When I was in my early teens, I used to stay overnight on Friday nights at my best friend Debbie’s house, because her mom would let us stay up late and watch really bad 1950’s horror movies (and eat huge bowls of popcorn). We binged on cringe-worthy movies like Them! (a 1954 hit about giant irradiated ants), Godzilla, World Without End (giant spiders) and Beginning of the End (featuring school-bus sized locusts).
Years later, when I read David Quammen’s 1985 Natural Acts article “Is Sex Necessary?” in Outside magazine, I was glad that aphids had never been irradiated. Of course science says it wouldn’t make them huge, but you never know 😉
Quammen’s article about virgin birth (parthogenesis) was enlightening and somewhat tongue-in-cheek. But it was the first time I’d ever thought about the reasons why some insects and other species (not mammals) might have evolved to reproduce in different ways – sexually or not. And I went and reread the article this week (in his book about Natural Acts) because I remembered the article (and have been thinking about aphids as I’ve been battling an infestation of my young osoberry tree.
Aphids (in case you didn’t know) are small, soft-bodied insects that survive by sucking sap from plants. There are over 4,000 different species in the superfamily Aphidoidea. They are successful survivors, in great part due to their methods of propagating the species. They can shift from non-sexual reproduction using a method of live births without fertilization (parthogenisis) to sexual reproduction, apparently due to changes in the availability of food or other threats to their survival.
Did you know that one single, wingless female aphid can produce so many offspring in a single summer, they could circle the earth (and a bit over) around its thickest circumference >44981.165 km!
While many creatures that reproduce this way may be either all-male or all-female. The amazing thing about aphids is that they product wingless or winged offspring that are generally female BUT with environmental factors change (food resources are too scarce), they are able to give birth to both male and female aphids that are capable of sexual reproduction.
If you’re curious (or inquisitive perhaps) take a look at the life cycle drawing from David Voegtlin:
In general, an egg is left near a food source (a leaf bud perhaps) before winter. As conditions warm and sap starts to flow, a wingless female hatches (known as fundatrices or stem mothers). She immediately burrows her head into the plant and begins feeding.
Within a week, she becomes a reproducing adult and can produce 5 offspring/day for 30 days. Each of her offspring follow the same cycle throughout the summer.
When habitat conditions or disease threaten the success of the infestation, the stem mothers produce females with wings who fly to find new food sources. The females on the new food source continue reproduction and some are born as winged males. They mate and then deposit eggs to overwinter on a chosen plant to start the life cycle again
Despite my feelings about the aphids on my osoberry tree, the more I read about their life cycles, social characteristics, anti-predator defences and that they supply ants with honeydew (that they excrete from their anus???), the more intrigued I am by this super-successful species.
Check out some of the many detailed videos about aphids on Youtube or read more about their relationships ants, etc. – I started from a Wikipedia article – https://en.wikipedia.org/wiki/Aphid