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Digestive System of Grasshopper:

Alimentary Canal of Grasshopper :

The alimentary canal of grasshopper consists of three principal regions, viz., foregut, midgut and
hindgut.

The foregut or stomodaeum starts at the mouth surrounded by the mouth parts and opening into a
very short muscular pharynx. The pharynx leads into a short, narrow, slender and tubular
oesophagus which enlarges into a dilated conical sac-like and thin-walled structure, the crop
extending up to the posterior end of the thorax.

The crop abruptly dilates to form a thick hard slightly conical structure, called proventriculus or
gizzard. The proventriculus is thick-walled owing to the presence of a large powerful circular muscle
which operates a number of hard chitinous plates bearing teeth. This complicated structure is an
important masticatory apparatus and grinds the solid food.

A large sphincter muscle at the hind end of proventriculus forms the cardiac valve to control the
passage into the midgut. A pair of small branched salivary glands are found attached to the ventral
side of oesophagus and crop. The ducts of salivary glands open into the mouth cavity at the labium.
The foregut is lined internally with the chitinous intima.

The midgut or mesenteron is the ventriculus or stomach. It is a very prominent nearly straight tube
situated within four to five abdominal segments from the cardiac sphincter to the points of origin of
Malpighian tubules. Its transparent membranous walls are not lined with cuticle as in the foregut.

A series of six double finger-shaped hepatic caeca or gastric caeca arise from its anterior end in two
groups; the first group of thick broad pointed tubes is directed forwards, while the second group of
slender ones points posteriorly. These open independently into the anterior end of midgut.

The pyloric sphincter located in the sixth abdominal segment marks the posterior end of
mesenteron. A number of fine thread-like pale yellow Malpighian tubules take their origin from this
area and may be seen floating about in the haemocoelomic cavity independently.
The hindgut or proctodaeum consists of an enlarged anterior portion, the ileum, a narrow middle
portion, the colon and a slightly dilated but very thin-walled prominent rectum opening outside by
an anus. The hindgut is lined internally by the chitinous intima.

Feeding and Digestion of Grasshopper:

The grasshoppers feed on the vegetable food. Food is held by the forelegs, labrum and labium,
lubricated by the salivary secretion (which contains some enzymes) and chewed by the mandibles
and maxillae. Chewed food is stored in the crop. It passes onwards into the gizzard little by little,
where it is further pulverized, strained and passed on into the stomach.

The glands in the walls of stomach and hepatic caeca secrete a few enzymes which bring about
digestion. The slightly alkaline or acidic secretions of midgut contain maltase, lipase, lactase,
protease, trypsin and erepsin. The absorption of food material takes place in the midgut.

By the time the food material reaches the rectum the maximum nutritive material has been availed
and the excess water is absorbed in the rectum. The undigested material or residue is transformed
into slender faecal pellets to be ejected out through the anus.
4. Circulatory System of Grasshopper:

The circulatory system is an open one (lacunar), for there are no capillaries or veins. It is much
reduced compared with many other arthropods. There is a single, slender, tubular and pulsatile
heart lying mid-dorsally in the abdomen. It is suspended in a shallow pericardial cavity formed by a
delicate transverse diaphragm which stretches across the concave inner surface of the tergites.

The heart has a number of side- openings named ostia which are provided with valves to permit the
flow of blood in one direction only. A number of muscular strands, the alary muscles are divergently
spread out fan-wise over the diaphragm to enlarge and reduce the cavity of pericardium by their
contraction and relaxation.

Fibres of one muscle meet those of the corresponding muscle of the other side beneath the heart. In
between the points of attachment of the alary muscles, there are spaces on either sides, through
which the blood from haemocoelomic cavity passes into the pericardial sinus.

A wave of contraction over the diaphragm closes, the interspaces and pushes the valves of ostia to
pump the blood into the heart. On pulsation of this structure the blood flows anteriorly into the
head region through a long dorsal aorta and returns to the haemocoelomic cavity.

Anatomically the heart and aorta can be distinguished by the presence of segmental dilations of the
tube, known as chambers of the heart. There are generally such seven chambers in grasshoppers.
Ostia are, thus, crescentic openings in their lateral walls. Aorta is the thoracic part of the dorsal
vessel and after passing through the thorax, enters the head.
Besides the dorsal diaphragm, there is a ventral diaphragm which forms a continuous sheet from the
pro-thorax to the end of the body and encloses a perineural sinus below. The blood circulates
throughout even into appendages and wing veins, although closed veins or capillaries are wanting.

The blood plasma contains colourless blood cells which act as phagocytes to remove foreign
organisms. The blood serves mainly to transport food and waste material. Fat bodies consist of
loosely aggregated masses of yellow cells completely enveloping the various organs and nerve cord,
more or less acting as a sheath. They store the food for use under adverse conditions.

5. Respiratory System of Grasshopper (Locust):

The respiratory system consists of a network of ectodermal tubes, the tracheae that communicate
with every part of the body. The tracheae consist of a single layer of cells and are lined with cuticle.
The largest tracheal tubes possess spiral threads of chitin, the taenidia which prevent them from
collapsing.

The spiracles on each side of the body lead by branches into a longitudinal trunk. The finest
tracheae, the tracheoles are connected directly to the body tissues to deliver oxygen and carry away
carbon dioxide. The small blind endings of the tracheoles, on the muscles and other organs, are filled
with fluid. During activity of the muscle the concentration of substances in the body fluid around the
tracheoles increases.

This causes diffusion of water from the tracheole into the surrounding area, thus, bringing oxygen
into closer proximity to the site where it is being used as the air moves farther down into the blind
tip of tracheole. After activity stops, the metabolic products that changed the osmotic pressure are
disposed of and the water returns to the tracheole.

There are also several thin-walled air sacs in the abdomen which pump air in and out of the tracheal
system by the alternate contraction and expansion of the abdomen. In the grasshopper the action of
spiracles is so synchronized that the first four pairs of spiracles are open at inspiration and closed at
expiration, while the other six pairs are closed at inspiration and open at expiration.

6. Excretory System of Grasshopper:

The metabolic waste materials from the blood are extracted by the cells of the Malpighian tubules,
passed into the lumen of the tubules and discharged into the intestine for being finally ejected out
through anus. Since the Malpighian tubules lie in the haemocoel, they remove uric acid, urea, urates,
calcium carbonate and oxalate and salts.

9. Reproductive System of Grasshopper:

The sexes are separate and the distinction between male and female grasshopper can be
determined by the posterior ends of abdomen. In the male it is round; in the female it is pointed
because of ovipositor.

Male Reproductive Organs:

The male reproductive organs (Fig. 74.14A) consist of two testes, two vasa deferentia, two seminal
vesicles, single ejaculatory duct, single penis and a pair of accessory glands. Both the testes lie
embedded in a mass of fat bodies above the intestine. Each testis is composed of a series of slender
tubules or follicles in which the spermatozoa develop.

A convoluted tube called the vas deferens leads from each testis. Each vas deferens is dilated
posteriorly into a sac-like structure called seminal vesicle. It narrows down posteriorly and meets a
stout thick-walled prominent accessory gland of its own side.

The size and shape of seminal vesicle and accessory gland differ in different species. The two seminal
vesicles coming from either side meet together forming a common median ejaculatory duct. This
duct opens at the end of a large ventral male copulatory organ, the penis or aedeagus. The accessory
glands apparently secrete a fluid that helps in the transfer of spermatozoa to the female during
mating.
Female Reproductive Organs:

The female reproductive organs (Fig. 74.14 B) comprise a pair of ovaries, oviducts, accessory glands,
a median vagina, and a spermatheca or seminal receptacle. Each ovary is composed of several
ovarioles or ovarian tubules in which a number of ova are produced. Each ovariole is a tapering tube,
the thickness of its walls increases posteriorly.

Since ova are shed into its lumen and descend posteriorly as they grow in size, this tube gives a
beaded appearance owing to varying dimensions of ova in various stages of development. The
terminals of ovarioles are intertwined. Posteriorly the ovarioles meet together to form a common
duct, the oviduct.

Oviducts from either side meet together to form a median short vagina which is slightly thicker and
muscular. It runs posteriorly and opens ventrally between the plates of ovipositor. A pair of
prominent accessory glands meet the vagina independently.

A small sac, the spermatheca or seminal receptacle, joins the vagina by means of a small narrow
duct. During copulation the sperms are received and stored in the seminal receptacle. They fertilise
the eggs as they pass through the vaginal region.

Copulation:

The copulation occurs during late summer. In copulation, the male grasshopper clings to the back of
female and inserts his penis into her vagina and transfers spermatozoa. The spermatozoa are stored
in the seminal receptacle until the eggs are laid. Copulation may take place several times before the
female starts to lay eggs.
Fertilisation:

The mature eggs, 3 to 5 mm long, pass down the oviduct. Each egg is enclosed by a delicate inner
vitelline membrane and a brownish flexible shell or chorion that contains a minute pore or micropyle
through which sperm enters during laying and fertilises the egg. The sperm nucleus unites with the
nucleus of the mature egg and a blastoderm is formed around the periphery of the egg from which
an embryo develops.

Oviposition:

Egg-laying begins a short interval after copulation and continues into the autumn. The female uses
her ovipositor to form a short tunnel or hole in the ground in which eggs are deposited and
surrounded by a sticky secretion that fastens them together as an egg-pod. The eggs are usually laid
in lots of twenty and a single female may lay up to ten lots. The adults die some days after mating
and egg-laying.

Development:

Embryonic development (Fig. 74.16) continues for about three weeks until the embryo is well
formed. The development is then arrested and the embryo enters into a rest period, or dipause, to
tide over the adverse conditions of cold and lack of food in winter. Growth begins again in the spring
when the temperature is warmer.

The young grasshopper that hatches from the egg is called a nymph. It resembles its parent but has a
large head compared with the rest of the body and it lacks wings and reproductive organs. It feeds
upon vegetation and grows rapidly. As the young grasshopper grows and becomes too large for its
inflexible chitinous exoskeleton, which is shed periodically.

The shedding of chitinous exoskeleton is a complex process called moulting. Wings gradually develop
from wing-pads and after five moults the young grasshopper reaches the adult form. This type of
development is called simple or gradual metamorphosis.