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Insect colouration and its importance in entomology
- 1. Colouration & Importance of colouration in Insects
- 2. What is colour ? How colour production takes place in insects ? 1)Physical or structural colours 2) Pigmentary colours Significance of colour in insects a) Predation avoidance b) Intraspecific recognition
- 3. Colourational Defense • I am some one else Warning colouration • I am not tasty • I am dangerous • I am not here Cryptic colouration Revealing colouration Mimicry
- 4. 1. Crypsis Colouration that makes against their background animals difficult to distinguish Crypsis works only if the animal is resting on the appropriate background and usually only when the animal is not moving Homotypism Homomorphism Homochromism
- 5. Homochromism • Similarity of animals to the colour of inanimate objects • These insects are often the same colour as the leaves or twigs on which they rest
- 6. Homomorphism Similarity of animals to the form of inanimate objects These insects are often the same form as the leaves or twigs on which they rest
- 7. Homotypism • Similarity of animals to the colour & form of inanimate objects • Same colour & form as the leaves or twigs on which they rest The South Indian Blue Oakleaf Kallima horsfieldii, Nymphalidae Stick insect Phasmida
- 8. 2. Revealing Colouration Deimatic behavior Any pattern of threatening or startling behavior such as, suddenly displaying conspicuous eye spots - to scare off or momentarily distract a predator thus giving the prey animal an opportunity to escape
- 9. Deimatic Behaviour • Dynamic, frightening or startle behavior • Display of some conspicuous colour or structure • Static display • Deep red or black hind wing • Praying mantids & Phasmids • Phymateus sp, Smerinthus ocellatus, Aglais io
- 11. 3. Warning Colouration Aposematism The correlation between conspicuous signals, such as bright colouration & prey unprofitability Candy Rowe, 2001
- 12. Pseudosphinx hawk moth caterpillar Brightly Coloured Species – Puzzle for Biologist Henry Walter Sexual selection 1866 Historic approach 1862
- 15. Aposematic insects Reference - The insects structure & function (2011): R. F. Chapman Species Stage Colour Basis of unpalatability Zonocerus variegatus Adult B/Y & R markings Various chemicals Romalea guttata Adult B/R hind wings Various chemicals Aphis nerii All Bright yellow Cardiac glycosides Oncopeltus fasciatus Adult Y/B spots Cardiac glycosides Coccinella septemfasciata Adult R/B spots Alkaloids Hycleus lugens Adult Yellow spots Alkaloids Vespula vulgaris Adult Y/B stripes Sting Tyria jacobaeae Larva B/Y stripes Pyrrolizidine alkaloids Tyria jacobaeae Adult B/R marks Pyrrolizidine alkaloids Danaus plexippus Larva W/B & Y stripes Cardiac glycosides Zygaena filipendula Adult B/R spots Cyanogenic glycosides
- 16. Orthoptera Zonocerus variegatus Reference - The insects structure & function (2011): R. F. Chapman Romalea guttata
- 17. Coleoptera Hycleus lugens Reference - The insects structure & function (2011): R. F. Chapman Coccinella septemfasciata
- 18. Hymenoptera Vespula vulgaris Reference - The insects structure & function (2011): R. F. Chapman
- 19. Larval Lepidoptera Tyria jacobaeae Reference - The insects structure & function (2011): R. F. Chapman Danaus plexippus
- 20. Lepidopteran adult Tyria jacobaeae Reference - The insects structure & function (2011): R. F. Chapman Zygaena filipendula
- 21. 4. Mimicry • Resemblance of one species to another • I am someone else • Related to Camouflage Defensive Aggressive Auto/Self
- 22. Defensive/ Protective mimicry • It takes place when organisms are able to avoid an encounter that would be harmful to them by deceiving an enemy into treating them as something else Batesian mimicry Mullerian mimicry Martensian/ Emsleyan mimcry Wasmannian mimicry
- 23. Batesian mimicry • A harmless mimic poses as harmful A sheep in wolf ’s clothing • Also known as Parasitic mimicry • Mimic - emits signals similar to model but does not possess the attributes that makes it unprofitable to predators Henry Walter Bates
- 25. Mullerian mimicry • Two harmful species share similar perceived characteristics • Mutualistic mimicry or Convergence • Predation on any one species is reduced • When two poisonous species have similar markings; fewer insects need to be sacrificed in order to teach the predators not to eat these unpalatable animals Fritz Muller
- 27. Wasmannian mimicry • The mimic resembles a model along with which it lives as an inquiline in a nest or colony • Most of the models here are social insects such as ants, termites, bees & wasps Erich Wasmann Araeoschizus sp Reichenbachia spatulifer
- 28. Mertensian/ Emsleyan mimicry • Named after M. G. Emsley & German herpetologist Robert Mertens • A deadly mimic resembles a less harmful but lesson- teaching model Robert Mertens
- 29. Aggressive mimicry • Also known as Peckhamian Elizabeth Peckham mimicry after George & • Predators or parasites which share characteristics with a species harmless to their prey, allowing them to avoid detection by the latter • Mimic may resemble the prey or host itself • The model may be affected –vely, +vely or neutral
- 31. Automimicry/ Interspecific mimicry • The species relationship between model & mimic • Occurs within a single species one case being where one part of an organism’s body resembles another part • Mimic imitates other morphs within the same species • Deflection marks in Lycaneid butterfly
- 32. Deflection marks Deflection marks are those which divert the attack of a predator away from the most vulnerable part of an animal to where it will do minimal damage
- 33. Polycephalic Butterflies Arawacus aetolus Cycnus phaleros Rekoa palegon Atlides atys Calycopis isobeon
- 34. Intraspecific detection • Found in dragon flies, damsel flies and butterflies a) Recognition of females b) Recognition of conspecific males Dragon flies ex. Plathemis males – defend territory, dorsal side of abdomen blue. If other males enter –native males lift abdomen and dsiplay colour – avoid intruding males.
- 35. References Chapman, R. F . (2011). Visual signals: Colour and light production. The insects structure & function (4th edition), pp. 657-679. Robert K. Robbins, The American Naturalist. The Dz F alse Head dz Hypothesis: Predation and Wing Pattern Variation of Lycaenid Butterflies. Vol. 118, No. 5 (Nov., 1981), pp. 770-775