryl
Imadacloprid

Question 21

What are resurgent and secondary pests?

Answer 21

Most insecticides are non specific and so non target mortality rate can remove natural control
Many predators take longer to recover
Current estimates suggest 50% of pests worldwide are resurgent or secondary

Question 22

What are the four reasons to study insects?

Answer 22

Numbers
Use to humankind
Disease
Food production