Insect Molting and Metamorphosis

7 Molting Stages

1} Intermolt

Insects not molting

2} Apolysis

Epidermis detaches from endocuticle

Epidermis secretes molting gel in between

3} Mitosis

Epidermal cells divide/become columnar

Epidermis > Culicullin Later

Gel > Active Fluid > Cuticle Degradation

4} Digestion

Fluid enzymes digest old endocuticle

5} New cuticle formation

Formed from Epidermis

Fluid and Culiculin remains

6} Reabsorption

Fluid reabsorbed into mouth/anus

Haemolymph pumped into ecodysol sutures to weakne/open cuticle for shedding

7} Ecdysis

Old cuticle breaks, epidermise/layers expand

Wax/Cement layer deposited via epidermal pores

Determining Steps of Growth

Mitosis of epidermis

Expansion during ecdysis

Regulation of Molting

PTTH (brain) > Prothoracic glands to secret Ecdysone

Corpora Allata secretes JH

PTTH

Trigger for molting. Secreted by growth indicator

Reinjection of brain (Brain secretion)= Molting (Moth, Kopec)

Exp (L > P)

Remove brain, reinject brain, blood tight ligation

Ecdysone

Parabiosis: Sharing of haemolymph = molting

Exp (N>A)

Blood + decapitation, Same but 3 day wait, Parabiosis

Prothoracic Glands

Also needed for molting

Exp P>A

Butterfly

Chilled pupa > RT > brain out (no) > reinject (molt)

Warm pupa > chill brain (molt)

Obligatory Diapause

~ Hybernation

JH (via Corpora Allata)

Retention of juvenille state

Exp N>A

Kissing Bugs

Parabiosis 5th/4th instar

Result: 6th/5th instar

Expected: Adult/5th