ENTM010 UCR Midterm 1 study set - FALL 2026

What morphological characteristics distinguish insects from other arthropods?

Three tagmata (head, thorax, abdomen), three pairs of jointed legs, one pair of antennae; many adults have two pairs of wings.

What is taxonomy, and what does it organize?

The science of describing, naming, and classifying organisms in a hierarchy.

What is a phylogenetic tree, and what does it show?

A diagram of hypothesized evolutionary relationships, common ancestry, and sometimes the history of traits.

Name the domain, kingdom, phylum, subphylum, and class of insects.

Eukarya; Animalia; Arthropoda; Hexapoda; Insecta.

What major traits explain the evolutionary success of insects?

Protective exoskeleton, small size, high reproduction, flight, metamorphosis, and sociality in some groups.

How do insects grow despite having a rigid exoskeleton?

They molt (ecdysis), shedding the old cuticle so a larger exoskeleton can form.

What is metamorphosis?

A developmental change in form and function between immature and adult stages.

How do larvae and adults of holometabolous insects differ ecologically?

They often occupy different habitats and eat different foods, reducing competition.

How does juvenile hormone affect the outcome of molting?

High juvenile hormone maintains immature features; lower or absent levels permit later developmental transitions.

Name and describe the three major types of insect development.

Ametabolous: little change, no pupa; hemimetabolous: egg-nymph-adult; holometabolous: egg-larva-pupa-adult.

What are the three types of insect visual organs?

Compound eyes, ocelli, and stemmata.

What are the three regions of the insect alimentary canal?

Foregut, midgut, and hindgut.

What are the main functions of the insect abdomen?

Digestion, respiration, excretion, and reproduction.

Name the main external and internal structures for insect respiration.

External spiracles and internal tracheae/tracheoles.

Name the five insect leg adaptations and their functions.

Cursorial: running; raptorial: grasping; saltatorial: jumping; natatorial: swimming; fossorial: digging.

What two major kinds of defense do plants use against insect herbivores?

Chemical defenses (toxins/deterrents) and physical defenses (spines, hairs, tough tissues).

How do specialist and generalist herbivores differ?

Specialists feed on a narrow range of related plants; generalists feed across many plant families.

What is an insect-induced gall?

An abnormal plant growth induced by insect activity that may shelter and nourish the insect.

How does feeding by sap-sucking Hemiptera differ from caterpillar and beetle feeding?

Many Hemiptera pierce plant tissues and suck fluids; caterpillars and many beetles chew plant tissue.

Which five orders include major agricultural insect pests?

Coleoptera, Diptera, Lepidoptera, Thysanoptera, and Hemiptera.

What makes an introduced species invasive?

It establishes outside its native range and causes economic, environmental, or health harm.

Name four beetle families containing wood-boring pests.

Buprestidae, Cerambycidae, Scolytidae (as named in the lecture), and Curculionidae.

What is the enemy release hypothesis?

Introduced species may flourish where effective predators or other natural enemies are absent.

What order and traditional suborder contain termites, and how do they digest wood?

Blattodea; Isoptera. Gut microbial symbionts help digest cellulose.

Why can invasive insects cause severe damage?

Rapid reproduction, broad tolerance, resource competition, enemy escape, novel niche use, and ecosystem disruption.

What insects belong to Lepidoptera?

Butterflies, moths, and skippers.

Approximately what share of described living species does the student reference attribute to insects?

About 57% (figure from the supplied student reference; not independently verified in the study guide).

What are the two major body regions commonly described in chelicerates?

Prosoma (cephalothorax) and opisthosoma (abdomen).

How many pairs of walking legs do insects and typical adult arachnids have?

Insects: three pairs; arachnids: four pairs.

What is the relationship between phenotype, genotype, and environment?

Observable phenotype reflects the interaction of genotype and environment.

True or false: heritable phenotypic variation is necessary for evolution by natural selection.

True.

Which insect order has the most described species?

Coleoptera (beetles).

Match Lepidoptera, Mantodea, and Zygentoma to developmental type.

Lepidoptera: holometabolous; Mantodea: hemimetabolous; Zygentoma: ametabolous.

What is the main structural polysaccharide of the insect exoskeleton?

Chitin.

True or false: all arthropods are insects.

False. Insects are one group within Arthropoda.

What are insect scales?

Specialized flattened setae.

True or false: centipedes and millipedes have more pairs of antennae than insects.

False. Both typically have one pair.

Why does an exoskeleton promote insect success?

It provides protection, support, muscle attachment, and a barrier to the environment.

Can tagmosis evolve within one or two individual generations?

Not generally; it describes evolutionary specialization of body regions over lineages.

What is the primary function of compound eyes?

Vision, including detection of movement.

What are the two main sensory functions of antennae?

Chemoreception and mechanoreception.

To which tagma are insect legs and wings attached?

Thorax.

How do insect hemolymph and human blood compare?

Both transport nutrients and wastes; human blood transports most respiratory gases, while insect tracheae usually do.

True or false: spiracles are part of the insect respiratory system.

True.

What is a major function of the insect hindgut?

Water and ion recovery and feces formation.

True or false: male insects produce a spermatheca.

False. The spermatheca is a female sperm-storage organ.

Which insect tagma carries antennae?

The head.

What is artificial selection?

Humans preferentially breed organisms with desired heritable traits.

What feeding damage creates tumor-like structures that may shelter insects?

Gall formation.

Which beetle family often has a conspicuous snout?

Curculionidae (weevils).

Why can agricultural monocultures encourage insect pest outbreaks?

A single crop species supplies concentrated, abundant resources for specialist herbivores.

Which insect order is known for rasping mouthparts?

Thysanoptera (thrips).

What is reciprocal selection in plant-insect coevolution?

Evolutionary change in each interacting lineage imposes selection on the other.

What is the difference between a vector and a pathogen?

A vector transmits disease; the pathogen is the causative agent.

How do a leaf miner and a wood borer differ?

Leaf miners tunnel inside leaves; wood borers tunnel inside woody or other plant structures.

What plant symptoms suggest piercing-sucking insect feeding?

Yellowing, wilting, curling, honeydew, or pathogen transmission.

What is the role of the insect fat body?

Metabolism, nutrient storage, and detoxification.

How do Malpighian tubules and the hindgut work together?

Tubules move wastes into the gut; the hindgut recovers water and ions.

What structures form the classic chewing mouthparts?

Labrum, mandibles, maxillae, labium, and hypopharynx.

How do elytra, tegmina, and hemelytra differ?

Elytra: hardened beetle forewings; tegmina: leathery forewings; hemelytra: hardened base with membranous tip.

How do the life cycles of grasshoppers and butterflies differ?

Grasshoppers develop through nymphs; butterflies pass through larva and pupa.

Why are insect wings important beyond flight itself?

They enable dispersal, escape, mate finding, and colonization of habitats.

What is the difference between the fluctuating resources and enemy release hypotheses?

Fluctuating resources: disturbance increases available resources; enemy release: fewer effective natural enemies.

What are the stages of a biological invasion?

Introduction, establishment, and potentially spread and harmful impacts.

How do termite and ant body shapes differ?

Termites have a relatively broad waist; ants have a constricted waist.

How can ambrosia beetles damage trees?

They bore galleries and introduce associated fungi, sometimes disrupting tree transport tissues.

What do xylem and phloem transport?

Xylem: water/minerals; phloem: sugars and organic nutrients.

Why can trees be hard for insect herbivores to digest?

Their cellulose-rich woody tissues are difficult to break down without symbionts.

What is integrated pest management (IPM)?

A coordinated, evidence-based approach using monitoring and multiple control methods to limit pest damage and risks.

What four major pest management options are used in IPM?

Cultural, mechanical/physical, biological, and chemical control.

How can pesticide resistance arise by natural selection?

Heritable resistant insects survive treatment and reproduce, increasing resistance frequency.

What is the difference between pollination and fertilization?

Pollination transfers pollen; fertilization is gamete fusion afterward.

Why isn't every flower-visiting insect a pollinator?

Visiting alone does not guarantee pollen transfer to a compatible stigma.

What is the pollinator significance of Apis mellifera?

The European honey bee is a major managed crop pollinator in family Apidae.

What are the families of blow flies, house flies, flesh flies, and bee flies?

Calliphoridae, Muscidae, Sarcophagidae, and Bombyliidae, respectively.

What are the families of hawk moths, swallowtails, and brush-footed butterflies?

Sphingidae, Papilionidae, and Nymphalidae, respectively.

What are the order and family of the emerald ash borer?

Coleoptera: Buprestidae.

What are the order and family of the Asian long-horned beetle?

Coleoptera: Cerambycidae.

What is the order and family of the South American palm weevil?

Coleoptera: Curculionidae.

What is the order and family of the Asian citrus psyllid?

Hemiptera: Psyllidae.

What is the order and family of the spotted lanternfly in the guide?

Hemiptera: Fulgoridae.

What is the family of leafhoppers and sharpshooters?

Cicadellidae.

What is the family of aphids?

Aphididae.

What is the family of leaf beetles?

Chrysomelidae.

What is the family of many fruit-infesting true flies?

Tephritidae.

What is the family of many cutworm moths?

Noctuidae.

What are the functions of the head, thorax, and abdomen?

Head: feeding/sensing; thorax: locomotion; abdomen: digestion, respiration, excretion, reproduction.

What is the difference between a nymph, larva, and pupa?

Nymph: immature form resembling adult; larva: feeding immature form; pupa: transformation stage.

What is the relationship between ecdysone and juvenile hormone?

Ecdysone initiates molting; juvenile hormone influences the developmental outcome.

Why is a scientific name more precise than a common name?

Its genus-species combination identifies a particular taxon under standardized naming rules.

What does monophyletic mean, and how is it different from polyphyletic?

Monophyletic includes one ancestor and all descendants; polyphyletic combines separate lineages without a natural clade.

What is the difference between mutation, gene flow, drift, and selection?

Mutation creates DNA variants; gene flow moves them; drift changes frequencies randomly; selection changes them through fitness differences.

What ecological roles do insects play besides herbivory?

Pollination, predation, parasitism/parasitoidism, and decomposition or nutrient cycling.

What are the major ecological costs and benefits of insect pollination?

Benefits include plant reproduction and crop yield; costs can include floral rewards and reliance on animal partners.

What is entomology?

The scientific study of insects.

What is science?

An iterative, evidence-based process of generating knowledge about the natural world.

What makes scientific results reproducible?

Independent researchers can repeat methods and obtain similar results.

Why can scientific explanations change?

New evidence and technology can improve or challenge existing explanations.

Why are insects important to agriculture?

Some damage crops; others pollinate crops or suppress pests.

What are ecosystem services provided by insects?

Benefits such as pollination and natural pest control.