Insect general morphology head antennae mouthparts

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Insect general morphology head antennae mouthparts Powered By Docstoc
					Prepared by : Reem Alajmi
                       Course contents
•    Insect in relation to other Arthropod (introduction)
•   Insect general morphology
•   Head and its appendages
•   Thorax and its appendages
•   Abdomen and its appendages
•   The structure and function of integument
•   Internal organs:
•      The digestive system
•      The execratory system
•      The circulatory system
•      The nervous system
•      The respiratory system
•      The endocrine system
•   Insect development (Metamorphosis)
•   Insects classifications
            Teaching Philosophy

             Learning        Understanding

New ideas


   Pose           Thinking
     Teaching Philosophy


•   Examination
•   Lab Exam
•   Quizzes
•   Reports
•   Attendance
•   Lab Notebook
•   Insect Collection
            All arthropods possess

• Exoskeleton - a hard protective covering around the
  outside of the body (divided by sutures into plates
  called sclerites)
• Segmented body - that allows movement
• Jointed limbs and jointed mouthparts - that allow
  extensive specialisation
• Bilateral symmetry - whereby a central line can
  divide the body into two identical halves, left and
• Ventral nerve chord - as opposed to a vertebrate
  nerve chord which is dorsal
• Dorsal blood vessel

Other Animals

Other Arthropoda
    Major groups of Arthropods

Class Arachnida (Scorpions & Spiders)
Class Chilopoda (Centipedes)
Class Diplopoda (Millipedes)
Class Crustacea (Shrimps, Crabs, Lobsters)
Class Insecta (Insects)
               All insects possess

•   3 body parts (head, thorax and abdomen)
•   6 legs
•   1 pair antennae
•   Most adults have wings
                  Insect head

• Strongly sclerotized rigid capsule.
• Insect head carrying:
   - mouthparts
   - sense organs (Antennae)
   - compaound eyes and ocelli.
               Rigidity of head

• Head is continously sclerotized capsule with
  no outward appearance of segmentation, but
  it is marked by a number of grooves known as
  sulci (sulcus).
• The sulci are variable in position in different
  species, and some of them may be completely
• Sulcus: impressed line separating sclerites.
• Suture: is the groove marking the boundaries
  between segments.
         Rigidity of head con…
• The need of culci for strengthening the head.
• Examples of sulci:
  - Epistomal (frontoclypeal) sulcus.
  - Subocular sulcus.
  - Circumocular sulcu.
  - Circumantennal sulcu.
• The sulci defined into different areas:
       Rigidity of head Con…
- The Front of the head, the frontoclypeal area
  is divided by the epistomal sulcus (fronto-
  clyeleal sulcus) into the frons above and the
  clypeus below (both attached to variable
  muscles run into the pharynx, labrum,
  hypopharynx and cibarium).
- Dorsally the frons contenious into the vertex
  which separated from the occiput by the
  occipital sulcus.
           Rigidity of head Con…

• The lateral area of the head beneath the eyes
  is called the gena, from which the subgena is
  cut off below by the subgenal sulcus.
• The region of the subgena above the mandible
  is called the pleurostoma and that part behind
  the mandible is the hypostoma.
         Rigidity of head Con…

• In all insects the rigidity of the head is
  increased by four deep cuticular invagination,
  known as apodemes, which usually meet
  internally to form a brace for the head and for
  the attachment of muscle. The structure
  formed by these invagination called tentorium
- internal support for the head capsule

Posterior arms

                                                               Anterior arms

 Dorsal arms

                           Cut away view of the head capsule
                 Head orientation

1- Hypogantous: If the head is oriented so that the
   mouthparts lie ventrally. In this position mouthparts
   directed downward toward the ground
2- Prognathous: If head is directed anteriorly. In some
   insects, especially those that pursue their prey or use
   their mouthparts in burrowing the mouthparts are
   directed anteriorly in front of the insect.
3- Opisthognathos: mouthparts are directed
   posteroventral in position. So mouthparts are
   directed backward below the insect's body
               Insect antennae
• All insects posses a pair of antennae, but they
   maybe greatly reduced, especially in larval
• Antennal structure
 Each antenna consists of :
 1 - Basal scape. It is inserted into a
   membranous region of the head wall and
   pivoted on a single marginal point, the
   antennnifear so it is free to move in all
             Antennal structure

2- Pedicel
3- Flagellum. It is divided into a number of
  similar annuli joined to each other by
  membranes, so the flagellum as a whole is
  flexible. The number of annuli varies
  considerably depending on the species and
Insect antenna
• The antennae are moved by levator and
  depressor muscle inserted into the scape, and
  by flexor and extensor muscles arising in the
  scape and inserted into the pedicel.
• There are no muscle in the flagellum (in the
  anullated type of antennae ex: locust,
• In Collembola and Diptera, there is intrinsic
  musclature in each unit of the flagellum.
               Antennal sensillae
• The antennae are primarily sensory structure and
  they are rich with sensilla in most insects.
• It is characteristics of insects that the pedicel
  contains a chordotonal organ (Johnstons organ),
  which respond to movement of the flagellum with
  respect to the pedicel.
• Both scape and pedicel have hair plates and a group
  of campaniform sensilla that provide information on
  the positions of the basal segment with respect to
  the head and to each other.
        Antennal sensillae Con…
• Scattered mechanoreceptor hairs are also present on
  the segments.
• The principle of sensilla on the flagellum of many
  insect are olfactory, and these have a variety of
  forms. It is common to contact chemoreceptors,
  mechanorecpetor and thermoreceptor.
• Some time the sensilla are concentrated in particular
  region of the flagellum ex: in Lepidotera, most
  sensilla are aggregated in terminal club.
              Function of flagellum

1- It act as sense organ (mainly olfactory), sometime
   tactile function. Johnstons organ is important in
   regulation of air speed in flying insect. Some time in
   female Drosophila and honey bee workers,
   perception of near-field sounds.
2- Formation of air funnel (water beetles)
3- In newly hatched form Hydrophilus, the antenna is
   facilitated with a number of sharp spines on the
   inside of the antenna, assist the mandible in
   masticating the prey.
        Function of flagellum Con….

4- In fleas and Collembola, the antennae are
  used in mating (male used inner surfac bear
  large number of adhesive discs with a gland
  secreting adhesive material)
Aristate antennae      Setaceous
     Shore fly          antennae
                       Damsel fly

Capitate antennae      Lamellate or
 Speckled wood      clubbed antennae

Clavate antennae       Moniliform
 Carrion beetle         antennae

Plumose antennae     Serrate antennae
  Male mosquito        Click beetle

Filiform antennae   Pectinate antennae
 Longhorn beetle          Firefly

• Insect mouthparts presents in two forms:
 - Endognathous (where m.p. lie in cavity of head
   produced by the gena. ex: Collembola, Diplura and
 - Ectognathous: This form of m.p. is related to diet,
   but two basic types can be recognized, one adapting
   for biting and chewing solid food, and the other
   adapted for sucking up fluids.
             Biting mouthparts

This form of m.p. is consists of :
1- Labrum: is a broad lobe suspended from
  clypeus in front of the mouth and forming the
  upper lip. On its inner side it is membranous.
  Different use of muscles can produce a lateral
  rocking movement of the labrum. It contains
  chemosensory sensilla.
2- Mandibles: It is rotated about its articulation
  by anterior and posterior muscles arising from
  the head. It is short, strongly sclerotized, and
  the cuticle of the casps is often hardend by
  the presence of zinc or manganese.
                   Mouthparts Con…
3- Maxillae: Occupy a lateral position, one on each
   side of the head behind the mandibles. The proximal
   part consists of
a- Basal cardo, which has a single articulation with the head.
 b- Flat plat, the stipes, hinged to the cardo, both are capable of
   movement .
• Distally on the stipes are two lobes (one or both maybe
  a- Inner lacinea.
  b- Outer galea.
  c- More laterally on the stipes is a jointed-leg-like palp made
   up of a number of segments (maxillary palp).



            Mouthparts Con…

4- Labium: It is similar in structure to maxillae, but
  with the appendages of the two sides fused in
  the midline so forming a median plate. The basal
  part is called postmentum, then is the
  prementum which close the pre-oral cavity from
  behind. Terminally it bears four lobes, two inner
  glossae and two outer paraglossae. Which are
  collectively known as ligula. A palp arises from
  each side of the prementum, often being three



             can be fused to
                 form a
5- Hypopharynx: is a median lobe immediately
  behind the mouth. The salivary duct usually
  opens behind it, between it and the labium.
  Most of it is membranous, but the dorsal face
  is sclerotized distally.



Carpenter ant         Stag Beetle           Caterpillar

 Cockroach      Damselfly eating mosquito    Termite
            Sensilla on mouthparts

• Most senilla on m.p. contact chemo-receptors, but
  mechanoreceptors are also common and olfactory
  sensilla are often present on the chordotonal organs.
  Probably function as pressure receptors, are present
  at the tips of mandibular cusps and also in the
  lacinea where this is heavily sclerotized.

• The neck is a membranous region which gives
  freedom of movment to the head. It extends
  from the post-occiput at the back of the head
  to the prothorax.
• Latteraly to the neck membrane are the
  cervical sclerites (1-3) where muscles are
  attached to move the head
Any Questions?
Describe the different types of sensilla
that presents on both antenna and

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