Entomology Part 4 — Taxonomy and Nomenclature: Key Concepts and Changes

Overview of the Course and Core Themes

  • Part four provides a broad overview of entomology, focusing on insect anatomy, physiology (briefly, next weeks), evolution, taxonomy, behavior, and ecological importance.
  • Throughout the semester: discuss human relevance of insects, ecological roles, and communication within the scientific community about insect diversity.
  • Emphasis on learning both scientific names (binomial nomenclature) and common names to facilitate clear communication across languages and communities.

Binomial Nomenclature and the Linnaean System

  • Binomial nomenclature is the Linnaean system used to give every known species a unique genus + species combination.
  • Carl Linnaeus (Carolus Linnaeus), a Swedish naturalist, invented this system; his work laid the foundation for modern biological nomenclature.
  • The scientific name consists of two parts: genus name and species name. For insects, the format is: Genus species (and sometimes subspecies).
  • Examples:
    • European honeybee: Apis mellifera mellifera (subspecies included) — genus Apis, species mellifera, subspecies mellifera.
    • Black widow spider: Latrodectus mactans (Fabricius) — genus Latrodectus, species mactans; author Fabricius originally described the species (name in parentheses indicates a change in genus since the original description).
  • Formatting rules when typing vs handwriting:
    • Typing: italicize genus and species names, e.g., Apis mellifera mellifera; the author name (e.g., Linnaeus, Fabricius) is not italicized.
    • Handwriting: underline the entire binomial name (e.g., Latrodectus mactans).
  • Authorship conventions:
    • The name following the scientific name is the authority who first described the species; if the authority’s name is in parentheses, the species was originally described under a different genus.
    • Example: Latrodectus mactans (Fabricius) indicates Fabricius named the species, but under a different genus at the time.
  • Written form of authors when naming:
    • Linnaeus (capitalized, not italicized) credited for the original naming of many species.
    • Fabricius is shown in parentheses to indicate the original description under a different genus.
  • Subspecies:
    • Some domesticated or widely studied insects have subspecies. Example: Apis mellifera mellifera denotes the European honeybee subspecies.

Capitalization and Formatting Rules for Scientific Names vs Common Names

  • Proper nouns are capitalized; common nouns are not.
  • Genus names are capitalized; species names are lowercase; both are italicized when typed.
  • Domain, kingdom, phylum, class, order, family, genus, and species (the Linnaean ranks) are capitalized for the rank name (e.g., Coleoptera is capitalized as a proper taxonomic name).
  • Examples of formatting and capitalization:
    • Coleoptera (order) with capital C.
    • Chrysomelidae (family) with capital C.
    • Common names are not capitalized unless they begin with a proper noun.
    • Emerald ash borer: common name is lowercase (emerald, ash, borer not capitalized) because these are not proper nouns.
    • Monarch butterfly: common name is not capitalized (monarch butterfly).
  • Common names as clues to taxonomy:
    • One-word common names often reflect a single taxonomic group (e.g., dragonfly, firefly).
    • Two-word common names may indicate it is a composite or broader group (e.g., pubic lice, bed bug).
    • Exceptions where common names are one word despite structure: honey bee and bumblebee (usually written as one word per convention, though they describe bees).
  • The formal common-name conventions can sometimes hint at taxonomy, but they are not reliable on their own for precise classification.

Taxonomy and Non-Linnaean Rankings

  • Taxonomy is a dynamic discipline; names and groupings can change as new data emerge.
  • Linnaean rankings include domain, kingdom, phylum, class, order, family, genus, and species. There are mnemonics to remember the order, but the practical utility of full ranking decreases over time as we refine classifications.
  • Domains emphasize three broad categories of life: ext{Domains} = \{ ext{Eukarya}, ext{Bacteria}, ext{Archaea} \} and note that everything eukaryotic (animals, plants, fungi, etc.) belongs to the Eukarya domain.
  • Non-Linnaean rankings fill in gaps between the major Linnaean ranks and are not part of Linnaeus’ original system. They include: suborder, superfamily, epi-family, subfamily, tribe, etc.
  • Within any order or family, there may be additional ranks such as suborders, superfamilies, subfamilies, etc., but not all insects have every rank.
  • These non-Linnaean rankings are useful supplementary categories that help organize diversity when finer resolution is needed.

Examples to Illustrate Nomenclature and Taxonomy

  • Example 1 (binomial nomenclature with subspecies):
    • Apis mellifera mellifera (Linnaeus) — European honeybee (subspecies as listed).
    • Genus capitalized; species and subspecies lowercase; author Linnaeus not in italics; genus/species in italics.
  • Example 2 (authorship in parentheses):
    • Latrodectus mactans (Fabricius) — black widow spider; original genus assignment by Fabricius later revised.
  • Example 3 (common-name hints at taxonomy):
    • Dragonfly (one word) vs. bee fly (two words; a fly, not a bee).
    • Firefly (one word; beetle), Pubic lice (two words; louse), Bed bug (two words; true bug).
  • Example 4 (proper capitalization rules for taxa):
    • Coleoptera (order; capital C).
    • Chrysomelidae (family; capital C).
    • Common name: chrysomellid (lowercase when used as a common name).

Taxonomy Over Time: Changes, Debates, and How to Handle Them

  • Taxonomy changes as a normal part of science: hypotheses are tested and revised with new data.
  • Historical shifts can be frustrating (e.g., order Homoptera previously treated as a distinct group but later found non-monophyletic).
    • Homoptera is not a monophyletic group; modern analyses group those taxa differently.
  • Arthropod relationships: early views placed insects as sister to myriapods (millipedes and centipedes). Modern data place insects as more closely related to crustaceans, prompting a revision of phylogeny.
  • Examples of reclassification across time:
    • Lice (order Thiraptura) were once separate but later placed differently or removed as a separate order; some lice moved into other groups.
    • Isoptera (termites) historically treated as their own order; molecular data show termites are more closely related to cockroaches (order Blattodea); thus Isoptera is largely not used as a formal order in modern classifications.
  • Linguistic and educational implications:
    • Many professionals and students still use old terms due to tradition, literature, and audience familiarity.
    • It’s important to acknowledge older nomenclature while using updated classifications in scientific communication.
  • Philosophical perspective on taxonomy:
    • Biology resists binary true/false classifications; there are gray areas and varying opinions (lumpers vs splitters).
    • Lumpers favor broader, fewer taxa; splitters favor more refined, numerous taxa based on observed differences.
    • The choice between lumping and splitting affects cognitive load for learners and practical communication in field work and education.
  • Implications for practice and teaching:
    • When presenting to diverse audiences, address older names and explain current understanding.
    • Embrace the scientific method: be willing to revise hypotheses as new evidence emerges.
    • Historical context and modern data both matter for a complete understanding of entomology and taxonomy.

Practical and Ethical Implications for Study and Communication

  • Accurate naming improves cross-language and cross-cultural communication; common names can be misleading without scientific names.
  • Taxonomic changes reflect deeper insights (e.g., molecular data reshaping arthropod relationships), guiding conservation, ecological research, and pest management.
  • The balance between historical terms and updated nomenclature is necessary for effective outreach, education, and collaboration across generations of scientists.
  • The scientific method drives updates in classification; acknowledging this process helps students become flexible thinkers and better communicators.

Quick Reference Formulas and Key Points

  • Scientific name composition:
    • ext{Scientific name} = ext{Genus} \, + \, ext{Species}
  • Domain composition:
    • ext{Domains} = \{ ext{Eukarya}, ext{Bacteria}, ext{Archaea} \}
  • Linnaean rank order (from broad to specific):
    • ext{Domain} \rightarrow \text{Kingdom} \rightarrow \text{Phylum} \rightarrow \text{Class} \rightarrow \text{Order} \rightarrow \text{Family} \rightarrow \text{Genus} \rightarrow \text{Species}
  • Formatting rules (typography): genus and species are italicized; genus capitalized; species lowercase; author names not italicized; parentheses indicate original genus.
  • Common-name conventions (illustrative, not absolute):
    • Dragonfly (one word; not literally a dragon or a fly)
    • Firefly (one word; a beetle)
    • Bee fly (two words; a fly, not a bee)
    • Pubic lice (two words; a louse)
    • Bed bug (two words; a true bug)
    • Honey bee and bumblebee (typically written as one word; exceptions to the general two-word rule)

End of notes.