Unit 4 in Entomology
Unit 4 Integument, Development and Reproduction.
Have you ever watched a butterfly emerge from its cocoon?
How does it go from being a little worm like
caterpillar in to a beautiful butterfly with scaled wings and a different type of mouth part and different
Well, if you've ever watched this amazing process, you may have wondered how it happens.
this unit you will study the molting process, including all of the hormones involved.
First, you'll need to
learn about some of the structures and the composition of the exoskeleton.
In the final portion of this
unit, you learned about the insect reproductive system and how insects propagate their kind.
There are five objectives in this unit, by the end of this unit you should be able to: describe the layers of
the integument, tell me why tell me why having an exoskeleton would be advantageous and
You should be able to use the proper terms for the structures involved in molting and
explain all the steps in the molting process.
You should explain the role of some of the chemicals,
juvenile hormone and ecdysone, tell me where they come from and how they're used together during
Should also, be able to identify the internal and external reproductive structures of insects and
describe what they do or what they're used for.
In unit one, you learned that arthropods have an outer exoskeleton made up of chitin and proteins.
it’s a little more complex than that.
The exoskeleton is also called the cuticle and is made up of three
distinct layers: the epicuticle, exocuticle and endocuticle.
The top layer is extremely thin, it's the
epicuticle, and it's the protective waterproof layer made up of fats and polyphenols.
The exocuticle is the
hardened layer, it consists of a chitin-protein matrix made of microfibers linked together that forms like a
plastic kind of material.
The innermost layer of the cuticle is flexible, it's the endocuticle.
It's also made
of chitins and protein but they're not linked together to form a hard layer, it remains flexible.
is only made of chitin and proteins, it's not made up of cellular material.
Directly below the cuticle is the
cellular layer called the epidermis.
The epidermis is very important because those cells are the source of
the proteins, chitins, lipids, and all the other products contained in the exoskeleton in other words, the
epidermal layer, the cellular layer supplies all the materials needed for the Endo, exo, and epicuticle.
When an insect molts these cells play a critical role, because they have to replace all of those ingredients
needed to form the exoskeleton.
The cuticle and epidermis make up what we call the insect's integument.
Below the integument is a
Scientists aren't really clear what makes up this layer but we do know that this
layer separates the epidermal cells from the insect's blood, the hemolymph.
The membrane has pores
large enough to allow proteins and other molecules in the blood to pass through the membrane and on to