Thursday, November 19, 2009

A Look into a Tiny World: a Follow-up

I've been anticipating Jerry Powell's lecture at the California Native Plant Society's November meeting since I heard about it.  His talk about micro-Lepidoptera made me realize how much is really going on out there.  Tiny leaf miners, rappelling themselves from the leaves onto the ground and emerging as minuscule moths, many never eat a thing after they've metamorphosed. 
One thing I found incredibly interesting was the fact that most species are host specific, or in English:  they only eat one specific kind of plant.  It's made me rethink my plantings so that I'll have more host plants instead of all nectar plants.  Also, the larger the plant (such as oak trees), the more species will use that plant as a host.  While these insects may cause a little mar in a leaf here or there, they will not harm the life of the plant.  It's amazing how nature has it all figured out. 
Until, of course you get us involved.  That's right, human involvement.  Apparently, Swallowtail butterflies that use the European Sweet Fennel plant as a host have become dependent on this invasive weed and it allows them to hatch in more than one season.  They're thriving off of our mistakes.  What a dilemma!  Remove an invasive plant or save the Swallowtail?  As Steve, my favorite naturalist says, "Humans.  Ruin.  Everything."


  1. It is so interesting how seemingly small choices we humans make, have such a great impact on nature. I think many gardeners make the mistake of only including nectar plants for butterflies since they are usually more showy. But, I like your point that you need to include host plants for the caterpillars.

  2. Yes, I was so surprised that many insects don't eat once they've metamorphosed. Poor things starve themselves!

  3. i just read a fascinating book, 'Bring Nature Home' by Douglas W. Tallamy. it is well written and a fast read. he addresses exactly this issue of insects frequently eating only one type of native plant. rarely do they cross over to alien/non native plants. the swallowtail and European Sweet Fennel alignment is a rare exception. he makes a solid argument for incorporating more natives just for this reason alone. native birds are dependent on insects to raise their young and the lack of insects due to a lack of native plants supporting insects impacts the bird populations.

  4. I think Town Mouse posted a review of that book! I remember someone at the lecture asked about sweet fennel in that she wanted to eradicate it, but saw swallowtail larvae eating it. Pull it out and keep the plant population native or kill the butterflies' food? Dr. Powell's answer was interesting- since the introduction of sweet fennel, the swallowtail population boomed, allowing them to reproduce more than once a year. I guess you have to pick your battles.