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Pests, Plagues & PoliticsLecture 1

The Success of Insects

Key Points:

The Success of InsectsEvidence of SuccessNumbersLongevityDiversity

Reasons for SuccessPhysical sizeFlightFecundity

Insects by most measures, are the single MOST successful animal group in the entire evolutionary history of the earth!!Evidence of Insect SuccessThe numbersNumber of species:1,000,000 named5/6th of all known animal species

Number of living [extant] individuals:1018 {one million billion}1015 ants!!!Biomass:birds = 1 lb per acrehumans = 14 lbs per acreinsects = one ton per acre {tropics}

FYI

Evidence of Insect SuccessLongevity as a taxonMammals: 200 myaPrimates: 70 myaGenus Homo: 2 myaH. sapiens sapiens: 40,000 years agoInsects first appeared 400 million years ago(before dinosaurs!)FYI5

Evidence of Insect SuccessEcological DiversityInsects are everywhere!Terrestrial, fresh water & marineOnly polar ice caps without insectsLatitudebutterflies at 80 North (within the Arctic Circle)mosquitoes at 70 Northmidges at 65 South (Antarctica)AltitudeHemiptera @ 16,500 feetOrthoptera @ 16,000 feetLepidoptera @ 15,000 feetHymenoptera @ 12,000 feetFYIFYIFYI TemperatureMajority of insects are stenothermic & ectothermic (not always)Cold- Stoneflies & mosquito larvae active @ 0 C- Midge larvae recovered from immersion in liquid nitrogen (-190 C)Heat- Hot springs at Yellowstone with midge larvae active at 49-51 C Evidence of Insect SuccessEcological Diversity

Insects are small (relative to humans)Reasons for Insect SuccessPhysical SizeAverage Insect = the housefly(Musca domestica)5-7mm

Insects are small (relative to humans)Reasons for Insect SuccessPhysical SizeExtremes:Smallest = 1/5th of a mm (1/100th of an inch)

Family: Mymaridae, Fairyfly (a tiny wasp!) next to a match stick.

Fairyfly next to a paramecium and an amoebaFYIExtremes:Largest = 6 in.Largest Wingspan = 12 in.Reasons for Insect SuccessPhysical Size

Rhinoceros beetle Dynastes hercules Brazilian moth Thysania agrippina

Meganeura

Extinct dragonfly (300 mya) with a wingspan of 24 inches!Extremes:Longest = 22 in.Heaviest= 100 g or lb.(weight of small bird!)

Reasons for Insect SuccessPhysical SizeChans Megastick Phobaeticus chaniGoliath Beetle Fornasinius Fornasini

1) Less food to reach maturityhoney bee: egg to adult in 21 days on 300 mg of food (1/80th of an ounce)

2) Utilize small retreats to escape/avoid predators

3) Able to utilize a small food resourcean egg of another insect, for example!!Reasons for Insect SuccessAdvantages of being smallDamage caused by the larva of a leaf-mining insect.[the bug is INSIDE the leaf!]

FYIMost, but not all insects are capable of flight

APTEROUS (without flight)- Primitive groups that never had wings- Collembola - SilverfishPTERYGOTA = winged (most living insects)- Some Pterygota secondarily lost their wingsi.e., FleasReasons for Insect SuccessFlightInsects were the first animals to flyas long ago as 330 mya100 million years before birds & mammals

ADVANTAGES of Flight1) Food Capture2) Escape from Predators3) Dispersal to new environments4) SEXReasons for Insect SuccessFlightWing Beat- butterflies8-12 b/slocust & grasshoppers 18-20 b/sdragonflies 20-30 b/s [humming birds 30-50 b/s]honey bee190 b/smosquitoes600 b/sa midge >1000 b/s

Speed of Flighthoney bee = 15 mph (22 ft/sec)dragonfly = 35 to 40 mphReasons for Insect SuccessPhysics of Flight

FECUNDITY = fertility = fruitfulness = r = intrinsic rate of increase

Paradigm of the house fly [Dr. Hodge]one female & one male in AprilAssume that all progeny live= 1.91 x 1020 flies by August!!!= enough flies to cover the earth with a layer of flies 47 feet thick!!!!

Wrong says Dr. Oldroy, only an area the size of GermanyReasons for Insect SuccessFecundityDr. Herrick & his cabbage aphids:12 generations between March 31 & August 15 =822 million tons!!!

predators & parasitesfinite food supplyweatherReasons for Insect SuccessFecundity

Cute, but ridiculous as these examples leave out:The average r value for an insect is 100 to 150 fertilized eggs in her life time.Not so bad relative to humans, with the average female producing 400 eggs of which 2.2 will be fertilized.Reasons for Insect SuccessFecundity

High Fecundity + a short life span + a short generation time =

A group of organisms more responsive to short-term environmental change (selective pressures) = A group with pronounced evolutionary success!!Reasons for Insect SuccessFecundityKey Points:

The Success of InsectsEvidence of SuccessNumbersLongevityDiversity

Reasons for SuccessPhysical sizeFlightFecundity

GlossaryExtant adj. Still in existence; surviving.Taxon - noun, plural: taxa (taxonomy) (1) Any group or rank in a biological classification into which related organisms are classified. (2) A taxonomic unit in the biological system of classification of organisms, for example: a phylum, order, family, genus, or species. Stenothermic - adj. Capable of living or growing only within a limited range of temperature.Ectothermic - adj. Of or relating to an organism that regulates its body temperature by exchanging heat with its surroundings; cold-blooded.

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