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Monday, April 20, 2015

Lurker in the lily

On Sunday, we were enjoying the variation in Calochortus tolmiei, moving from flower to flower, pausing at each one, looking down and wondering what pattern we would see.

I heard Peter say that I had to come over to photograph one.  I didn't know that he had found something lurking inside the lily!

That's a somewhat scary view of a crab spider, Misumena vatia scary if you're potential prey, such as a bee or a fly.

At one point I was on the other side of the flower and the spider was moving around on the petal, so the next picture shows a nice view of the spider from above:

I was intrigued to see this spider "in white."  I have seen this species in Bodega Bay before, but previously it was predominantly yellow.  We wondered if white forms were more common on white flowers?

We looked around at more flowers and spotted this next:

Hmmm...a bright yellow crab spider in a lily!  So they're not always white when lurking in these lilies.  Next I thought perhaps the color didn't matter and maybe both strategies would work, i.e., a spider could be cryptic in different ways white like the lily, or yellow like the center of a "generic flower," e.g., the Blue-eyed Grass in the background of the picture above.

Doing more research at home tonight I learned some things that made me think about this again.

The spiders can change color!  They're typically white, but when on a yellow substrate they're triggered to release a yellow pigment and then become yellow.  When on a white substrate, the yellow pigment is moved below the surface or degrades, and then the spider looks white again.  [Interestingly, it takes longer to turn yellow (10-25 days) than to turn white (only 6 days).]

Another study found that insects may see this whole scene differently than we do.  It turns out that what we see as a cryptic pairing (white spider on white flower) may really stand out to an insect.  Researchers found that a white crab spider camouflaged on a white daisy was highly conspicuous to honeybees sensitive to ultraviolet light.  And even though a predator was lurking, the bees still visited the flowers because they were attracted to high contrast color patterns!

One more interesting picture to share with you tonight:

Yes!  That's a small crab spider holding onto prey at the base of the lily.  I think the prey might be a syrphid fly, also known as a hoverfly or flower fly.  You can see the yellow-brown legs of the fly below its abdomen, and at least two legs of the spider (lighter yellow) held up above the abdomen and the wing of the fly.

P.S.  The ultraviolet light research mentioned above is from Heiling, A.M., M.E. Herberstein, and L. Chittka. 2003.  Crab-spiders manipulate flower signals.  Nature 421: 334.

1 comment:

Anonymous said...

Thank you for sharing these amazing photos of this amazing discovery. You've opened my eyes and understanding to this incredible action.