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Late Season Laying (What Time is it in Nature)

August 24, 2016

This has been a wonderful year for butterflies at Prairie Ridge!  Their season appears to have peaked and we are now headed on a downward slope into the fall, but there is still a lot of activity happening across the grounds.  There has also been a rush for many of our butterflies to lay a few final eggs before the end of the summer.  However, because there are so many butterflies out and about, the competition for suitable egg laying locations has become intense and females have to look hard for places to lay.  Let’s take a look at a great example we came across yesterday, a Pipevine Swallowtail!

Pipevine Swallowtails are large butterflies in the swallowtail family.  They are a deep black with orange and yellow spots on the lower surface of their hindwings and a gorgeous iridescent blue on the upper surface:

pipevine swallowtail adult

Their caterpillars only feed on pipevine species, so the females lay their eggs on pipevines of a variety of species.  At Prairie Ridge, we have a large Woolly Pipevine plant growing on the fence to the right of the main entrance to the garden:

Pipevine

It’s a big plant and can support many caterpillars, but there’s a little gap between when the eggs are laid and when the caterpillars hatch.  Caterpillars can’t feed on the older, tougher leaves until they grow up a bit, so the adult females look for new growth to lay their eggs on.  That way, the newborn caterpillars will emerge right onto the softest leaves of the plant and can start feeding immediately.  As they feed and molt, they’ll become more powerful chewers and will eventually be able to eat any leaf on the plant.

At this time of year, there is a lot of new growth on our Woolly Pipevine, but there are also a lot of eggs and caterpillars already present on those parts of the plant.  If there are too many eggs laid on the soft new growth, the caterpillars might eat all of their food before they are able to chew the tougher leaves and starve.  Adult females thus look for new growth that doesn’t already have eggs or caterpillars on it.  Our Woolly Pipevine is absolutely crawling with caterpillars currently, so the females now need to look a little harder for suitable places to deposit their eggs.

That brings us to yesterday!  An adult female Pipevine Swallowtail appeared and started flying around the Wooly Pipevine on the fence.  She landed on many different parts of the plant, turning little circles on the leaves or stems where she landed and probing the plant parts with the tip of her abdomen.  (Butterflies can “taste” things with chemical sensors in their feet, so presumably she was looking for something that tasted like pipevine!)  She apparently didn’t find a good place while she was on the primary plant, so she started searching a little further out.  Eventually, she started flying around this spot on the ground near the pond in the garden:

Pipevine sprout hidden in mulch

See the plant?  If not, it’s highlighted here:

Pipevine sprout highlighted in mulch

Really, there’s a plant there!  Let’s zoom in a little further:

Pipevine sprout up close

That big piece of mulch above and to the left of the plant in the center is about 2 inches long for scale.  A very small Woolly Pipevine sprout!  However, this was apparently a good sprout, as the female “tasted” the plant extensively before settling down to lay some eggs on it:

Pipevine Swallowtail laying

She held her abdomen to the under surface of the leaves for about half a minute, then fluttered off looking for more plants.  These are her eggs:

Pipevine sprout

All that work for two little red eggs on a tiny sprout.  Hopefully they will hatch soon and we’ll be able to see some tiny caterpillars munching on slightly larger Woolly Pipevine leaves!

The butterflies will likely be very abundant at Prairie Ridge for a few more weeks.  Consider coming out soon to see how many different types you can see!   We’ve also highlighted several butterflies recently on our Prairie Ridge Facebook page, so you can find more information and photos about Prairie Ridge butterflies and other species there.

What Time is it in Nature is a periodic feature highlighting the current plants, animals, and other wildlife at the Museum’s public outdoor facility, Prairie Ridge EcostationFind out more about the natural happenings at Prairie Ridge at our What Time is it in Nature Archive.

Photos by Chris Goforth

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