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#30: Aphids


Litinsects #30: Aphids

This one’s a bit longer but I promise it’s really interesting!

Ok, I know for gardeners and plant-lovers the general consensus on aphids is probably that you hate them. They are hugely destructive pests... Unfortunately they don’t only cause damage by sucking fluids from plants but they are vectors for various plant diseases and their honeydew (more info on that below) is often a sticky mess on plants that then attracts mold.

All in all there probably aren’t many aphid fans out there. But there are honestly such cool things going on with aphid biology that make them unique and truly fascinating!

  • Most aphids are easily recognized by their CORNICLES, two tube-like protrusions from their abdomen. When threatened, they excrete a defensive substance called cornicle wax out of these tubes
  • Aphids are often wingless... but when food is in short supply, when a plant becomes overcrowded, or even in the presence of predators, aphids can produce winged, or ALATE, offspring that have the ability to disperse to other plants
  • Aphids feed on plant sap, which brings me to the honeydew I mentioned... Plant sap has incredibly high concentrations of sugar so aphids have to actually get rid of some of it. These excess sugars accumulate in the aphid‘s digestive tract (along with waste products) and are secreted as droplets out of the anus. These sugary secretions are important food sources for other animals and some ants even „farm“ aphids for their honeydew! (And yes, you read that right, it comes out their rear ends)
  • Because their diet lacks certain essential amino acids, aphids have BACTERIAL ENDOSYMBIONTS living inside them that help produce amino acids (and also help in other ways)
  • Some aphid species can produce CAROTENOIDS (the red/orange pigments responsible for the color of carrots, flamingos, tomatoes, lobster, etc.). This is possible due to an extremely rare GENE TRANSFER from fungi! Only two other animal species (a mite and a hornet) have acquired this ability, all other animals must extract carotenoids from their food
  • Aphids can reproduce asexually through PARTHENOGENESIS, in which a female essentially produces clones of herself. Aphids usually alternate between sexual and asexual generations but there are some external factors that also contribute to this. There is no known species of aphid that reproduces through sexual reproduction alone
  • Parthenogenic aphids are VIVIPAROUS, meaning they give birth to live young instead of laying eggs! Pretty crazy...
  • But that’s not all! The daughters born by parthenogenesis already have parthenogenically developing embryos inside them so they are technically BORN PREGNANT! This is known as TELESCOPING OF GENERATIONS
  • Mothers that parthenogenically produce sexual offspring (usually around autumn) produce males that are genetically identical to their mothers except for lacking one sex chromosome, which is responsible for sex determination. (They can also control offspring sex ratio). The sexual generation, usually winged, flies to a different plant, mates, and lays eggs that overwinter and hatch in the spring

So even though you might continue to hate them because of the destruction they cause your plants, I hope you can at least begrudgingly agree that they’re seriously fascinating in a lot of ways! Ok, nerd rant over for the time being 🤓

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