Sense organs and nutritive requirements of Insects. Comprehensive ppt

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INTRODUCTION
The sensory organs are primarily responsible for the reception of stimuli and pass them on to the
neuro-muscular system, resulting in the varied behavior patterns of insects. Insects can perceive
sound, light, scent, gravity and temperature in minute quantities often far beyond what can be
detected by other animals.According to the various stimuli perceived, they are classified into the
following:
LITERATURE REVIEW:
The number and variety of insects which produce sounds with specialized apparatus undoubtedly
exceed those of all other living organisms combined, but only a few of these, the crickets,
katydids, grasshoppers, and cicadas, make noises loud enough to be noticeable to man. These are
the so-called singing insects, and their ancestors may well have been the first organisms on earth
to communicate through sound waves transmitted in air. Scientific interest in insect sounds dates
at least to Aristotle, who over two thousand years ago separated two groups of Homoptera on the
basis of whether or not they could produce sounds (Myers, 1929, p. 81). Today a complete
bibliography on sound production and perception in insects would contain several thousand
references.Sound production and perception have arisen in the insects a large number of times,
and consequently a wide variety of structures is involved (Kevan, 1954). Sounds are produced by
insects in five different ways:
(1) By rubbing one body part against another, i.e., stridulation (crickets, katydids, grasshoppers,
bugs, beetles, moths, butterflies, ants, caterpillars, beetle larvae, others)
(2) By striking some body part, such as the feet (band-winged grasshoppers), the tip of the
abdomen (cockroaches), or the head (death-watch beetle) against the substrate
(3) By vibrating some body part, such as the wings, in air (mosquitoes, flies, wasps, bees, others)
(4) By vibrating drum-like membranes called tymbals (cicadas)leafhoppers, treehoppers,
spittlebugs); and
sense organs
chemoreceptors
temperature
receptors
photoreceptors mechanoreceptors

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(5) By forcibly ejecting air or fluid (short-horned grasshoppers). (The Ohio Journal Of Science,
1957)
LITERATURE VIEW (COMPARATIVE STUDY)
Sound-producing and auditory structures may involve almost any part of the insect's exoskeleton.
In different groups, such organs have been found on the mandibles (Acrididae), palpi
(Tridactyloidea), antennae (Phasmidae), head capsule (Anobiidae), pronotum (Cerambycidae),
mesonotum (Elateridae), metanotum (Prophalangopsidae), forelegs (Tettigonioidea), middle legs
(Lucanidae), hind legs (Passalidae), forewings (Tettigonioidea, Acridioidea), hind wings
(Acridioidea), several of the abdominal segments (Coleoptera, Orthoptera, Homoptera), and the
cerci (Blattidae). Many species possess two sets of sound-producing organs (Corixidae) or
auditory organs (Gryllidae).
1. Mountain Cricket :
The sounds of field crickets are produced by vibration of the tegmina, or forewings. As the
tegmina are closed, a transverse row of minute teeth (file) on the lower side of the upper

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tegmennear its base is scraped by a dorsally-projecting sharp-edged structure (scraper) on the
median edge of the lower tegmen. In the calling song the tegmina are held at a 45° angle with the
body; in courtship they are lowered and tilted roof-like over the abdomen.
2. Cicadas:
The chief mechanism of sound production in cicadas is well-described by Pringle (1954). Two
stiff, convex membranes (tymbals) at the base of the abdomen are alternately buckled inward by
the contraction of a pair of large muscles attached to their inner edges, and popped back outward
through their own resilience. This action may be compared to dimpling a plastic table tennis ball
by pressing it with the thumb and then removing the thumb, thereby allowing the dimpled area to
pop back to its normal shape. The drop in pitch near the end of the "Pharoah call"
(congregational song, fig. 9) of the seventeen-year cicada corresponds to a lowering of the
abdomen, which is slightly elevated during the rest of the call. In many cicadas rapid up-and-
down motion of the abdomen provides a secondary pulsation which is superimposed on the more
rapid rhythm due to the in-and-out popping of the tymbals.
3. Red Milkweed Beetle:
The noise made in this situation is a rather noticeable, shrill squeaking (fig. 12), produced by
rubbing together stridulatory structures on the back of the pronotum and the front of the
mesonotum. Several individualswere taken into the laboratory and placed on the leaves and
blossoms of milkweed (Asclepias sp.) in a quart jar.
SENSE ORGANS
MECHANORECEPTOR
Mechanoreceptors are the sense organs of insect, which respond to the sense of touch due to
contact with external solid objects, current of air and water or even because of internal body
pressure.The principal mechanoreceptors are:
The Trichoid Sensilla
The Companiform Sensilla
The Chordotonal Organ

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.
A. B.
Fig. 1. (A) Trichoidsensillum , (B) Campaniform organ , (C) Chordotonal organ
The tactile organs or trichoidsensilla
THE TRICHOID SENSILLA:
They are the simple articulated sensory hairs and distributed on the entire body surface and
commonly called as the sensilla.
Location of tactile organs:
Trichoidsensilla present on the antennae, tarsi, tibia and cerci. These organs of the insects
sub-serving the sense of touch.
Functions of tactile organs
a. There are some trichoid hair plates at the joints of various appendages and function as
proprioceptors during sliding of the segments over each other.
b. There are tactile hair- beds on the facial region of the head of locusts and Lepidoptera, on
the neck of dragonflies, on the wing margins of Lepidoptera which are responding to the air
movements during flight.
c. The tactile hairs of the antennae and lower segments of legs perceive earth-bornvibrations
in terrestrial insects and water surface vibrations in aquatic insects.

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THE CAMPANIFORM SENSILLA:
The campaniformsensilla cannot be seen externally but recognized from the dome-shaped
cuticular areas. They elevated above or depressed below the general body surface. Cell
structure and arrangement is similar to that of trichoidsensilla.
Location:
They occur in various parts of the body, wing-base, halteres, cerci, palps and on the base of
trochanter, femora, tibia and tarsal segments.
Functions
a. The campaniformsensilla function as the proprioceptors.
b. They respond to the mechanical stimuli, in terrestrial insects, water pressure in aquatic
insects and air pressure in flying insects.
CHORDOTONAL ORGAN
Chordotonal organ consists of single unit or group of similar unit is called scolopidia. They
are sub-cuticular and are attached to the cuticle at one or both end often no sign of their
presence. Each scolopidia consists of three cells:
a. Neuron
b. Scolopale cell or enveloping cell
c. Cap cell
Location:
The chordotonal organs occur in legs at femoral, distal tibial and tibio-tarsal regions, in
abdomen and wing base.
Specialized chordotonal organ
a. Johnstons organ
b. Auditory or tympanal organ
Johnstons organ
Jonstons organ is a specialized chordotonal organ in the 2nd antennal segment, occurs in all
adult insect except Collembola and Diplura. It consists of single mass or several groups of
scolopidia and is highly developed in Culicidae, where the pedicel is enlarged. Axon of sense

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cells run back and enter the antennal nerve. It perceives movement of antennal flagellum and
flight speed indicator.
Fig. 2. Jhonstons organ
Auditory or tympanal organ:
Tympanal organs are present in the adult of many insect species. Tympanal organ consists of
a thin layer of cuticular structure, called tympanic membrane, air sac and a group of
chordotonal organ. Tympanic membrane and air sac form drum, sound waves that strike the
drum cause it to vibrate and therefore the sensilla to be stimulated(Robert D, 1996).They are
located
 Between metathoracic legs of mantids.
 Metathorax of many nectuid moths.
 Prothoracic legs of many orthopterans.
 Abdomen of short horned grasshopper and cicada.
 Wings of certain moths and lacewings.
Fig. 3. Tympanal organs in different insects

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CHEMORECEPTOR
Chemoreceptor is sensitive to chemicals, stimulation by chemicals can occur in the following
different ways:
1. Olfactory or smell chemoreceptor:
They provide sense of smell. Mechanism of perception of chemicals in gaseous state at high
concentration is known as olfaction.
2. Gustatory or contact chemoreceptor:
They provide sense of taste. Mechanism of perception of chemicals in liquid state at high
concentration as known as contact chemoreceptor.
Fig.4. Insects Chemoreceptors
Functions of chemoreceptor
Chemoreception, essentially taste (gustation) and smell (olfaction), is an extremely significant
process in the Insecta, as it initiates some of their most important behavior patterns that is section
of food, oviposition site, location of host or mate, and responses to commercial attractants and
repellents.
Location of chemoreceptor
Organs of taste are common on :
i. The mouthparts, especially the palps,
ii. The antennae (Hymenoptera),

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iii. Tarsi (many Lepidoptera, Diptera, and the honeybee),
iv. Ovipositor (parasitic Hymenoptera and some Diptera) and
v. General body surface.
Organs of smell are located on the following sites:
i. The antennae are the primary site of olfactory organs and often bear many thousands
of these structures.
ii. The mouthparts also carry olfactory structures in many species.
PHOTORECEPTORS
Photoreceptors may be defined as the ability to perceive light in visible or near visible range of
the electromagnetic spectrum. Organism have to be a pigment capable of absorbing light of a
given wave length and a means of producing a nervous impulse as a result of this
absorption.Three types of photoreceptive structures found in insects:
1. Compound eyes
2. Dorsal ocelli
3. Lateral ocelli (stemmata)
Compound eyes
Most adult insects have a pair of compound eyes. The compound eyes are composed of a large
number of alike structural units called ommatidium. The number of ommatidium varies from
insect to insects.
Fig. 4. Compound eye(ommatidium)

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The structural parts of an Ommatidium
The ommatidium consists of the followings structural parts:
i.The cornea:
It is outmost part of the ommatidium. It is transparent, colorless and biconvex modified cuticular
area often termed as a facet or lens.
ii. The corneagen cells:
They are the epidermal or hypodermal cells lying behind the cornea. A group of two corneagen
cells secretes a single lens.
iii.The cone or semper cells:
Beneath the cornea, there are four distinct cells. Generally they secrete the crystalline and form a
cone. In most cases, these cells are represented by the nuclei only, called the semper cells.
iv.Theretinula cells:
The crystalline cone is followed by a long retina forming a basal part of an ommatidium. It is
firmed from a group of alike seven retinula cells as pigmented visual cells. Each retinula cell
posteriorly terminates above the basement membrane and gives out a post retinal axonal fibre
running towards the optical lobe. The inner margin of the retinula cell lying around the
ommatidial axis is highly differentiated from rest of the cell body, and it is called the
rhabdomere. These rhabdomere of all 7 retinula cells extend the whole length of the retina and
form a rhabdom. The rhabdom is nothing but an internal optic rod having a fibrillar structures,
and it becomes a central axis of retina.
v.The pigment or iris cells:
There are two groups of iris cells, one around the crystalline cone cells and the other around the
retinula, called the primary and secondary iris cells, respectively. Each group of iris cells is

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composed of six cells arrange in a short of circlet. The secondary iris cells separate one
ommatidium from the neighbour one.
Fig. 5. Occeli
The mechanism of image formation:
i.The apposition mechanism:
It is a mechanism of image formation in the bright day light by most of the diurnal insects. The
pigment cells envelop the ommatidia completely and thus the rays of light can enter from the
central point of the dioptric apparatus. Different ommatidia finally produced a single complete,
erect image of an object.
ii.The super position mechanism:
It is a mechanism of image formation in poor light generally during night, mostly the nocturnal
insects. At night time the pigment cells become contracts so that the light from the wide visual
field can enter to the rhabdom of retinula cells obliquely. So light can enter centrally and
obliquely. Each rhabdom therefore receives the light from several cones of neighboring
ommatidia. Hence there is an overlapping of points of light. The image thus formed from a group
of rays refracted by neighboring cones, called the superposition image. It is erect in position and
represents merely a part of an image. The compound image is formed after an amalgamation of
all such images and it is the final form of a complete superposition image.
NUTRITIVE REQUIREMENTS
The main reason any animal eats is to acquire the nutrients (including water) that are essential
for meeting energetic needs associated with general maintenance and fueling growth and

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reproduction. In this regard, insects do not differ from other animals. What sets insects apart,
however, is that they are able to get their nutrients from a wide range of different food sources
that, for various reasons, are unavailable to most other animals. For example, termites and many
beetles feed on wood, while cockroaches and crickets feed on dead plant material (detritus). A
large number of insects have sucking mouthparts that allow them to feed on plant phloem (e.g.,
aphids) and plant xylem (e.g., spittlebugs and cicadas), or in the case of the sucking lice and
some flies (e.g., mosquitoes) vertebrate blood. Some ants and beetles even get their nutrients
from fungus gardens that they themselves actively maintain. (Chapman,1998).The nutritional
needs of an insect are not constant, but vary with the requirements of growth and development,
reproduction, and so on. (Simpson,1990).
The food ingested and digested by the insect must fulfil its nutritional requirements for normal
growth and development to occur. These requirements are complex and although most nutrients
must be present in the diet, some may be obtained from other sources. Some nutrients may be
accumulated and carried over from earlier stages of development, others may be synthesized by
the insect from different dietary constituents, while others may be supplied by micro-organisms.
A number of substances, particularly amino acids and vitamins, are essential for any
development to occur, others while not essential, are necessary for optimal development. The
balance between different constituents is also important. In the absence or imbalance of certain
requirements growth may not occur, or may be impaired, or moulting may not occur.
(Raubenheimer,2000).
LITERATURE REVIEW
In general, polyunsaturated fatty acids such as linoleic and linolenic acids are essential in insect
nutrition. Insects are either unable to synthesize them altogether or incapable of synthesizing
them in sufficient quantities. The inability of insects to synthesize polyunsaturated fatty acids
has been confirmed in some species, and limited capacity has been observed in other species
such as mosquitoes, aphids, and cockroaches (Downer, 1978; Chapman, 1998). Derivatives of
polyunsaturated fatty acids, known as eicosanoids, stimulate oviposition in crickets and may be
important for reproduction in all insects (Chapman, 1998).
The nutritional requirements of entomophagous insects are similar, and similar to those of
nonentomophagous species. House (1977) referred to this common feature of insect nutrition as
the “rule of sameness” (House, 1966a, 1974). The rule has been confirmed by studies with
parasitic and predaceous insects. In assessing the essentiality of nutrients, it is important to note
that most studies were conducted by rearing a single generation on a synthetic or semisynthetic
diet (see later subsections on in vitro culture of parasitoids and in vitro culture of predators,
Table 4). Some investigations overlooked the potential contribution of nutrients stored within
the egg. Stored nutrients may support limited development and, in the case of trace nutrients,
supply a sufficient quantity to ensure development of one generation. Studies with the
parasitoids Itoplectisconquisitor (Say) (Yazgan, 1972) and Exeristesroborator (Fabricius)

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(Thompson, 1981a), for example, demonstrated partial larval development on diets lacking
various essential amino acids and B-complex vitamins. Numerous studies have demonstrated
that entomophagous insects have no distinctive or unusual qualitative nutritional requirements
(House, 1977; Thompson, 1981a, 1981b, 1981c, 1981d, 1986a; Grenier et al., 1994; Vinson,
1994)
INSECT FAT BODY: ENERGY, METABOLISM, AND REGULATION
The fat body plays major roles in the life of insects. It is a dynamic tissue involved in multiple
metabolic functions. One of these functions is to store and release energy in response to the
energy demands of the insect. Insects store energy reserves in the form of glycogen and
triglycerides in the adipocytes, the main fat body cell. Insect adipocytes can store a great amount
of lipid reserves as cytoplasmic lipid droplets. Lipid metabolism is essential for growth and
reproduction and provides energy needed during extended nonfeeding periods. The insect fat
body plays an essential role in energy storage and utilization. It is the central storage depot for
excess nutrients. In addition, it is an organ of great biosynthetic and metabolic activity. Fat body
cells not only control the synthesis and utilization of energy reserves fat and glycogen but also
synthesize most of the hemolymph proteins and circulating metabolites. Large amounts of
relevant proteins, such as storage proteins used as an amino acid reservoir for morphogenesis,
lipophorins responsible for the lipid transport in circulation, or vitellogenins for egg maturation,
are secreted by the fat body.Most of the insect’s intermediary metabolism takes place in this
organ, including lipid and carbohydrate metabolism, protein synthesis, and amino acid and
nitrogen metabolism. Some metabolic processes are stage specific such as the synthesis and
secretion of storage proteins into the hemolymph that occur in the feeding larva or the synthesis
of vitellogenin in adult insects.
To perform multiple metabolic functions to fulfill the changing physiological needs of the insect
during development, the fat body must be able to integrate signals from other organs. Many of
these functions are hormonally regulated, and thus the fat body is the target organ of several
hormones. At the same time, the fat body responds to the metabolic requirements of the organ

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itself. Therefore, several metabolic processes in the fat body must be tightly coupled to a number
of metabolic pathways.
The fat body coordinates insect growth with metamorphosis or reproduction by storing or
releasing components central to these events. In addition to its role related to storage and
utilization of nutrients, the fat body is an endocrine organ, produces several antimicrobial
peptides, and participates in detoxification of nitrogen metabolism. The storage function of the
fat body is fundamental in the life of holometabolous insects. During the larval feeding stages,
energy reserves are accumulated to be used during metamorphosis as well as to provide reserves
for the new adult. Insects need to accumulate at least a minimal amount of nutrient storage to
survive through metamorphosis.
Fig. 7. Fat body of insects.
EXOCRINE AND ENDOCRINE GLANDS OF INSECTS:
Exocrine glands are glands that produce and secrete substances onto an epithelial surface by way
of a duct while the endocrine system is a system of glands that make hormones.
EXOCRINE GLANDS:
Exocrine glands are organs of cardinal importance in all insects. The more common ones include
mandibular and labial glands of cephalic origin (although the latter are often pushed backwards
into thorax or abdomen), dorso- or ventroabdominal and pygidial glands, and silk glands of
manifold embryogenetic origins(Billen, J.& Wilson, E.O., 2007).
Structural variety of exocrine glands In their pioneer paper of 1974, the French termitologists
Charles Noirot and André Quennedey presented a still actual and generally followed
classification of the exocrine glands based on the cellular organization of their secretory cells.

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Structurally most simple are the class-1 cells, that are epithelial cells directly modified from the
tegumental epidermis. Class-2 cells were described to be located more basally in between the
class-1 cells, without being in contact with the apical cuticle.
ENDOCRINE GLANDS:
This is the system of the glands that make hormones.A hormone is a chemical signal sent from
cells in one part of an organism to cells in another part (or parts) of the same individual. They
are often regarded as chemical messengers. Although typically produced in very small quantities,
hormones may cause profound changes in their target cells. Their effect may be stimulatory or
inhibitory. In some cases, a single hormone may have multiple targets and cause different
effects in each target. There are at least four categories of hormone-producing cells in an
insect’s body:
1. Endocrine glands ; Secretory structures adapted exclusively for producing hormones and
releasing them into the circulatory system.
2. Neurohemalorgans ; Similar to glands, but they store their secretory product in a special
chamber until stimulated to release it by a signal from the nervous system (or another
hormone).

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3. Neurosecretory cells ; Specialized nerve cells (neurons) that respond to stimulation by
producing and secreting specific chemical messengers. Functionally, they serve as a link
between the nervous system and the endocrine system
4. Internal organs ; Hormone-producing cells are associated with numerous organs of the
body, including the ovaries and testes, the fat body, and parts of the digestive system.
Together, these hormone-secreting structures form an endocrine system that helps maintain
homeostasis, coordinate behavior, and regulate growth, development, and other physiological
activities.
PROTHORACIC GLANDS:
In insects, the largest and most obvious endocrine glands are found in the prothorax, just behind
the head. These prothoracic glands manufacture ecdysteroids, a group of closely-related steroid
hormones (including ecdysone) that stimulate synthesis of chitin and protein in epidermal cells
and trigger a cascade of physiological events that culminates in molting. For this reason, the
ecdysteroids are often called “molting hormones”. Once an insect reaches the adult stage, its
prothoracic glands atrophy (wither away) and it will never molt again(Chapman, 2013).
Fig : Prothoracic glands
Prothoracic glands produce and release ecdysteroids only after they have been stimulated by
another chemical messenger, prothoracicotropic hormone (PTTH for short). This compound
is a peptide hormone secreted by the corpora cardiaca, a pair of neurohemal organs located on
the walls of the aorta just behind the brain.

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CORPORA CARDIACA
The corpora cardiaca release their store of PTTH only after they receive a signal from
neurosecretory cells in the brain. In a sense, they act as signal amplifiers sending out a big
pulse of hormone to the body in response to a small message from the brain.
CORPORA ALLATA
The corpora allata, another pair of neurohemal organs, lie just behind the corpora cardiac. They
manufacture juvenile hormone, a compound that inhibits development of adult characteristics
during the immature stages and promotes sexual maturity during the adult
stage.Neurosecretorycellsin the brain regulate activity of the corpora allata, stimulating them to
produce JH during larval instars, inhibiting them during the transition to adulthood, and
reactivating them once the adult is ready for reproduction.
NEUROSECRETORY CELLS:
They are found in clusters, both medially and laterally in the insect’s brain. Axons from these
cells can be traced along tiny nerves that run to corpora cardiaca and corpora allata. The cells
produce and secrete brain hormone, a low molecular weight peptide that appears to be the same
as PTTH. Brain hormone is bound to a larger carrier protein while it is inside the neurosecretory
cell, and some believe that each cluster of cells may produce as many as three different brain
hormones.
Fig. 8 . Insect hormones

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Hormones of other organs:
Many other tissues and organs of the body also produce hormones. Ovaries and testes, for
example, produce gonadal hormones that have been shown to coordinate courtship and mating
behaviors. Ventral ganglia in the nervous system produce one compound (eclosion hormone)
that helps an insect shed its old exoskeleton and another compound (bursicon) that causes
hardening and tanning of the new one. There are still other hormones that control the level of
sugar dissolved in the blood, adjust salt and water balance, and regulate protein metabolism.
Functions of endocrine glands:
.
PHEROMONES OF INSECTS:
Pheromones are chemicals produced as messengers that affect the behavior of other individuals
of insects or other animals. They are usually wind borne but may be placed on soil, vegetation or
various items. Tom Eisner, a foremost authority in the science of chemical use by insects, claims
that each species of insect relies on some one hundred chemicals in its life, to engage in such
routine activities as finding food and mates, aggregating to take advantage of food resources,
protecting sites of oviposition, and escaping predation. It has been found that pheromones may
convey different signals when presented in combinations or concentrations. Pheromones differ
from sight or sound signals in a number of ways. They travel slowly, do not fade quickly, and are
effective over a long range. Sound and sight receptors are not needed for pheromone detection,
and pheromone direction is not limited to straight lines(Happ, G. M. 1969).
COMPARATIVE STUDY
Examples of pheromone use by insects and spiders:
Pheromones have long been known to be important to the lives of insects in mating, as
witnessed, for example, in some of the larger silkworm family moths, where males are noted to
Regulationof
molting.
Determination
of form at
metamorphosis.
Polymorphism.
Regulationof
diapause.
Involvein
reproduction.
Regulationof
behavior

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travel nearly 30 miles to a female, following a pheromone trail in the air. Male Cecropia moths
are estimated to detect and respond to a few hundred molecules of pheromone in a cubic
centimeter of air.
In Honeybee colonies, the queens secrete a glandular substance (a pheromone) that is passed
among worker castes, and this secretion coordinates nearly all activities of the workers. One
control is the non-development of the ovaries of the workers. The normal effect of a sex
pheromone is to attract male mealworm beetles to the female, but it has been found that the first
male to mate with the female then covers her with another pheromone, an anti-aphrodisiac,
which dissuades other males from mating with her(Thornhill, R. 1983).
This strategy may conserve the energy of the female or have other benefits. Some tiny parasitic
wasps are known to have evolved to recognize and follow the sex-attractant pheromones of the
hosts that they parasitize or of the prey that they eat. These wasps come from afar, attracted by
the pheromones of scale insects, and lay their eggs in the bodies of the scale insects. There, the
wasp larvae feed and grow as parasites. Some male cockroaches and crickets produce a
pheromone called seducin from their bodies, on which the females nibble during copulation. This
pheromone is an aphrodisiac.
In 1987, Mark K. Stowe of Harvard University and his colleagues reported that bolas spiders
manufacture and release pheromones that are identical to the sex attractant pheromones of
females of certain night-flying moths. Thus, male moths following the pheromone in the air for
some distance find a spider waiting for them instead of a female moth.
Fig. 9. Functions of pheromones in insects

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Pheromone use for insect control:
The use of pheromones to control phases of the lives of pest species is one method of pest
management. Beet army-worms are a serious pest in cotton-producing areas of the United States,
causing multi-million dollar losses in 1995 in Texas alone. In 1997, researchers reported success
in disrupting mating procedures between male and female Beet army-worms by flooding 35-acre
cotton field plots with sex attractant pheromones. With such a pervasion of female scent, the
males could not find females for more than 100 days. Certain pheromone traps have been
developed and are in common usage by homeowners. Indian Meal Moths (Pantry Moths) are
attracted to a pheromone in a small box lined with a sticky substance and are thus captured for
disposal.
CONCLUSION:
Insects have sense organs and so are responsive to many stimuli in their surroundings, such as
light, heat, touch, chemicals and vibrations. These sense organs allow them to see, smell, taste,
hear and touch their environment. They have variety of receptors which when stimulated, pass
information in the form of nervous signals to the CNS of the insect. The number of signal depend
on how strongly the receptor is stimulated and for how long, and the actions of the insect will
vary accordingly and in case of A thorough knowledge of insect nutrition is essential for
understanding the biology of insects. The study of insect nutrition has recently undergone insect
nutrition a metamorphosis, in that information gleaned from earlier investigations that focused
principally on basic nutritional requirements and rearing technology is now being applied for
understanding the feeding strategies, nutritional ecology, and evolution of insects.
Nutritional physiology and biochemistry are also advancing, with the molecular arsenal available
for Drosophila offering many new opportunities. The neurological bases for food selection and
the role of biogenic amines in regulating food choice are beginning to be understood. The
chemical composition of the hemolymph is now recognized as a dynamic indicator of nutritional
status, affecting food selection and nutrient intake. The metabolic responses of insects to altered
nutritional status and the effects of fat body metabolism on hemolymph composition are also
being investigated. Future studies employing multidisciplinary approaches will continue to
unravel the mysteries of insect nutrition and its consequences and significance to insect biology.

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