2. Arthropod Defenses a Glimpse at

3. Some Chemical Defenses Types Class I: cause some direct harm to predator. E.g. toxic venom, caustic liquid, explosive gas, etc. (often accompanied by aposematic coloration) Class II: discourage feeding. E.g. toxic haemolymph, noxious odors Sources (Where do they come from?) –Host plants, prey, mother Deployment (At what stage are they used?) –Egg, larva or nymph, pupa, adult Application (How are they used?) –Bite, sting, squirted, oozed, gassed, passive-internal

4. Aposematically colored bugs. Aposemitism: self-advertising, usually through color, that an organism is poisonous or can harm a predator in a way that benefits the survival of the bearer. The effect may be long-lived if the predator learns avoidance, thus protecting other prey. Aposematic colors are usually some combination of red, yellow, & black. Aposemitism may also be involved in mimicry complexes.

5. A caterpillar with urticating hairs advertised with aposematism.

6. Many darkling beetles and stinkbugs emit foul-smelling quinone-laden gas.

7. Cinnabar moth larvae, exotic biocontrol agents of tansy ragwort, sequester toxic chemicals from the plant for their own defense.

8. Gullen & Cranston 2005 Bombardier beetles (Brachinus spp.) shoot an explosive noxious blast when disturbed. (Hydrogen peroxide + hydroquinones from secretory tissue) + enzymes from wall of reservoir => valve release => explosion in reaction chamber. Near- boiling hot gas is ejected with an audible “pop”. Text box 14.3

9. Gullen & Cranston 2005 Role of cantharadin in certain pyrochroid beetles. (Neopyrochroa flabellata). Text box 14.4 Defensive chemical in prey protects eggs of next generation. Environmental acquisition + horizontal transmission + vertical transmission of an multi-function defensive toxin (cantharidin). Male: defensive protectant aphrodesiac Female: defensive protectant nuptial gift Egg: defensive protectant PATH OF TOXIN: Environment (prey?) => male => courtship/nuptial gift => selection by female => female acquisition through mating => transfer to eggs => egg protection.

10. “harmful” models “harmless” mimics

11. Types of Defense Against Physical Forces  Threats  Dehydration, Drowning, Freezing, Radiation, Wind (blowing away) Against Biological Forces  Threats  Microbes  Parasites  Predators  Strategies  Passive  Active Important Points Virtually all arthropods have adaptations for defense. Certain adaptations may be both defensive and serve some other function, e. g. flatness of fleas. Apparent defensive adaptations against humans per se are incidental.

12. Insect Defence Against Biological Enemies Disappearing, (Out of Sight - Out of Mind) hiding, dropping running, hopping, flying Costumes: crypsis & camouflage mimesis

13. Passive Resistance, Discouraging the Attacker Chemical toxic haemolymph secretion of noxious compounds urticating hairs Morphological tough, slippery, spiny cuticle autotomy (part behavioral) removable scales, hairs “backwards” appearance Behavioral feigning death Scare Tactics (Morphological/Behavioral) eyespots aposemitism

14. Active Resistance, Resisting attack or Fighting Back Educatively Injuring the Attacker slow-acting toxins bites & stings Killing the attacker Collective Strategies, Special Adaptations of Social Species confusion effects nest blocking mass counter-attack bluff attack

15. Visual Defenses (Physical Appearance) Mimicry  True Mimicry Batesian Mullerian  Mimesis & Startle Effect Crypsis Warning coloration

29. Some Morphological/ Mechanical Defenses Tough or Slippery Exoskeleton Odd shape Special structures –Spines (passive or active poking) –Claws (for hanging on to substrate) –Scales (slippery) –Expendable Wing Surface (detachable) –Jumping legs or other springy devices (escape) –Stings (behavioral)

39. Defense?

40. Advanced necrosis from brown recluse spider bite. Not the primary function of the defensive adaptation (venom).

41. Behavioral Strategies Passive –Hiding - often with Mimicry, Mimesis, Crypsis –Timing of Development –Migration & Diapause –Autotomy Active –Aggressive defense (entails one or more special weapons) –Escape –Startle –Death-feigning

47. Special Defense Strategies of Gregarious & Social species (most are mixed strategies) Protective Nest Large Numbers => startle/confusion effect Massive counter-attack, e.g. stinging Sophisticated “alarm/attack” signaling Soldier caste (specialized for defense)

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