Entognatha, Apterygota & Hemimetabolous Orders Flashcards

Hexapoda

• Hexapoda includes insects (Class Insecta) and three other groups: springtails (collembolans), diplurans, and proturans.

• Non-insect hexapods are called entognathous hexapods (Class Entognatha).These groups are characterized by their unique mouthparts, which are hidden within the head, differentiating them from insects that possess exposed mouthparts. The entognathous hexapods encompass three main orders: Collembola (springtails), Diplura (diplurans), and Protura (proturans), each exhibiting distinct morphological and ecological traits that contribute to their survival in diverse habitats.

Entognatha

• Entognatha: Mouthparts are concealed within the head capsule (Ento – inside; gnatha - jaw).

• Group of ametabolous hexapods.

• Mouthparts are entognathous.

• Wingless.

• Various methods of indirect sperm transfer.

• Three Groups:

  1. Collembola (springtails)

  2. Diplura (forked tails)

  3. Protura (coneheads)

Collembola (Springtails)

• They have primitive compound eyes and one pair of antennae. They live in moist soil, under bark, and in freshwater ponds, and they tend to occur in dense populations. They possess a furcula (jumping fork) and a collophore.

Collembola Reproduction

• Unique reproduction strategy with indirect sperm transfer.

• Male deposits a spermatophore in front of the female.

• The female picks up the spermatophore.

Diplura

• Narrow, elongate body, usually colorless.

• Lacks eyes.

• Have 2 abdominal cerci.

• Name from Greek words, “dipl” (two), “ura” (tail).

• Similar to collembolans, they use indirect sperm transfer (spermatophore in the environment).

• Can be herbivorous or predatory.

Protura

• Very small (about 1mm long).

• Name implies primitive physical features: “Proto” (first, original), “ura” (tail).

• Lacks antennae (unique among hexapods).

• First pair of legs are sensory.

• Eyes absent.

• Live in moist soil.

• Detritivores.

Class Insecta

• Subclass Apterygota (no wings).

• Subclass Pterygota (winged, or descendants of winged insects): >99.9% of all insects.

Subclass Apterygota (within Class Insecta)

• Two orders of insects:

  1. Zygentoma (silverfish and firebrats)

  2. Archaeognatha (bristletails)

• “Wingless”.

• Ametabolous development.

• Long, paired abdominal cerci and a single median, tail-like caudal filament.

• Compound eyes.

Silverfish (Order Zygentoma) - Lepisma saccharina L.

• Found in decaying vegetation.

• Can be household pests.

• Indirect sperm transfer.

• Consume matter containing polysaccharides, such as starches and dextrins in adhesives.

• Some silverfish live inside of ant nests, probably scavenging the seeds collected by ants.

Archaeognatha (Jumping Bristletail)

Hemimetabolous Orders

• Incomplete metamorphosis.

• Includes:

  • Ephemeroptera

  • Odonata

  • Plecoptera

  • Dermaptera

  • Phasmida

  • Orthoptera

Ephemeroptera

• Mayflies.

• "Ephemera" meaning “existing for a short time” and pteron meaning “wing”.

• Adults are short-lived, do not feed, only disperse, mate, and die.

• Large triangular front wings.

• 1 median caudal filament and two cerci (long).

• Adults terrestrial, nymphs aquatic.
  *Nymphs respire through abdominal gills.

• Relatively long life cycles - live as nymphs for months to years.

• Have a Subimago stage—final stage before molting to adult (imago).

• Emergence swarms.

• Very important in food webs.

• The largest emergence events in Lake Erie can result in a flux of up to 87.9 billion mayflies (3,079 tons of biomass) across the water–air interface in a single night.

• Declines in an abundant aquatic insect, the burrowing mayfly, across major North American waterways.

Odonata

• Dragonflies and damselflies.

• “Toothed jaw”.

• Large, many-veined, membranous wings.

• Chewing mouthparts in adults & nymphs.

• Adult cerci function as claspers while mating (male).

• Adults terrestrial, nymphs aquatic with rectal gill pads.

• Dragonflies have wings broad at the base and held horizontally at rest.

• Damselflies have wings narrow at the base and held over the back at rest.

• Dragonfly Nymph- No External Gills

• Damselfly Nymph- Has External Gills

• Excellent predators; "mosquito" killers.

• Immature forms (nymphs) have extensible modified labium for prey capture

• Males deposit sperm into a pouch on their abdomen located near the thorax, and the female receives the sperm from the pouch.

Plecoptera

• Stoneflies.

• plekein = to fold; -pteron = wing
  *Nymphs are aquatic, prefer clean, cold water.

• Grazers or predators.

• Nymphs of most stoneflies are sensitive to water pollution and their presence is a reliable indicator of excellent water quality.

Dermaptera

• Earwigs.

• derma = skin; -ptera = wing

• Chewing mouthparts.

• Short leathery forewings.

• Large cerci on abdomen.

• Maternal Care of Eggs

  • Subsocial insects with maternal care of brood.

  • Females clean and re-pile the eggs, tending increases survival rate.
    *Chemical defense

  • first revolves the abdomen to bring the pincers to bear upon the attacker… it automatically aims the glands, so that … inevitably targets the body site under assault..

Phasmida

• Walking sticks and leaf insects.

• phasma = phantom or cryptic ghost

• Chewing mouthparts.

• Experts at crypsis.

• Capitulum: a swollen, fatty extension of the stick insect egg

Orthoptera

• Grasshoppers, Katydids, Crickets.

• ortho- = straight; -ptera = wing

• Front wings: tegmina.

• Short or long antennae.

• Saltatorial hind legs common.

• Divided into two suborders:

  • Ensifera: Elongated, thread-like long antennae (katydids, crickets, etc.)

  • Caelifera: Short antennae (grasshoppers, locusts, etc.)

• Some common families include:

  • Acrididae: grasshoppers, locusts

  • Tettigoniidae: katydids

  • Gryllidae: crickets

  • Gryllotalpidae: mole crickets

• Orthopterans make sounds by “stridulation” - rubbing body parts

  • Grasshoppers stridulate by rubbing hind legs against the edge of closed wings

  • Katydids and crickets stridulate with the wings only.

  • A sharp edge or “scraper” on the the lower wing is rubbed against a “file” on the underside of the other wing

• The use of sound is generally crucial in courtship, and most species have distinct songs

  • Tympanal organ in katydid and cricket: front tibia

  • Tympanal organ in grasshopper: first abdominal segment
    *Locusts: the swarming phase of some grasshoppers

  • Mechanics of Swarming:

    • Normally solitary

    • Transition phase with overcrowding