EXCRETORY SYSTEM OF INSECTS

• For the efficient maintenance of water and the ionic balance in the hemolymph, the waste products of the metabolism are to be removed or eliminated. These waste materials may be in solid, semisolid, liquid, or gaseous form.
• The principal excretory product in gaseous form is CO2, the liquid form is honeydew, the solid form is Urea/uric acid, and the semi-solid form is allantoin.

The organs that are involved in the process of excretion are:

1. Malpighian tubules

2. Integument or body wall

3. Tracheal system

4. Alimentary canal

5. Nephrocytes

1. Malpighian tubules:

• The Malpighian tubules are long, tubular structures that open proximally in between the midgut and hindgut and close distally, floating freely in the hemolymph
• Malpighian tubules are absent in aphids and Collembola.

Functions of Malpighian tubules:

a)Helps in the process of excretion or removal of waste products.

b)Regulate the internal body environment by maintaining ionic and water balance

c)In the case of glow worms, the distal ends of tubules produce light energy.

d) Also helps in the storage of Ca necessary for processes such as hardening of puparium.

2. Integument:

• In some insects, where respiration occurs through the body wall, CO2 is removed through integument as a waste product (cutaneous respiration).

3. Tracheal system:

• Function in the elimination of CO2 through spiracles.

4. Alimentary canal :

• Removes the unwanted material, dead cells formed during enzyme secretion (holocrine), and intima layer during molting.

5. Nephrocytes:

• Nephrocytes are cells that take up foreign chemicals of relatively high molecular weight which Malpighian tubules may be incapable of dealing with.
• Nephrocytes help in the removal of ammonia, chlorides, dyes, colloidal particles e,tc.