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Announcements Parasitoid attack on aphids • Exam 3- submit corrections to me • Deadlines – Lab Quiz Monday May 12 – Insect collection May 14 – Field Journal May 12 Insects as endoparasites Order Stresiptera Strepsiptera photos • Few hundred exclusively parasitic species • Feed mostly on hemiptera and hymenoptera • Can switch or sterilize hosts Insect Defenses Insect Defenses • Crypsis – Camouflage – Masquerade – Self • Startle Display • Mechanical • Chemical 1 Crypsis: Camouflage Midwestern grasshopper • Insect resembles background • Can avoid predation and/or aid in prey capture Crypsis: Masquerade Leaf mimic katydid Insect resembles object that is of no interest to predator. Dead leaf mimic Startle Display- cryptic prey suddenly reveals eye shaped structures 2 Eye spots on wings Mechanical Defense Mechanical Defense • Spiny or hard body • Retreats (e.g. caddis fly) • Limb shedding (crane fly, cricket) Chemical defense • Effect – Immediate acting – Delayed- blistering or vomiting • Life stage: egg, larva, pupa • Delivery – In body – Urticating hairs or spines – External secretion glands • Sources – Made themselves (autogeneous) – Derived from food (sequestered) Bombadier beetle defense Bombadier beetle in action 3 Costs of eating distasteful prey Chemical defense • Effect – Immediate acting – Delayed- blistering or vomiting • Life stage: egg, larva, pupa • Delivery – In body – Urticating hairs or spines – External secretion glands • Sources – Made themselves (autogeneous) – Derived from food (sequestered) Delivering chemical defense Larvae display a defensive secretion from glands on the thorax and abdomen Individuals Aggregations Insect Defenses Aposematic coloration in chemically defended insects • Crypsis – Camouflage – Masquerade – Self • Startle Display • Mechanical • Chemical 4 Aposematic coloration Aposematic coloration does not always work • Conspicuous coloration that ‘advertises’ chemical defense • Most effective against visually oriented predators – predators that can remember – typically yellow and red Mimicry Batesian mimicry • Components – Model = individual with chemical defense and warning coloration – Observer = predator that can detect warning colors and remember a bad experience – Mimic = individual that resembles model (closely enough to fool observer) • Types – Batesian • Mimic does not possess defense • Reduces benefit of warning coloration – Müllerian • Mimic possesses defense • Enhances benefit of coloration http://www.bombus.freeserve.co.uk/mimicry.htm Moth mimic Beetle mimic Model wasp Fly mimic Mimicry: Batesian 5 Mimicry: Mullerian Mullerian mimicry in tropical Heliconius Self Mimicry 6
