The document outlines the excretory system of insects, detailing various excretory organs such as malpighian tubes, labial glands, and nephrocytes, along with their histology and functions. It explains the process of nitrogen excretion, including the distinction between uricotelism in terrestrial insects and ammonotelism in aquatic insects. Additionally, it covers concepts like cryptonephry and storage excretion, highlighting the roles of different cells in waste elimination and internal regulation.

1. EXCRETORY ORGANS IN
INSECTS

2. SYNOPSIS
1.EXCRETION SYSTEM
2.EXCRETORY ORGANS
3.TYPES OF EXCRETORY ORGANS
 MALPIGHIAN TUBE
 Histology
 Function
 LABIAL GLAND
 NEHROCYTES
 URATE CELLS
 OENOCYTES
 RECTUM/GUT
4.NITROGEN EXCRETION
5.CRYPTONEHRY
6.STORAGE EXCRETION

3. DEFINITION
In living organism and cells the process of eliminating or expelling
waste matter.
It is the passive biological system that remove unnecessary
materials from the body of an organism so as to help maintain
internal chemical homeostasis and prevent damage to the body

5. Internal body organ and group of tissues and cells which perform
excretion known by the excretory organ they are
Kidney (human)
Flame cells (flatworms)
Urinary bladder
In insects the function of excretion is chiefly concerned with the
elimination of several types of substances such as mineral salts and
water and products of the metabolism of nitrogenous substances ,
sulphur and phosphorus certain complex compounds that are produced
incidentally as a result of certain accidents or as a by product in case of
certain chemical changes and the acids and alkalis
It is a process by which the internal environment of the insects is
regulated at a constant level by removing surplus and injurious materials

6. TYPES OF EXCRETORY ORGANS
1.MALPIGHIAN TUBE
2.LABIAL GLAND
3.NEPHROCYTES
4.URATE CELLS
5.OENOCYTES
6.RECTUM AND GUT

7. THE MALPIGHIAN TUBE
The main organ of excretion and osmoregulation in insects are
the malpighian tubules .acting in association with rectum or
ileum
ORIGIN = they are outgrowth of the alimentary canal and consist of
long thin tubules
STRUCTURE = they are long, slender, blind tubules which are
often convoluted
NUMBERS = varies from group to group
Anoplura – 4
Thysanoptera , hemiptera , diptera, siphonoptera – 4 to 6
Psocoptera and coleoptera – 2 to 8
Isoptera and lepidoptera ,trichoptera – 6
Odonata-50 to 100

8. COLOUR = white , yellow , cream coloured , smooth or beaded
structure
ABSENCE = they are absent in collembola and the family of
aphididae of the order HOMOPTERA

9. Histology of Malpighian Tube
The malpighian tubules are composed of two or eight cells
and are of various shapes and sizes . They are either
produced with distinct cell boundaries or are syncitial the
cells are either smooth or have a brush or honey comb
border towards the lumen the cells rest on a thin basement
membrane covered by a peritonial membrane occasionally
containing five muscle fibers which bring about the
peristaltic movement of the tubules the movement caused
by the muscles of the tubules assures the mixing of the
contents .the tubules carries the contents towards the hind
gut for find disposal

11. Function of Malpighian Tube
1. This is chiefly excrete uric acid which is usually accompanied by
water . The process of excretion takes place as follows
The uric acid collected in the body cells diffuse into the blood
which finally circulates round the malpighian tubules in the blood uric
acid combines with sodium and potassium carbonates to form
sodium and potassium urates .
 These two salts are soluble in water and are easily absorbed by
the distal part of malpighian tubules in this way the urate salts are
secreted into the lower of the malpighian tubules within the proximal
part of tubule in alkaline pH by the action of carbonic anhydrates .
 The urate salts are broken down to regenerate water bicarbonates
and uric acid the water and bicarbonates are reabsorbed and free
uric acid is precipitated from here the uric acid solution loosely
termed as ‘urine ‘ is passed into the proctodaeum and is finally
excreted through the anus

12. It may be mentioned that this method of excretion involves a constant
supply of water and in the majority of the insects .water is a very
impotent constituent and can not be lost so easily
In aquatic insects which are not compelled to conserve water excretion
of uric acid accompanies a good deal of water . However in these to
deprive the insects of essential ions such as chlorides sodium
potassium . in order to eliminate this deficiency some aquatic larvae
have a body covering which is highly impermeable to salts . The anal
papillae can absorb the substances present in the fresh water
OTHER ASCCESSORY FUNCTION
1. Spittle secretion in spittle bug
2. Light production in Bolitophila
3. Silk production in larval neuroptera

13. LABIAL GLANDS
In collembola and thysnaura where the malpighian tubules are
absent. The labial glands are excretory in function , they have an
upper sac like part a coiled labyrinth with a gland and excretory
duct which opens at the base of labium
The labial glands take up dyes from the blood and eliminate
outside

14. NEPHROCYTES
In some insects special cells . The nephrocytes perform the function of
excretion . These cells are either pericardial cells distributed along the
dorsal heart or garland like string of cells
They also known by pericardial cells they are large and are often
binucleate they are always found to have an acid reaction mesodermal in
origin
HOLLANDE (1922) give description about the pericardial cells.
They are agents for breaking down complex colloids which are
transformed by ferments produced in the cells into crystalloids

15. Urate cells
Certain insects are provided with special cells in the body which become
loader with crystalline spheres of uric acid .these cells are termed as urate
cells
They serve the function of excretion of uric acid and often of pigments also
these urate cells are regarded as “storage” kidneys and are scattered
throughout the insect body . These cells collect the uric acid in solid form
through out the larval life and the excretory products are finally transferred to
the malpighian tubules in the pupal stage for elimination e. g social
hymenoptera

16. Oneocytes
The cells of haemocoel epidermis or fat body with many functions
Origin- ectodermal
Present usually near the abdominal spiracles and sometimes remain
closely associated with the bases of the epidermal cells
They usually amber colored
The functions of the oenocytes are still problematic they have been
thought to secrete cuticular lipids but their ultra structure resembles
that of vertebral cells concerned with steroid synthesis and it has
even been suggested that they may be the site of ecdysone
production

17. Excretion by Gut and Rectum
According to WATERHOUSE and DAY tn collembola the mid gut
performs the functions of excretion in case of aphids the excretory
materials and the pigments are eliminated by the digestive tract in
Periplaeta the uric acid is present in the form of crystals and not in liquid
form in the wall of hind gut accordingly the hind gut does the functions of
excretion to some extent in this insect some insects excrete ammonia
which appears to pass directly into the digestive tract with out going to
the malpighian tubules e.g. in blourflty larvae the ammonia is produced in
the mid gut and is then reabsorbed and passed via blood to the hind gut.
In aquatic insects the ammonia may be secreted directly into the rectum .

18. NITROGEN EXCRETION
Terrestrial insects excrete waste products as uric acid or certain of
its salts called urates which were water insoluble and requires
less amount of water for waste product removal this type of
excretion is known as “URICOTELISM”
In aquatic insects ammonia is the excretory products which is
poly soluble in water and requires more amount of water for waste
product removal
This type of excretion is known as “AMMONOTELISM”

19. CRYPTONEPHRY
The distal ends of the malpighian tubules are held in contact with the
rectal by the perinehric membrane . Which is concerned either with
efficient dehydration of faeces before their elimination or ionic regulation
example larval symphyta

20. STORAGE EXCRETION
The excretory waste materials are retained with in the body in
different sites
Uric acid is stored as urates in the cells of fat body e.g. –
American cockroach
Uric acid is stored in the body wall giving white color e.g.:-
Red cotton bug
Uric acid is stored in the male accessory glands to produced
the outer coat of spermatophore which is excreted during
copulation
Uric acid is stored in the wing scales giving white color
example butterfly