2. Pests, Plagues & Politics Lecture 1 The Success of Insects

3. Key Points: The Success of Insects Evidence of Success –Numbers –Longevity –Diversity Evidence of Success –Numbers –Longevity –Diversity Reasons for Success –Physical size –Flight –Fecundity Reasons for Success –Physical size –Flight –Fecundity

4. Insects by most measures, are the single MOST successful animal group in the entire evolutionary history of the earth!!

5. Evidence of Insect Success The numbers Number of species: –1,000,000 named –5/6 th of all known animal species Number of living [extant] individuals:extant –10 18 {one million billion} –10 15 ants!!! Biomass: birds = 1 lb per acre humans = 14 lbs per acre insects = one ton per acre {tropics} FYI

6. Evidence of Insect Success Longevity as a taxontaxon Mammals: 200 mya Primates: 70 mya Genus Homo: 2 mya H. sapiens sapiens: 40,000 years ago Insects first appeared 400 million years ago (before dinosaurs!) FYI

8. Evidence of Insect Success Ecological Diversity Insects are everywhere! -Terrestrial, fresh water & marine -Only polar ice caps without insects Latitude –butterflies at 80° North (within the Arctic Circle) –mosquitoes at 70° North –midges at 65° South (Antarctica) Altitude –Hemiptera @ 16,500 feet –Orthoptera @ 16,000 feet –Lepidoptera @ 15,000 feet –Hymenoptera @ 12,000 feet FYI

9. Temperature Majority of insects are stenothermic & ectothermic (not always) stenothermic ectothermic 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 Success Ecological Diversity

10. Insects are small (relative to humans) Reasons for Insect Success Physical Size Average Insect = the housefly –(Musca domestica) –5-7mm

11. Insects are small (relative to humans) Reasons for Insect Success Physical Size Extremes : Smallest = 1/5 th of a mm (1/100 th of an inch) Family: Mymaridae, Fairyfly (a tiny wasp!) next to a match stick. Fairyfly next to a paramecium and an amoeba FYI

12. Extremes : Largest = 6 in.Largest Wingspan = 12 in. Reasons for Insect Success Physical Size Dynastes hercules Rhinoceros beetle Dynastes hercules Thysania agrippina Brazilian moth Thysania agrippina

13. Meganeura Extinct dragonfly (300 mya) with a wingspan of 24 inches!

14. Extremes : Longest = 22 in.Heaviest= 100 g or ¼ lb. (weight of small bird!) Reasons for Insect Success Physical Size Chan’s Megastick Phobaeticus chani Goliath Beetle Fornasinius Fornasini

15. 1) Less food to reach maturity –honey bee: egg to adult in 21 days on 300 mg of food (1/80 th of an ounce) 2) Utilize small retreats to escape/avoid predators 3) Able to utilize a “small” food resource –an egg of another insect, for example!! Reasons for Insect Success Advantages of being small

16. Damage caused by the larva of a leaf-mining insect. [the bug is INSIDE the leaf!] FYI

17. Most, but not all insects are capable of flight APTEROUS (without flight) - Primitive groups that never had wings - Collembola - Silverfish PTERYGOTA = winged (most living insects) - Some Pterygota secondarily lost their wings i.e., Fleas Reasons for Insect Success Flight

18. Insects were the first animals to fly –as long ago as 330 mya –100 million years before birds & mammals ADVANTAGES of Flight 1) Food Capture 2) Escape from Predators 3) Dispersal to new environments 4) SEX Reasons for Insect Success Flight

19. Wing Beat - butterflies8-12 b/s –locust & grasshoppers 18-20 b/s –dragonflies 20-30 b/s [humming birds 30-50 b/s] –honey bee190 b/s –mosquitoes600 b/s –a midge >1000 b/s Speed of Flight –honey bee = 15 mph (22 ft/sec) –dragonfly = 35 to 40 mph Reasons for Insect Success Physics of Flight

20. FECUNDITY = fertility = fruitfulness = “r” = intrinsic rate of increase Paradigm of the house fly [Dr. Hodge] one female & one male in April Assume that all progeny live = 1.91 x 10 20 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 Germany Reasons for Insect Success Fecundity

21. Dr. Herrick & his cabbage aphids: 12 generations between March 31 & August 15 = 822 million tons!!! –predators & parasites –finite food supply –weather Reasons for Insect Success Fecundity …Cute, but ridiculous as these examples leave out:

22. –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 Success Fecundity

23. 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 Success Fecundity

24. Key Points: The Success of Insects Evidence of Success –Numbers –Longevity –Diversity Evidence of Success –Numbers –Longevity –Diversity Reasons for Success –Physical size –Flight –Fecundity Reasons for Success –Physical size –Flight –Fecundity

25. Glossary Extant – 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. Back to lecture