Entomology Basics and Insect Morphology

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Questions and Answers

What percentage of species on Earth are insects?

90%

What is the estimated range of insect species on Earth?

2.5 to 10 million

Which of the following is NOT a reason why insects are so successful on Earth?

  • Long life cycle (correct)
  • Ability to adapt
  • Ability to fly
  • Small size

What is the hard protective covering around the outside of the body of arthropods called?

<p>Exoskeleton</p> Signup and view all the answers

What are the plates that the exoskeleton of arthropods is divided into called?

<p>Sclerites</p> Signup and view all the answers

Which of the following is NOT one of the five important extant classes of Arthropods?

<p>Amphibians (A)</p> Signup and view all the answers

What are the two segments that make up the body of arachnids?

<p>Cephalothorax and Abdomen</p> Signup and view all the answers

What is the common name for chilopods?

<p>Centipedes</p> Signup and view all the answers

What is the structure that houses the brain, mouthparts, and sense organs in insects called?

<p>Head capsule</p> Signup and view all the answers

Which of the following is NOT a sense organ typically found in the head capsule of insects?

<p>Legs (D)</p> Signup and view all the answers

What is the name of the uppermost sclerite on the dorsal surface of the head capsule?

<p>Vertex</p> Signup and view all the answers

What is the name of the suture that runs along the midline of the vertex and splits into two frontal sutures?

<p>Coronal suture</p> Signup and view all the answers

What is the name of the triangular sclerite that lies between the two frontal sutures?

<p>Frons</p> Signup and view all the answers

The epistomal suture separates the base of the frons from the clypeus.

<p>True (A)</p> Signup and view all the answers

Compound eyes are present in all insects.

<p>False (B)</p> Signup and view all the answers

What are the individual units that make up compound eyes called?

<p>Ommatidia</p> Signup and view all the answers

What are the simple eyes that detect low light or small changes in light intensity called?

<p>Ocelli</p> Signup and view all the answers

Which of the following is NOT one of the five main mouthparts of insects?

<p>Antennae (B)</p> Signup and view all the answers

What is the common name for the labrum?

<p>Upper lip</p> Signup and view all the answers

What is the common name for the mandibles?

<p>Jaws</p> Signup and view all the answers

What are the paired structures that can move at right angles to the body and possess segmented palps called?

<p>Maxillae</p> Signup and view all the answers

What is the fused structure that moves longitudinally and possesses a pair of segmented palps called?

<p>Labium</p> Signup and view all the answers

What is the other main mouthpart, besides the five main mouthparts, that functions as a tongue-like structure?

<p>Hypopharynx</p> Signup and view all the answers

What are the two main functional groups of mouthparts based on their feeding style?

<p>Mandibulate and Haustellate</p> Signup and view all the answers

Mandibulate mouthparts are used for grinding and biting solid foods.

<p>True (A)</p> Signup and view all the answers

Haustellate mouthparts are only used for sucking liquids.

<p>False (B)</p> Signup and view all the answers

What are the needle-like projections used to penetrate plant and animal tissue called?

<p>Stylets</p> Signup and view all the answers

Which of the following insect orders does NOT utilize piercing-sucking mouthparts?

<p>Lepidoptera (A)</p> Signup and view all the answers

What are the long siphoning proboscis of butterflies and moths called?

<p>Nonstylate mouthparts</p> Signup and view all the answers

What kind of mouthparts are used to sponge and suck up liquid food?

<p>Sponging mouthparts</p> Signup and view all the answers

The orientation of the mouthparts on the head affects how the insect feeds.

<p>True (A)</p> Signup and view all the answers

What is the name of the basal segment of the antenna?

<p>Scape</p> Signup and view all the answers

What are the individual segments that make up the flagellum called?

<p>Flagellomeres</p> Signup and view all the answers

Aristate antennae are characteristic of house flies and shore flies.

<p>True (A)</p> Signup and view all the answers

Which type of antennae are characteristic of adult carrion beetles?

<p>Capitate (A)</p> Signup and view all the answers

Filiform antennae have a thread-like shape.

<p>True (A)</p> Signup and view all the answers

Geniculate antennae are characteristic of bees and ants.

<p>True (A)</p> Signup and view all the answers

Lamellate antennae end in nested plates.

<p>True (A)</p> Signup and view all the answers

Moniliform antennae are characteristic of termites.

<p>True (A)</p> Signup and view all the answers

Pectinate antennae have a comb-like shape.

<p>True (A)</p> Signup and view all the answers

What are the two margins of bipectinated antennae toothed like?

<p>Comb</p> Signup and view all the answers

Plumose antennae have a feather-like shape.

<p>True (A)</p> Signup and view all the answers

Serrate antennae have a saw-toothed shape.

<p>True (A)</p> Signup and view all the answers

Setaceous antennae have a bristle-like shape.

<p>True (A)</p> Signup and view all the answers

What are the three parts that the insect thorax is divided into?

<p>Prothorax, Mesothorax, Metathorax</p> Signup and view all the answers

What are the hardened plates that make up the insect thorax called?

<p>Sclerites</p> Signup and view all the answers

What are the dorsal sclerites of the thorax called?

<p>Nota</p> Signup and view all the answers

What is the first segment of the prothorax called?

<p>Pronotum</p> Signup and view all the answers

The notum is the dorsal sclerite of each thoracic segment.

<p>True (A)</p> Signup and view all the answers

The sternum is the ventral sclerite of each thoracic segment.

<p>True (A)</p> Signup and view all the answers

The pleuron is the lateral sclerite of each thoracic segment.

<p>True (A)</p> Signup and view all the answers

The pleural suture divides the pleuron into an anterior episternum and a posterior epimeron.

<p>True (A)</p> Signup and view all the answers

Wings are only found on the mesothorax and metathorax.

<p>True (A)</p> Signup and view all the answers

What are the five structural components of an insect leg?

<p>Coxa, Trochanter, Femur, Tibia, Tarsus</p> Signup and view all the answers

What is the terminal segment of the tarsus called?

<p>Pretarsus</p> Signup and view all the answers

Ungues are a pair of claws.

<p>True (A)</p> Signup and view all the answers

Arolium is a lobe or adhesive pad between the claws.

<p>True (A)</p> Signup and view all the answers

Empodium is a large bristle or lobe between the claws.

<p>True (A)</p> Signup and view all the answers

Pulvilli are a pair of adhesive pads.

<p>True (A)</p> Signup and view all the answers

Cursorial legs are modified for running.

<p>True (A)</p> Signup and view all the answers

Saltatorial legs are modified for jumping.

<p>True (A)</p> Signup and view all the answers

Fossorial legs are modified for digging.

<p>True (A)</p> Signup and view all the answers

Natorial legs are modified for swimming.

<p>True (A)</p> Signup and view all the answers

Raptorial legs are modified for grasping.

<p>True (A)</p> Signup and view all the answers

Scansorial legs are modified for climbing.

<p>True (A)</p> Signup and view all the answers

Insects are the only invertebrates that can fly.

<p>True (A)</p> Signup and view all the answers

Most insects have two pairs of wings.

<p>True (A)</p> Signup and view all the answers

Wings develop as evaginations of the exoskeleton.

<p>True (A)</p> Signup and view all the answers

Wings become fully functional during the larval stage of an insect.

<p>False (B)</p> Signup and view all the answers

Wings can be membranous, leathery, heavily sclerotized, fringed with long hairs, or covered with scales.

<p>True (A)</p> Signup and view all the answers

Most insects have two pairs of wings, one pair on the prothorax and one pair on the metathorax.

<p>False (B)</p> Signup and view all the answers

Which of the following is NOT a function of wings in insects?

<p>Reproduction (B)</p> Signup and view all the answers

Membranous wings are characterized by thin, unscleritized membranes between the veins.

<p>True (A)</p> Signup and view all the answers

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

<p>True (A)</p> Signup and view all the answers

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

<p>True (A)</p> Signup and view all the answers

Tegmina are front wings that are completely leathery in texture.

<p>True (A)</p> Signup and view all the answers

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

<p>True (A)</p> Signup and view all the answers

Hairy Wings are slender front and hind wings fringed with long hairs.

<p>True (A)</p> Signup and view all the answers

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

<p>True (A)</p> Signup and view all the answers

Lance wings are characterized by a wide coastal field in their wing venation.

<p>True (A)</p> Signup and view all the answers

Hamuli are tiny hooks on hind wings that hold front and hind wings together.

<p>True (A)</p> Signup and view all the answers

Frenulum is a bristle near the base of the hind wing that holds the front and hind wings together.

<p>True (A)</p> Signup and view all the answers

The archedictyon is the name given to a hypothetical scheme of wing venation.

<p>True (A)</p> Signup and view all the answers

The Comstock-Needham system names the veins and their branches according to their position relative to the longitudinal veins.

<p>True (A)</p> Signup and view all the answers

The insect abdomen is the third functional region of the insect body.

<p>True (A)</p> Signup and view all the answers

The insect abdomen contains 6-10 segments.

<p>True (A)</p> Signup and view all the answers

Various types of appendages arise from the abdomen.

<p>True (A)</p> Signup and view all the answers

Pregenital segments are the first 7 segments in females and the first 8 segments in males.

<p>True (A)</p> Signup and view all the answers

Genital segments are responsible for reproduction.

<p>True (A)</p> Signup and view all the answers

Postgenital segments contain the anal cerci.

<p>True (A)</p> Signup and view all the answers

Cerci are located near the anus.

<p>True (A)</p> Signup and view all the answers

Dermaptera have forceps-like cerci.

<p>True (A)</p> Signup and view all the answers

Styles are vestiges of the walking limb.

<p>True (A)</p> Signup and view all the answers

The median caudal filament is a thread-like projection arising from the center of the last abdominal segment.

<p>True (A)</p> Signup and view all the answers

Abdominal prolegs are found in Lepidoptera insects, such as butterflies and moths.

<p>True (A)</p> Signup and view all the answers

Abdominal gills are respiratory organs found in some aquatic insects.

<p>True (A)</p> Signup and view all the answers

Cornicles are paired secretory structures located dorsally on the abdomen.

<p>True (A)</p> Signup and view all the answers

Ovipositors are used for oviposition.

<p>True (A)</p> Signup and view all the answers

Ovipositors are formed by the modification of 8-9 abdominal segments.

<p>True (A)</p> Signup and view all the answers

Some Hymenoptera insects, like wasps and bees, have modified ovipositors that function as poison-injecting stings.

<p>True (A)</p> Signup and view all the answers

The male external genitalia is responsible for copulation.

<p>True (A)</p> Signup and view all the answers

The male external genitalia is formed by the modification of the 9th abdominal segment.

<p>True (A)</p> Signup and view all the answers

Flashcards

What is Entomology?

The scientific study of insects.

Why are insects so successful?

They represent about 90% of all known species.

What is a key factor contributing to insect diversity?

Insects are very diverse in their feeding habits.

What is an exoskeleton?

A hard protective covering around the outside of the body.

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How are arthropods structured?

Their bodies are composed of repeating sections.

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How are arthropod appendages designed?

They have jointed limbs and mouthparts that allow for specialization.

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What is bilateral symmetry?

A line can divide the body into identical left and right halves.

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Where is the nerve cord located in an insect?

Insects have a central line of nerves along the underside of their body.

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What is the function of the dorsal blood pump?

Arthropods have a simple heart on the dorsal side of their body.

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What are some examples of arachnids?

Spiders, scorpions, ticks and mites.

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What are some of the characteristics of arachnids?

They have two body segments, a cephalothorax and an abdomen.

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What are chelicerae?

They possess a pair of claw-like appendages called chelicerae.

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What is a chilopod?

Centipedes are a type of chilopod.

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What is a characteristic of chilopods?

They have a pair of antennae.

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What are centipedes' first legs modified for?

The first pair of legs in chilopods are venomous.

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What is a diplopod?

Millipedes are a type of diplopod.

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What are some characteristics of diplopods?

They have a pair of antennae.

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What are some examples of crustaceans?

Crabs, shrimp, lobsters and barnacles are examples.

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What is the body structure of crustaceans?

They have a head, thorax and abdomen, or a cephalothorax and abdomen.

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How can crustaceans be distinguished?

Their body segments can be fused.

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What are some examples of insects?

Beetles, bugs, wasps, moths, flies are a few.

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What is the body structure of insects?

They have three body segments: head, thorax and abdomen.

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What are sensory organs insects have?

They have a pair of antennae.

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What is a characteristic of insect appendages?

They have a variety of appendages with different functions.

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What are some benefits of insects?

Insects contribute to plant pollination, decomposition of organic materials and recycling of nutrients.

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What are some drawbacks of insects?

Insects can damage crops, spread disease and be household pests.

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What are sclerites?

The hard plates that make up an insect's outer skeleton.

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What is the epicuticle?

A thin, waxy layer that repels water.

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What is the procuticle?

A thicker layer under the epicuticle that contains chitin.

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What does the insect head capsule contain?

The head capsule is a compartment that houses the brain, mouthparts and major sense organs.

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What is the vertex?

The upper sclerite of the head capsule.

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What is the epistomal suture?

A deep groove separating the frons from the clypeus.

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How are insect compound eyes structured?

Compound eyes are made up of many units called ommatidia.

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What is the function of ocelli?

Ocelli detect changes in light intensity.

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What is the labrum?

The labrum is often called the upper lip.

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What are mandibles?

Mandibles are highly sclerotized paired structures that move at right angles to the body.

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What are maxillae?

Maxillae are paired structures that possess segmented palps.

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What is the labium?

The labium is often called the lower lip.

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Study Notes

Entomology

  • Insects are a highly successful group, comprising approximately 90% of all species.
  • An estimated 2.5 to 10 million insect species exist, though only around 1 million are described.
  • Insects' success is attributed to factors like small size, adaptability, reproductive ability, diverse feeding habits, short life cycles, exoskeletons, and flight capabilities.

Insect Morphology

  • Arthropods (including insects) are characterized by an exoskeleton, a hard protective covering around the body, divided into plates called sclerites.
  • Their bodies are segmented, with jointed limbs and mouthparts enabling diverse specialization.
  • They exhibit bilateral symmetry, meaning a central line divides the body into mirror-image halves.
  • The insect body plan includes a head, thorax, and abdomen, each possessing characteristic features.
  • Five extant classes of arthropods include arachnids, chilopods, diplopods, crustaceans, and hexapods.

The Importance of Insects to Humans, Environment, and Agriculture

  • Beneficial insects play crucial roles like pollination, decomposition of organic matter, recycling of essential nutrients, and controlling harmful invertebrates.
  • Insects can also be pests, damaging crops, acting as household pests, causing parasites, biting, and stinging problems, or posing threats to livestock and human possessions.

Basic Insect Morphology

  • The exoskeleton is composed of sclerites (hardened plates).
  • The insect cuticle comprises two layers: the epicuticle (a thin, waxy, water-resistant outer layer) and the procuticle, which is further subdivided into exocuticle and endocuticle.

The Head

  • The insect head capsule encloses the brain, mouth opening, mouthparts, and major sense organs (antennae, compound eyes, ocelli).
  • The head's surface is divided into regions (sclerites) by sutures (grooves).
  • Key sclerites include the vertex, frons, and clypeus.

Compound Eyes and Ocelli

  • Compound eyes are composed of numerous ommatidia, enabling acute movement detection.
  • Ocelli are simple eyes that detect changes in light intensity.

Mouthparts

  • Mouthparts vary greatly among insects, falling into two main functional groups: mandibulate (biting/chewing) and haustellate (sucking).

Mandibulate Mouthparts (Chewing)

  • Examples include the mandibles, maxilla pair, and labrum.
  • Used for chewing and biting solid food.

Haustellate Mouthparts (Sucking)

  • Subdivided into types with and without stylets.
  • Stylet-equipped mouthparts penetrate tissues, and those without stylets extract fluids from surfaces like flower nectar.
  • Examples include butterflies and moths with their siphoning proboscis.
  • Also includes piercing-sucking type mouthparts.

Antennae

  • Antennae are sensory appendages on the head, used for olfaction, humidity detection, and changes in the concentration of water vapor.
  • Their structure varies widely among insect orders (filiform, geniculate, lamellate, etc).

Thorax

  • The thorax is divided into three segments (prothorax, mesothorax, and metathorax).
  • Each segment includes hardened plates (sclerites): notum (dorsal), pleuron (lateral), and sternum (ventral).
  • Each segment typically bears a pair of legs; meso- and metathorax may also bear wings.

Legs

  • Legs are typically composed of five segments: coxa, trochanter, femur, tibia, and tarsus.
  • The tarsus often ends with claws, arolium, or pulvilli for attachment.
  • Insect legs are highly specialized for diverse functions (running, jumping, digging, or swimming).

Insect Wings

  • Wings are evaginations of the exoskeleton found on the meso- and metathorax.
  • They vary widely in structure and function (membranous, leathery, scaled), serving crucial roles like flight, protection, and displays

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