11 Insect Metamorphosis

Dr. PARVISH PANDYA’s presentation

“Metamorphosis inInsects”

A presentation compiled from various sources by

Dr. PARVISH PANDYA,Zoology Dept. Bhavan’s College, Andheri.


Sites from which presentations have been downloaded and later editted. I am indeed thankful to them for their kindness and support :http://esg-www.mit.edu:8001/esgbio/cb/org/organelles.htmlhttp://faculty.pnc.edu/jcamp/parasit/parasit.htmlhttp://www.amnh.org/rose/hope/creatinghope/http://www.biology.eku.edu/SCHUSTER/bio%20141/POWERPOINT%20NOTES/Intro%20to%20Protozoa_files/fullscreen.htmhttp://www.biosci.ohio-state.edu/~zoology/eeob405/http://www.tulane.edu/~wiser/protozoology/pwpt/http://www.iep.water.ca.gov/suisun/photos/wildlife.htmlhttp://www.uta.edu/biology/marshall/2343/http://www.uta.edu/biology/faculty/faculty.htmlhttp://www.okc.cc.ok.us/biologylabs/Documents/Zoology/PowerPoint.htmhttp://bio.fsu.edu/http://www.aw-bc.com/http://www.nhm.org/http://www.geo.cornell.edu/eas/education/course/descr/EAS302/presentations/

It is very easy to find mistakes in these presentations…..I request you to kindly rectify them and supply me the modifications needed at [email protected] a lot and have fun in teaching & learning Zoology….

http://esg-www.mit.edu:8001/esgbio/cb/org/organelles.html

http://esg-www.mit.edu:8001/esgbio/cb/org/organelles.html

http://faculty.pnc.edu/jcamp/parasit/parasit.html

http://www.amnh.org/rose/hope/creatinghope/

http://www.biosci.ohio-state.edu/~zoology/eeob405/

http://www.tulane.edu/~wiser/protozoology/pwpt/

http://www.iep.water.ca.gov/suisun/photos/wildlife.html

http://www.uta.edu/biology/marshall/2343/

http://www.uta.edu/biology/faculty/faculty.html

http://www.okc.cc.ok.us/biologylabs/Documents/Zoology/PowerPoint.htm

http://bio.fsu.edu/

http://www.aw-bc.com/

http://www.nhm.org/

http://www.geo.cornell.edu/eas/education/course/descr/EAS302/presentations/

mailto:[email protected]


Insect metamorphosis

“change in form”


Entomological Terms

Stadium: period of time between successive molts

Instar: the insect itself between two successive molts

Stage: principal divisions in life cycle (egg, larva, nymph, pupa, adult)

Example: The first instar (first larval stage) lives in wood.


Simple Metamorphosis1. Ametabolous (“no”)

wingless as adults; silverfish, collembola

2. Hemimetabolous (“incomplete”)aquatic nymphs that do not resemble adults; mayflies, dragonflies, etc.

3. Paurometabolous (“gradual”)nymphs and adults live in same habitat; proportions differ; bugs


Metamorphosis

LarvaeYoung very different from adults

Holometabolous

Nymphs (land)Naiads (water)

Specific number of molts

Paurometabolous

instarslarvae look like adults, just smaller

Ametabolous

Young calledAppearanceType

Dr. PARVISH PANDYA’s presentationAmetabolous Incomplete Complete


“Simple”

“Complete”


Metamorphosis• ancestral condition – ametamorhic• continue molting after sexual maturation• indeterminate no. molts

Thysanura


Hemimetabolous Development• “incomplete” metamorphosis• final molt - wings and genitalia• some with non-feeding reproductive stages

Incomplete metamorphosisIn mayfly


Review Metamorphosis


Complete Metamorphosis

(Holometabolous)Wings develop internally.egg, larvae, pupa, adultbeetles, butterflies, fleas, flies, bees, etc.


B is for Butterfly

Though the butterfly hasn’t a notionOf how to accomplish eclosionIt always takes placeWith exquisite grace,Gymnastics, and later, slow motion


Holometabolous Development• resting stage between larval instars and adult• the ultimate innovation why so successful?• hypothesis: multiple niche exploitation• relative stage-specific selection• non-feeding reproductive stages

pupa


Pupation• larval tissues are partly - entirely destroyed• replaced by growth of imaginal disks


a-Ecdysone

Corpus alatum

Prothoracicgland

Juvenilehormone

Tobaccohornworm


See Elzinga, p. 133


Commercial silkworm, Bombyx mori

Normal Development

Corpora allataremoved(less JH)

Dwarf pupaand adult

Corporaallataremoved(less JH)

Very smallpupa and adult

Corpora allata

implant (more JH)

Giants

6


Hypermetamorphosis

• Occurs in parasitic insects where firstinstar seeks out the host, and once in the host, molts into a less active larva.

• Examples: Coleoptera: MeloidaeColeoptera: Rhipiphoridae

Strepsiptera (twisted-wing parasites)A few Diptera and Hymenoptera


Intermediate Types of Metamorphosis

A. Thrips: larva, prepupa, pupa, adult

B. Whiteflies: 1 instar (active and wingless), 2-3 instars (sessile and scale-like), 4 instar, adult

C. Male scale insects: 1 instar (crawler), subsequent instars, pupa, adult (winged)


Hypothesis: larval stage (holometaboly) resulted from altered hormonal control of embryogenesisTrumen and Riddleford ’99. Nature 401: 447-452• Ecdysteroids and Juvenile Hormones• obs. JH absent during embryo formation in ametabolous and hemimetabolous insects• -> developing embryo resembles adult• holometabolous insects: early appearance of JH suppresses some adult-directed growth


Blattodea

Diptera

MantodeaIsoptera

PsocopteraPthirapteraHemiptera

Thysanoptera

Plecoptera

Orthoptera

Dermaptera

Phasmida

Odonata

Ephemeroptera

Thysanura

323 mya290245

20814665

1.64oldest fossil

Paleoptera

Apterygota

Neoptera

hemimetabolous

ametabolous

holometabolous

Strepsiptera

NeuropteraRaphidiopteraMegalopteraColeoptera

Mecoptera

Siphonaptera

Trichoptera

Lepidoptera

Hymenoptera

11 Insect Metamorphosis

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