Lecture Notes Practice Flashcards: Insect External Morphology and Head/Thorax/Mouthparts

A comprehensive set of practice flashcards covering external morphology, head structure, thorax, wings, abdomen, and mouthparts of insects as described in the lecture notes.

What is a hemimetabolous insect?

An insect whose immature stages (nymphs) resemble the adults and that does not have a pupal stage.

Which two spider groups, along with Araneomorphae, are considered major spider groups in these notes?

Mesothelae and Mygalomorphae.

In external morphology, what does the term 'dorsal' refer to?

The top or back side of the body.

What does 'ventral' refer to in anatomical orientation?

The underside or belly side.

What do the terms 'anterior' and 'posterior' describe?

Anterior = front end; posterior = rear end of the organism.

What does 'proximal' mean in body segment terminology?

Near the point of attachment or origin.

What does 'distal' mean in body segment terminology?

Farther from the point of attachment or origin.

What are the three primary tagmata of insects?

Head, Thorax, and Abdomen.

What are sclerites and sutures in an insect segment?

Sclerites are hardened plates covering each segment; sutures are grooves dividing the sclerites.

Name the seven fused head segments listed in the notes.

Ocular, Antennal, Intercalary, Clypeolabral, Mandibular, Maxillary, Labial.

List key head parts shown (examples include maxillary palp, labial palp, mandible, labrum, maxilla, clypeus, frons, gena, labium).

Maxillary palp, Labial palp, Mandible, Labrum, Maxilla, Clypeus, Frons, Gena, Labium (underneath), Antennae, Ocelli, Eyes.

What are the three light receptor organs on the head?

Eyes (compound eyes), Ocelli, and Stemma (stemmata) on larval stages.

What is a key advantage of compound eyes?

Many ommatidia provide a large field of view and good motion detection; depth perception is relatively challenging.

What are ocelli primarily used for?

Detecting light changes; some can detect polarized light for navigation.

What are stemmata and where are they found?

Visual organs of larval holometabolous insects; generally low resolving power but high light sensitivity.

What are the three main segments of an insect antenna?

Scape, Pedicel, and Flagellum.

What types of sensory cells are common on antennae?

Chemoreceptors, mechanoreceptors, thermoreceptors, and hygroreceptors (via sensilla).

Why are male antennae often more elaborate?

To detect female pheromones and species-specific signals.

Define filiform antennae.

Long, slender, thread-like antennae.

Define moniliform antennae.

Antennae that look like a string of beads.

Define clavate antennae.

Antennae that are club-shaped or distinctly clubbed.

Define serrate, pectinate, and geniculate antennae.

Serrate = saw-like; Pectinate = comb-like; Geniculate = elbowed.

Define flabellate, plumose, and aristate antennae.

Flabellate = fan-shaped; Plumose = feathery; Aristate = enlarged third segment with a bristle.

What does prognathous mouthparts orientation imply?

Mouthparts oriented forward (before the mouth); often associated with active predators.

What does hypognathous mouthparts orientation imply?

Mouthparts oriented below the mouth.”

What does opisthognathous mouthparts orientation imply?

Mouthparts oriented behind the mouth; often plant-fluid feeders.

What is the mandibulate mouthparts type?

Chewing mouthparts with large, downward-oriented mandibles.

Describe haustellate (siphoning) mouthparts.

Mandibles are absent; maxillae form a long proboscis for sucking liquids.

What characterizes cutting-sponging mouthparts?

Mandibles blade-like; labium sponge-like for lapping up liquids.

What characterizes sponging mouthparts?

Mandibles reduced or absent; labium forms a sponge-like structure to soak up fluids.

Describe piercing-sucking mouthparts.

Mandibles form a piercing tool; maxillae and labium form the food canal.

Describe chewing-lapping mouthparts.

Mandibles chew; maxillae form the food canal; labium lapps or assists licking.

What are vestigial mouthparts?

Mouthparts that are largely absent or nonfunctional; adults may not feed.

What is the basic arrangement of the three head segments emphasized in the notes?

Head is composed of multiple fused parts including eyes, antennae, and mouthparts; key structures include labrum, mandibles, maxillae, and labium.

What are the three thoracic segments and how many leg pairs do they bear?

Prothorax, Mesothorax, Metathorax; each segment bears one pair of legs (three pairs total). Wings are on the mesothorax and metathorax in many insects.

What are the three main thorax sclerites per segment?

Notum (dorsal), Pleuron (lateral), Sternum (ventral). (Note: suture divides sclerites.)

What wing configurations can occur in adults?

Pterous (fully winged), Brachypterous (reduced wings), Apterous (wingless).

What is the evolutionary note about wings and flight?

Two independent wing pairs were the earliest condition; wings evolved different couplings and functions in various orders.

What is wing coupling in Lepidoptera (butterflies and moths)?

Retinaculum and frenulum mechanisms that connect forewings and hindwings for synchronized flight.

What is the term for insects with forewings hardened for protection?

Coleoptera have elytra; Orthoptera have tegmina.

What are the common flight configurations where only hindwings are used for flight approximation?

Forewings are hardened or reduced; hindwings provide the primary lift (as seen in some groups, not as a universal rule).

How many abdominal segments can be present in insects, and what is the typical segmentation?

Typically 3 to 11 abdominal segments, each with four sclerites: tergum (dorsal), pleural (lateral), sternum (ventral).

What are the ovipositor and stinger across orders?

Ovipositor is for egg deposition in many orthopterans and other orders; hymenopterans commonly have a stinger, which can also lay eggs in some species.

What are the main pros and cons of the insect exoskeleton?

Pros: prevents water loss, provides protection, supports flexibility; Cons: molting is dangerous and energetically costly, heavy in aquatic settings.

What are the major integumentary protrusions and their cellular basis?

Spines/spurs/setae; scales are modified setae; cuticular protuberances arise from trichogen, tormogen, and sensory cells.