Strepsiptera scorpionflies and fleas
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Strepsiptera, scorpionflies and fleas. ( EE , pp. 203-217). Phylogeny of Hexapoda from p. 52. Strepsiptera. Strepsiptera. Common name: Strepsipterans (560 known world species (0.06%)) Derivation: Gk. streptos - twisted; pteron - a wing

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Strepsiptera, scorpionflies and fleas

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Strepsiptera, scorpionflies and fleas

  • (EE, pp. 203-217)

Phylogeny of


from p. 52



  • Common name: Strepsipterans (560 known world species (0.06%))

  • Derivation: Gk. streptos - twisted; pteron - a wing

  • Size: Body length 0.4-35 mm; usually under 6 mm

  • Metamorphosis: Complete (egg, larva, pupa, adult)

  • Distribution: Worldwide

  • Number of families: 8



Key Features

  • endoparasites of insects

  • rarely seen

  • sexes dimorphic

neotenous female

free living male

Strepsiptera(highly specialized endoparasites of other insects)

  • usually found in bugs, wasps and bees

  • divided into two suborders

    • in one, fully grown males and females leave the host

    • in the other, males leave the host, but females are neotenous (retaining features of the immature stages in the adult), and totally endoparasitic

Neotenous females(have no eyes, antennae, mouthparts, legs or external genetalia)

  • they do not move

  • only the cephalothorax is visible (see below)

Life cycle(females can lay about a 1000 to many hundreds of 1000s of eggs)

  • first instar larvae develop inside the female

  • females give birth to many thousands of tiny, six-legged, first instar larvae, called triungulins

  • triungulins try to find immature stages of the appropriate host

More on life-cycles(Strepsipterans require specific hosts to complete development)

  • if the hosts are exopterygotes (e.g. grasshoppers or bugs), triungulins are shed as the host moves about

  • if the hosts are social Hymenoptera, triungulins emerge when the host visits a flower - here they sit until a suitable host arrives

  • once inside their new host, they immediately molt into a legless parasite

  • when the adult male emerges, the host dies; hosts of females live until she has mated and given birth

  • Strepsiptera cause parasitic castration - their hosts cannot reproduce


  • Common name: Scorpionflies (550 known world species (0.06%))

  • Derivation: Gk. mekos - long; pteron - a wing

  • Size: Body length 3-28 mm

  • Metamorphosis: Complete (egg, larva, pupa, adult)

  • Distribution: Worldwide

  • Number of families: 9

Key Features

  • distinctive elongated face

  • mostly in damp wooded areas

  • name derived from swollen genitalia observed in some male species

bittacid - hangingfly

mostly southern hemisphere

panorpid - common scorpionfly

northern hemisphere

Mecoptera(richly veined wings make them superficially resemble neuropterans)

  • are closely related to flies (Diptera)

  • biting mouthparts

  • antennae are thread-like, with up to 60 segments (often longer than half the length of the body)

What do they eat?(most feed on dead or dying insects)

  • also feed on carrion, nectar, sap flows and fruit juice

  • some (e.g. panorpids) rob prey from orb webs

  • a few members feed on mosses (e.g. snow scorpionflies - shown to the left) and some are herbivorous

Mecoptera reproduction(usually takes place in the dark; eggs are laid in small groups in soil)

  • can involve pheromones and nuptial gifts - either a dead insect or a mass of saliva stuck to the surface of a leaf

  • males often try to wrestle other males during copulation - some will also steal nuptial gifts

  • larvae usually have compound eyes, although some are eyeless




  • Common name: Fleas (2500 known species (0.25%))

  • Derivation: Gk. siphon - pipe, tube; a+pteron - wingless

  • Size: Body length 1-8 mm; mostly under 5 mm

  • Metamorphosis: Complete (egg, larva, pupa, adult)

  • Distribution: Worldwide

  • Number of families: 16

Key Features

  • small, wingless ectoparasites on mammals and some birds

  • blood feeders

  • characteristic jumping ability

  • many species are vectors of disease

cat flea

Siphonaptera(found wherever there are suitable hosts, even Arctic and Antarctic)

  • most are parasitic on land mammals (>90%)

  • the rest are attached to birds

The flea life cycle(most fleas do not live on their hosts all the time)

Flea diversity(the largest flea family comprise more than 20% of all flea species)

  • The Ceratophyllidae (largest family) has more than 80% of its 520 species associated with small rodents, the remainder with birds

  • 120 species in the Ischnopysllidae are associated with cave dwelling bats

Fleas as pests(many species are of medical or veterinary importance)

  • bites are itchy and irritating, but they can also cause allergic reactions and transmit a variety of diseases and parasitic worms

  • The best-known disease associated with fleas is Black Death (or bubonic plague)

    • caused by a bacterium (Yersinapestis), which is primarily a disease of rodents

    • fleas pick up the bacteria during a blood meal on an infected rat

    • transmission occurs because bacteria multiple and block the midgut - infected blood is pumped back into the host

“Ring Around the Rosie”(the connection between fleas, bubonic plague and a famous nursery rhyme)

Ring around the rosies has not always been simply a playfull nursery rhyme

Ring Around the Rosie (Ring a ring o’ roses) a pocket Full of PosiesAshes, ashes (ah-tishoo, ah-tishoo)We all fall down.

In actuality, according to numerous sources, "Ring around the Rosie" describes the people of Europe who were stricken with the deadly plague. "Ring around the rosie" refers to the red ring that developed around the sores that characterized a victim of the plague.  "A pocket full of posies" was carried to cover the smell of dead, decaying bodies.  "Ashes, ashes" signify  deteriorating black lungs and the decomposing bodies of the Europeans.  And you know the rest of the story........."We all fall down".

(the letters shown in blue indicate the British version)

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