INSECT DEFENSE MECHANISM

K.Elango,
Ph.D Scholar(Agrl.Entomology)
Tamil Nadu Agricultural University,
Coimbatore-641003
Mobile number : [phone]
[phone]

1. Welcome… ENT 803 - ADVANCED INSECT PHYSIOLOGY (2+1) COURSE TEACHER : Dr. S. Manimegalai Ph.D., 1

2. 4000 species /year 100 species /day 1 species every 15 minutes Insects live in a dangerous world!!! www.iucn.org 2

3. DEFENSE “ To make or keep safe from danger, attack, or harm” - Sigmund Freud (1894) 3

4. Enemies for insects Birds Amphibians Mammals Other Arthropods Great Humans 4

5. Are u ready to eat ? 5

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7. INSECTS DEFENSE MECHANISMS By ELANGO.K 7

8. “ All insects are potential prey or hosts to many kinds of predators, parasitoids, or less often, parasites ” Insectivores : Organisms that rely almost exclusively on a diet of insects. Parasite : Organisms that live at the expense of another organism but do not kill it. Parasitoid : A parasite that ultimately kills its host. 8

9. Protective Constructions 9

10. - Eggs and egg masses covered by hairs - Ootheca or protective coverings - Stalked eggs gain protection from predators Egg stage Cutworm egg mass Green lacewing fly Eggs Ootheca 10

11. - Physical protection against parasitoid oviposition can be provided by the integument . - Cuticular appendages like scales and spines . - Portable cases made out of plant materials along which they move, feed and finally pupate inside the cases. Larval stage Thick cuticle Scoli Protected case 11

12. Pupal cocoons can also provide protection - One ichneumonoid species requires nearly an hour to penetrate the cocoon. Silk, frass, body hair, soil - used for forming protective cocoons. Mosquito pupa is unusually active thereby it escapes from aquatic predators. Pupal stage 12

13. A combination of mobility and heavy sclerotization makes adult insects especially difficult targets. Mealy bugs, waxy thread covering the body afford protection . Hard shell covering protects the soft bodied insects. Adult stage 13

14. Types of Insect Defenses 1.Primary defense 2.Secondary defense 3.Tertiary defense 14

15. Primary Defense Defense that reduces the probability of encounter by natural enemy - Camouflage - Mimesis - Mimicry Crypsis – Visual deception to avoid predator encounters 15

16. Homochromism: Colour is similar – Preying mantis Homomorphism: Form is similar- Cow bug Homotypism : Both colour and form are similar –Leaf insect Cryptic defense 16

17. Camouflage - Camouflage : Resembling the general background 17 Geometer moth Brimstone butterfly Grass hopper

18. - Mimesis : Resembling an object that is a particular feature of the environment, and is uninteresting to the predator. Mimesis 18

19. Similarity of one species to another which protects one or both It is a situation in which one species called the mimic resembles in colour, form, and/or behaviour another species called the model . This similarity can be in appearance, behaviour, sound, scent and even location with the mimics found in similar places to their models. Mimicry 19

20. 1.Batesian mimicry : “ False advertising " - Henry Walter Bates, 1861 - Edible species look like distasteful one - The mimic shares signals similar to the model & gets protection Types of Mimicry Monarch Butterfly Viceroy Butterfly Model Mimic 20

21. 2. Mullerian mimicry - Fritz Muller in 1879, - Both mimic and model - unpalatable - Ingestion of either by a predator results in the avoidance of both the species - cardiac glycosides - Advantageous to both mimic & model Types of Mimicry Danaus chrysippus Danaus genetua 21

22. 3 . Wasmannian mimicry - Eric Wasmann in 1970 - Mimic resembles it's host (the model) in order to live within the same nest or structure - Models - social insects such as ants, termites, bees and wasps Types of Mimicry Several jumping spiders closely resemble ants 22

23. 4. Aggressive mimicry / Peckhamian mimicry - Poulton in 1890 - Predators or parasites which share the same characteristics as a harmless species, allowing them to avoid detection by their prey or host. Types of Mimicry 23

24. Crypsis is not an infallible form of protection There is evidence that once birds find a cryptic insect they will learn how to find others like it. 1. American Blue jays - stick mimicking caterpillars 2. Primates can identify a cryptic insect by one pair of unfolded legs 24

25. Morphological defense Behavioral - Individual & Group Mechanical Defenses - Chemical Defenses Seconda ry Defense 25

26. Morphological Defense 26

27. - Some caterpillars have eyespots that make them look like a bigger, more dangerous animal, like a snake. - An eye spot is a circular, eye-like marking found on the body of some caterpillars. - These eyespots make the insect look like the face of a much larger animal and may scare away some predators . Eye spots 27

28. Vertebrate form convergence 28

29. - Some caterpillars are poisonous to predators. These caterpillars get their toxicity from the plants they eat . Generally, the brightly colored larva are poisonous; their color is a reminder to predators about their toxicity. Monarch and the Pipevine Swallowtail . Poisons 29

30. 1. Horny integument - Hard & Highly sclerotised, it can resist break, penetration by insectivores birds - Jewel beetle, rhinoceros beetle. 2. Scerotized cerci - Earwigs 3. Raptorial leg - Preying mantids 4. Tentacles – Danaidae larvae 5. Double vision - Whirligig Beetle Structural Defense 30

31. Double vision 31 Scerotized cerci Raptorial legs Tentacles

32. Behavioural Defense 32

33. Behavioural Defense Jumping: Effective form of escape from enemies. - Reflex dropping: Caterpillars often drop from their food on a strand of silk when disturbed and reel themselves back up when the danger has passed 33

34. Behavioural Defense Thanatosis : Many beetles & weevils feign dead which is a form of defense against a predator which prefers live prey. - Hiding : Some caterpillars encase themselves in a folded leaf or other hiding place. 34

35. Behavioural Defense Cycloalexy : - Forming aggregations in defensive circles. Gregarious and Social Insects: - Chemically defended, aposematic insects tend to cluster rather than spread out in the environment . 35

36. Mechanical Defense 36

37. Mechanical Defense - Wax and powder secretion : Entangles the mouthparts of potential predators Cockroaches have a permanent slimy coat 37

38. Aphids secrete lipids to gum up mouthparts of arthropod predator Many termites secrete chemicals that harden upon contact with air that impair movement of predators Autotomy : - Detachable body structures: Moth scales, Phasmatodea legs, orthoptera legs, and Crane Fly legs Mechanical Defense 38

39. Chemical Defense - Many mechanical defenses are only useful against arthropod predators - Chemicals allow defense against a broad range of predators 39

40. Class I - Chemicals that are noxious because they irritate, hurt, poison, or drug individual predators . Class II – Chemicals that are innocuous but tend to stimulate olfactory or gustatory receptors, basically they smell bad contribute to aposematism . 40

41. 1. Sources - Where do they come from? - Host plants, prey, mother 2. Deployment - At what stage are they used? - Egg, larva or nymph, pupa, adult 3. Application (How are they used?) - Bite, sting, squirted, oozed, gassed, passive-internal 41

42. Immediate Class I -Chemicals Immediate acting chemicals affect the predator as it is handling the potential prey item- prey protected by these chemicals often survive. These chemicals secreted externally - E.g. Buckmoth caterpillars 42

43. Delayed Class I - Chemicals - Chemicals with delayed reactions, such as swelling or vomiting , occur after the prey item has been consumed. - These types of chemicals are found in the hemolymph or other internal tissue of the insect. E.g. Monarch butterflies and caterpillars 43

44. Aposematism in Nocturnal Insects Class I protected insects are generally aposematic - but bright coloration is not effective aposematism at night . Aposematism : Self warning of unpalatability , particularly using color, but sound or light can also be used. Some nocturnal moths emit sounds - Bioluminescence of some coleoptera larvae and lampyridae 44

45. Where do Insects get their defensive chemicals???? 1. Ingestion 2. Synthesis 45

46. Ingestion - Plants synthesize toxins to defend themselves against herbivores . - Some insects are able to overcome these defenses and become “ specialists ” on plants producing those compounds. - These insects often can use these the defensive plant toxins to defend themselves . 46

47. Osmeteria 1. Expelled by eversion of pair of coloured protrusible structures - Releasing a disagreeable odour in response to a defense larvae of certain swallowtail butterflies - eversible glands just behind the head Osmeteria secret Methyl buteric acid- Citrus butterfly . 2. Larva of saw fly Neodiprion sp. Sequester both monoterpenes & sesquiterpenes from their pine host. 47

48. Synthesis - Many insects can synthesize their own defensive chemicals Stink glands – Stink bugs Meloidae Beetles - Cantharidin Buprestidea Beetles – Buprestin Ants ( Formicidae) – Formic acid Bombardier beetles - Quinone 48

49. Defeat Defeat Defeat Before Defeat Defeats You…… T H A N K Y O U …… By ELANGO.K 49