Insect Abdomen: Appendages found on the abdomen

Insect abdomen is the third functional region of insect body. It is located behind the thorax and contains 6-10 segments. There are various types of appendages arise from the abdomen.

Cerci

Located close to anus.

-Blattodea: simple and jointed cerci

Via ediacaran.mech.northwestern.edu

-Orthoptera: simple and not jointed cerci

-Dermaptera: Sclerotized, forceps like cerci

Dermaptera forcep like cerci via gallurapestcontrol.com

-Thysanura: Long filamentous cerci

Long filamentous cerci of Thysanura

-Ephemeroptera larvae: Wing like cerci that helps to move forward in water.

Wing like cerci -Ephemeroptera larva

Styles

Can be seen in Cockroach and Lepisma. It is regarded as the vestige of the walking limb.

via microscopy-uk.org.uk

Median caudal filament

This is a thread like projection arising from he center of the last abdominal segment between the cerci.

Abdominal Prolegs

Can be seen in Lepidopera.

via entomology.umn.edu

Abdominal Gills

These are respiratory organs and found in nymphs of some aquatic insects.

Cornicles

These are located dorsally on the abdomen as paired secretory structures.

      

Female External Genitalia

Ovipositors are used for oviposition and it is formed by the modification of 8-9 abdominal segments. Thysanura, Orthoptera, Thysanoptera and some Hymenoptera insects contain true ovipositors.

Ovipositor places egg inside caterpillar 

Egg is released (naturecloseups.com)

-The ovipositor is modified as a poison injecting sting ( Wasps, bees..etc)

via amazingnature.us

-Hind end of the abdomen is extended to work as an ovipositor

Male genitalia

Modification of 9^th abdominal segment makes the copulatory organ of males which is consist of aedeagus and pair of lateral claspers to grasp and hold the abdomen of the female during mating. 

Moulting and cuticle formation of insects

Hormones such as Ecdysone and bursicon play an important role during the events in moulting.

Apolysis

·         Epidermal cells divide and change their shape.

·         These cells separate from the inner surface of the old endocuticle and leave out the sub-cuticular space.

·         This space is consisting of moulting fluid, proteinase and chitinase.

·         These enzymes are inactive in this stage.

Formation of the epicuticle

·         Cuticulin is deposited below the moulting fluid and above the epidermis.

·         This forms the new Cuticulin layer.

·         Inner protein epicuticle is deposited under the Cuticulin layer.

Deposition of new procuticle

·         Deposition of procuticle occurs beneath the Cuticulin layer.

·         After the deposition enzymes in the moulting fluid activate and digest the old endocuticle.

·         Only a thin layer of the old endocuticle is left out.

·         This layer is called as Ecdysial membrane. These lines are located in the median lines of head and thorax.

·         Weak lines appear along this Ecdysial layer.

·         Wax secretion occurs on to the surface of the new cuticle.

Ecdysis

·         Moulting fluid and digested old endocuticle are absorbed.

·         Intake of the air and muscular contractions cause the insect’s body to swell.

·         This leads the old exoskeleton to split open along the weak lines.

·         Insect draws itself out.

·         All parts of the old cuticle are shed.

·         This old cuticle is called as cast skin.

Expansion of the new procuticle

·         New cuticle is soft and pale.

·         At this moment new procuticle expands before it hardens.

Hardening and darkening of cuticle

·         Hardening of the cuticle is known as sclerotization.

·         This forms sclerites which are rigid plates of exoskeleton.

·         It also darkens the cuticle. This is known as tanning.

Deposition of the new endocuticle

·         New endocuticle deposits after the moulting and tanning.

Orientation of insect head: Prognathous, Hypognathous and Opisthognathous

·         Three types of orientation.

                                i.            Prognathous: orientated horizontally. Mouth parts are pointed forward.

                              ii.            Hypognathous: orientated vertically. Mouth parts are pointed down.

                            iii.            Opisthognathous: orientated obliquely. Mouthparts are pointed backward.

Prognathous

·         Mouthparts are pointing forward.

·         Mouthparts are anterior in position.

·         Long axis is horizontal.

·         Mostly carnivore insects have this type of orientation.

·         Ex: Stick insect

Hypognathous

·         Mouthparts are pointing downward.

·         Mouthparts are ventral.

·         Long axis is vertical.

·         Mostly herbivore insects contain this type.

·         Ex: Grasshopper.

Opisthognathous

·         Mouthparts are pointing backward.

·         Mouthparts are directed down between coxae of legs.

·         This is known as proboscis.

·         Long axis is horizontal.

·         Ex: Plant sucking bugs.

Insect Orders

Order Orthoptera

Cricket

Grasshopper

 Order Isoptera

 Odontotermes sp.(Termites)

Order Dermaptera

 Forficula sp.(Ear wig)

 Order Hemiptera

Sub order Heteroptera

 Nezara sp.

Sub order Homoptera

Aphis sp.

Order Hymenoptera

Vespa sp.(Wasp)

Ants

Order Lepidoptera

Moth

Butterfly

 Order Coleoptera

Oryctus rhinoceros (Coconut Black Beetle)

Rhuncophorus sp.(Red Palm Weevil)

 Order Phasmatoidea

Carausius sp.(Stick insect)

Phyllium sp.(Leaf insect)

 Order Mantodea

Hierodula sp.(Mantis)

Order Odonata

Libellago sp.(Damselfly)

Macrogomphus sp.(Dragonfly)

Order Thysanoptera

Thrips sp.

Order Phthiraptera

Pediculus humanus(head louse)

 Order Siphonaptera

Ctenocephalides sp.(Flea)

Order Diptera

Musca domestica

Order Blattodea

Periplaneta americana(Cockroach)

Order Thysanura

Lepisma Sp.(Silver fish)

Insects - External morphology

Basic external features of an insect

The body of an insect is mainly divided into three parts

• Head
• Thorax
• Abdomen

Head contains Antennae, Compound eyes and the mouth parts. Thorax comprises three segments. Usually the thorax bears the legs and the wings.  

Abdomen is consist of 7-11 segments with appendages.

Parts of a leg

Mouthparts

Mouthparts are adapted for feeding. Mainly there are two types.

• Chewing and biting mouthparts
• Sucking mouthparts

Chewing and biting mouthparts of cockroach

Siphoning mouthparts of butterfly

piercing and sucking mouthparts of mosquito

Sponging mouthparts of Housefly

Lapping mouthparts of honeybee

                   

Antennae

Different kind of insects

Silverfish

Head louse

Thrips

Flea

Damselfly

Dragonfly

To know about how to make a bug collection visit http://www.cnr.berkeley.edu/citybugs/studentcorner/MakeABugCollection/MakeABugCollection.htm