Subphylum Uniramia - the centipedes, millipedes, insects, and others

(Unless otherwise noted, all photos and diagrams are from: http://biodidac.bio.uottawa.ca/)

 

 

  • This is the most diverse group in the animal kingdom - no other group even comes close!
  • most Uniramians are INSECTS! (and most insects are beetles!!!)
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    5 Classes, here are the 3 best known classes:

     

    Class Chilopoda: the centipedes

  • terrestrial predators
  • many body segments
  • 1 pair of legs per segment
  • first pair of appendages modified into poison fangs
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  • Info on house centipedes: http://www.ent.iastate.edu/ipm/iiin/housece.html
  • A nice centipede photo, and information regarding this photo: http://www.nps.gov/bibe/arthro.htm
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    Class Diplopoda: the millipedes

  • terrestrial, feeding on decaying organic matter
  • NOT close relatives of centipedes
  • many body segments, two pairs of appendages on most segments
  • some produce cyanide compounds for protection against predators
  • Some diagrams of millipedes:
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    Class Insecta: the insects

    Importance of Insects:

  • The most diverse group of animals
  • MORE SPECIES OF INSECTS THAN ALL OF THE OTHER ANIMAL GROUPS COMBINED!!!!
  • Most of these are beetles!
  • Close to a MILLION described species
  • Almost certainly another million yet to be described!
  • Almost exclusively terrestrial and freshwater
  • very few (almost none) in marine habitats (where crustaceans are the dominant arthropods)
  • Insects are extremely important:
  • Critical, major components of terrestrial and freshwater food chains/food webs
  • Play critical roles in making the world function!
  • Eaten by other animals
  • Eat other animals
  • Eat plants
  • Pollination of many wild plants
  • Recycling of detritus (insects enhance decomposition rates)
  • We depend on insects for crop pollination
  • Insects are our major competitors for food
  • Most insects are beneficial or harmless to humans, but some spread serious diseases
  • Most large universities have entire departments devoted to the study of insects (entomology)

    • Brief overview of insect anatomy and physiology:

  • 3 body segments
  • Head
  • diverse specialized mouthparts
  • one pair of antennae
  • pair of compound eyes plus extra ocelli
  • Thorax
  • 3 pairs of legs attached to thorax - 6 legs total
  • 2 pairs of wings in most adult insects (only adults have wings!)
  • Abdomen (normally with no appendages)

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  • Mouth
  • Many insects have chewing mouthparts
  • e.g. grasshopper: http://www.insectsexplained.com/img/0309.JPG
  • Many others have piercing-sucking mouthparts
  • e.g. mosquito:
  • http://www.dorlingkindersley-uk.co.uk/static/clipart/uk/dk/exp_insect/exp_insect048.jpg
  • http://www.micrographia.com/specbiol/helmint/nematod/nema0100/mo171ims.gif
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  • Compound eyes (typical of most arthropods)
  • eyes with muliple facets

  • Open circulatory system
  • Diagram of bee, showing heart (with multiple ostia) and blood vessels in red. Digestive system is in orange.

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  • Respiratory system
  • Breath through spiracles on side of abdomen
  • Air reaches cells via tracheal system
  • insect body is permeated by air tubes!
  • no cell is very far from tracheal system
  • Some insects (especially larger ones) expand and contract abdomen rhythmically to improve air exchange

    • Also see: cross section of an insect, showing tracheal system

    Photo of tracheal system in dissected Manduca sexta caterpillar

     

     

  • 2 main types of development:
  • Incomplete (gradual) metamorphosis
  • Juveniles (nymphs) look like miniature adults without wings.
  • Nymphs often have very similar lifestyles to adults, eat same food, etc.
  • e.g., grasshopper:

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    Moth

     

    Beetle

     

     

  • Flight
  • The single most remarkable thing about insects!
  • Has contributed to incredible insect success
  • exploitation of food resources
  • dispersal
  • escape from predators
  • ONLY ADULT INSECTS HAVE WINGS
  • Acquired in an individual's last molting
  • If an insect has wings, you KNOW it is an adult (even if very tiny)
  • Some adult insects are wingless
  • Some entire orders are wingless (e.g. fleas, lice, silverfish)
  • Some entire species in otherwise winged orders are wingless
  • Some individuals in some winged species are wingless
  • e.g. worker ants
  • worker and soldier termites
  • some female moths,
  • most aphids (only some indivduals in population have wings)
  • etc.
  • etc.
  • (lots of examples of this)

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    Overview of insect diversity:

  • Approx. 31 orders
  • approximate because some orders are lumped by some entomologists, split by others
  • Most orders are very common and abundant nearly everywhere
  • Most orders contain multiple families
  • Some orders contain MANY families!

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    Some of the more familiar insect orders:

    (Click here for insect links in addition to those below)

     

    Thysanura - silverfish (and others)
    (recently split into two new orders, but this old name will work for our purposes for now)

  • incomplete metamorphosis
  • wingless, with long tail-like appendages on tip of abdomen
  • chewing mouthparts
  • common household pests (eat starch on paper in books, for example and many other things)
  • Page with nice photo of silverfish
  • Silverfish info
  • Information on firebrats
  • Thysanura development
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    Ephemeroptera - mayflies

     

    Diagram of mayfly adult

    (lacks functional mouthparts and live just a few days)

  • incomplete metamorphosis
  • aquatic nymphs (most of life cycle)
  • nymphs are very cool animals
  • common in clean streams
  • some species in lakes
  • winged adults
  • brief (ephemeral) adult life, just days
  • adults lack functional mouthparts
  • mission of adults: mating, egglaying, dispersal
  • the model for many fishing flies
  • adults sometimes extremely abundant

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    Diagram of mayfly nymph (aquatic)

    (note abdominal tracheal gills on side of abdomen)

     

     

    Mayfly nymph video

    Mayfly adults emerging

     

    Odonata - dragonflies and damselflies

  • incomplete metamorphosis
  • chewing mouthparts
  • aquatic nymphs
  • Damselfly nymph - note the 3 tracheal gills at end of abdomen (dragonfly nymphs lack these and have internal gills instead):

  • Nymphs are voracious predators
  • Use hinged, extensible lower jaw to strike at and grab prey (see nice diagram at: http://media-2.web.britannica.com/eb-media/18/24018-004-C8846E21.jpg)
  • Very cool video clip of dragonfly nymph feeding behavior
  • Dragonfly nymph catching and eating fish
  • Another great video of dragonfly nymphs hunting
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  • adults are incredibly swift and agile in the air
  • adults are predators, typically of flying insects (caught in flight)


    Dragonfly adult hunting
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  • dragonflies hold wings out when at rest:
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    Dragonfly photo by W. Capman

  • damselflies fold wings back when at rest
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    A great intro to dragonflies and damselflies

    Another useful page

     

    Orthoptera - grasshoppers, katydids, and crickets

    (roaches, mantids, and walkingsticks used to be included in this order, but most biologists place them in separate orders)

  • Incomplete metamorphosis
  • Chewing mouthparts
  • Large muscular hind legs for hopping
  • Males of many species (most species?) "sing" to attract females
  • use wings (and sometimes legs) for sound production
  • grasshoppers, katydids, and crickets are generally herbivorous
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    Grasshoppers (most species active by day, court and mate during day)

     

    Katydids (typically large, green, and live on plants or up in shrubs and trees, some sing by day but many others usually do their singing at night)

     

    cool video showing katydid flying in slow motion: http://www.youtube.com/watch?v=WIovz948rYA

    recordings of the songs of various katydid species (and some cricket songs too)

    And then there's this

    Crickets (most species live on ground, sing and mate mostly at night)

    Isoptera - termites (Isoptera means "equal winged")

  • Incomplete metamorphosis
  • Chewing mouthparts
  • Sort of look like white ants, but very different from ants and not related)

    • see photo of worker termites and a winged reproducive individual

  • Feed on wood and other dead plant matter
  • cellulose is a major component of the foods termites eat
  • animals lack the enzymes necessary to digest cellulose
  • termites have symbiotic cellulose-digesting bacteria and other microorganisms in gut that allow termites to use cellulose as a food source
  • Social
  • large colonies
  • only one reproductive female (the queen) and male per colony
  • the reproductives are only termites with wings, but lose wings once they settle down and start a colony
  • in some species, queen's abdomen becomes grotesquely enlarged as she is transformed into an enormous egg factory!

    • See: http://www.ars.usda.gov/is/graphics/photos/formosan/k8085-21.htm

    https://www.youtube.com/watch?v=RAeqkQa_cuQ

    https://www.youtube.com/watch?v=xZ3pyC-s4Mg (note, despite the title of this video, termites are NOT ants!)

  • Where colonies live:
  • some species build tunnels underground, build mud tubes up to food (e.g. wood), into which they tunnel to get food.
  • some species reside within wood
  • some species (in tropics) build enormous tower-like mounds of mud (see: African termite mound)
  • VERY important globally
  • break down plant material helping to return nutrients to soil
  • swarming alates (wingd reproductive termites) are important food source for many animals (for humans too!)
  • Termites are incredibly abundant in the tropics!
  • Only one species (the subterranean termite) lives as far north as Minnesota
  • overwinters below frost line
  • not very common in MN
  • VERY common farther south
  • can destroy wooden structures

    Links to photos and more information can be found at:

    The Eastern Subterranean Termite

    • Also see

  • http://edis.ifas.ufl.edu/ig097

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    Continued on Insects, Page 2