Introduction To Entomology Flashcards
How much of the worlds named species to insects account for?
60% approx 1,000,000 of 1.8 million named species
Why are insects so numerous?
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
What are the 2 types of metamorphosis?
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
When did Arthropoda and insects first appear in the fossil records?
600 Mya and 400mya
What does the current view of arthropod evolution suggest?
Arthropoda evolved from Annelids (segmented worms) 600mya from the development of an exoskeleton secreted by the epidermis.
What are the four phylum supposedly to have evolved from Annelids?
Trilobites
Chelicerates
Crustacea
Uniramia
What did insects evolve from?
400/500 Mya insects evolved from myriapod ancestor
Why are springtails debatable as to wither they are insects or not?
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
Defining characteristics of an insect?
Exoskeletons Body plan is head, 3 segmented thorax, 11 segmented abdomen Complete respiratory (tracheal) system with spiracles on body
When did wings appear in the fossil record in insects?
380mya
What reasons do humans have to use insects?
Food for species at other tropic levels De composers Pest control agents Pollinators Producers of products we use (silk, honey) Forensics
Why are insects important in regards to disease?
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
Why are insects important in terms of food production?
Rising human population sees an increase in demand for food
Pest species cause around a 20-30% loss of potential production of food
What is a pest?
Any organism that constrains health, food production or cash generation
What are the four reasons that a pest outbreak may occur?
Geographical movement Agricultural development (mono cultures) Plant breeding/ cultivar selection Destruction of natural regulatory mechanisms
Why does geographical movement increase pest outbreaks?
Absence of natural enemies
Examples include Russian wheat aphid and Mediterranean fruit fly
Why has agricultural development effected pest outbreaks?
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
Why is plant breeding an issue in pest outbreaks?
Reductions in secondary plant substance to increase palatability and improvements in size of harvested plants
Why has destruction of natural regulators affected pest outbreaks?
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
Examples of mid 20th century chemical insecticides
DDT Schradan Allethrin Carbaryl Imadacloprid
What are resurgent and secondary pests?
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
What are the four reasons to study insects?
Numbers
Use to humankind
Disease
Food production
