prof. dr. badr el-sabah entomology lecture 3

Lecture 3

Phylum Arthropoda Class: Insecta

Prof.Dr. Badr El-Sabah / Lecture3 1

Thoracic Appendages1- Insects Wings

Typically, there are 2 pairs of wings in insects: one pair on the mesothorax and another pair on the metathorax. The wings are outgrowths of the exoskeleton and consist of a double layer of extremely thin cuticle, throughout which are interspersed numerous veins, as can be seen in the lacewing above.

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Wings adaptations and modifications:


Coleoptera

Elytra -- hard, sclerotized front wings that serve as protective covers for membranous hind wings

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Prof.Dr. Badr El-Sabah / Lecture3

Hemielytra -- front wings that are leathery or parchment-like at the base and membranous near the tip

Hemiptera


Orthoptera, Blattodea, and Mantodea

Tegmina -- front wings that are completely leathery or parchment-like in texture


Diptera

Halteres -- small, club-like hind wings that serve as gyroscopic stabilizers during flight

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Thysanoptera

Fringed wings -- slender front and hind wings with long fringes of hair

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Trichoptera

Hairy wings -- front and hind wings clothed with setae


Lepidoptera

Scaly wings -- front and hind wings covered with flattened setae (scales)


Hymenoptera

Hamuli -- tiny hooks on hind wing that hold front and hind wings together


Frenulum -- is a bristle or group of bristles located near the base of the hindwing

of some butterflies and moths. The frenulum hooks onto the retinaculum, located on the forewing, in order to hold the hindwings and forewings together during flight.

Lepidoptera


2- Insect legs Three pairs of jointed legs arevirtually always present in adultinsects and each leg is normallycomprised of five major segments:coxa, trochanter, femur, tibia andtarsus. The tarsus may be furtherdivided into 2-5 smaller segmentscalled tarsomeres, the last ofwhich may bear a pair of claws. Insome insects, pads (pulvilli)located beneath the claws enablethem to have greater purchase onsmooth surfaces. This may beenhanced by densely packed smallhairs on the pulvilli and in somespecies, like the house fly, thesehairs exude a sticky secretion thatpermits them to walk vertically upa smooth surface such as awindow pane and upside down ona ceiling. 13


Legs adaptations and modifications:


Cursorial -- adapted for running

Ground beetles and Cockroaches


Raptorial -- adapted for catching and holding prey

Praying mantis


Natatorial -- adapted for swimming

Diving beetle


Fossorial -- adapted for digging in soil

Mole cricket


Saltatorial -- adapted for jumping

Grasshoppers, crickets, locusts, katydids19Prof.Dr. Badr El-Sabah / Lecture3

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– Found on:

– caterpillars

– sawflies

– Not segmented likethe true legs

– Not found on adult insects

Abdominal Appendages - Prolegs


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• Segmented sensory organs on the end segment of abdomen.

• Most noticeable on

– earwigs

– cockroaches

– crickets

Abdominal Appendages - Cerci



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• Found only on female insects

• Used for laying eggs

Abdominal Appendages - Ovipositor

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• A modified ovipositor

• Found only on females insects

• Used for defense or catching prey

Abdominal Appendages - Stinger



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HONEY BEE STINGER

The INTEGUMENT

( The EXOSKELETON OR CUTICLE )IN INSECTS


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The insect’s exoskeleton is made up of a series of plates

• These plates are connected by joints or sutures that make the skeleton flexible.

sutures plates

These plates make up the insect’s

exoskeleton.



The outer layer of the exoskeleton is called the cuticle.

•The main component of the exoskeleton is chitin.

Cuticle

The cuticle has an outer waxy layer.

Waxy layer

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Purpose of the Exoskeleton

1. Supports the weight of the body.

2. Protects the body from minor injury.

3. Provides internal attachment point for the muscles.

4. Allows some chemicals to pass in or out of the body.

5. The waxy layer prevents desiccation (water loss).


Exoskeleton and MoltingIn order to grow the arthropod must shed its exoskeleton, and secrete a new and larger

one. This kind of a process is called molting or ecdysis

Among the arthropods the epidermis secretes an external skeleton called the exoskeleton

– To provide strong support provides rigid levers that muscles can attach to andpull against

– To offer protection serves as a barrier to prevent internal tissues from dryingout; important because many arthropods live on land serves as a barrier toprevent infection

• The exoskeleton (cuticle) is composed of a complex glycoprotein which consists of:1. the polysaccharide chitin2. protein bound

• The outer surface of the cuticle is called the epicuticle - contains waxes making thecuticle an inpenetrable barrier.

• The thicker portion is called the procuticle - divided into the exocuticle and theendocuticle


Structure of arthropodiun exoskeleton


Molting


multicellular spine

seta (trichoid sensillum)

acanthae microtrichia

Basic types of cuticular extensions (from which sense organs are

derived).


Qualities of chitin:

• Strength (Ability to cross-link)

• Flexibility

• Resiliance

• Light Weight



THANKS

prof. dr. badr el-sabah entomology lecture 3

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