Friday, July 20, 2012

The Colour of Nightmares: Goldenrod Triptych

An unhinged triptych of trophic interactions
Goldenrod (Solidago spp.) in bloom, a cornucopia for the Home Bug Garden arthropods, always makes me feel a little sad but less sodden: the floods and hail of summer will soon be sliding into the green tomatoes and frosts of September. Still, it is cheering to see a dozen or more different species feeding on and at the goldenrod on a sunny summer afternoon. Pollen and nectar are the major attractions, but the Goldenrod Crab Spider Misumena vatia (Clerck, 1757) is there to feast on visitors like the unfortunate Striped Hairstreak Satyrium liparops (Le Conte, 1833) above.
Striped Hairstreak in happier times looking a bit brown
I suppose, technically, the Striped Hairstreak is a pest - its larvae will feed on cherry leaves, buds, and young fruit. But it is never very common and a few cherries are a small price to pay for such a pretty little butterfly.
Same hairstreak looking more lilac
This hairstreak seems to vary in colour from moment to moment from rather brownish underneath to a more purplish hue, depending on how the light is reflected from the scales on its wings. But its nemesis is the real colour artist, changing its pigment chemistry when it chooses a yellow flower as a lair.
Goldenrod Crab Spider in its natural hue
The yellow colour change of the Goldenrod Crab Spider takes several days to accomplish, so it probably started on a nearby Heliopsis helianthoides that began blooming a week ago.
Male Goldenrod Crab Spider
Males of the crab spider are smaller, darker, and don't seem to indulge in colour change. Possibly this is because a peripatetic lifestyle, wandering from flower to flower in search of females, precludes spending much time on any one flower.
Phalangium opilio Linnaeus, 1758
The third member of our unhinged triptych is a well-travelled harvestman. Although some people seem to find these daddy-long-legs creepy, they are harmless to butterflies and to people. They feed on small insects, pollen, and dead things. I suppose the one at the top may be dreaming of cold butterfly corpse for dinner, a fitting end to our food web.


Defrize J, Théry M, Casas J. 2010. Background colour matching by a crab spider in the field: a community sensory ecology perspective. Journal of Experimental Biology 213: 1425-1435.
Defrize J, Lazzari CR, Warrant E, Casas J. 2011. Spectral sensitivity of a colourchanging spider. Journal of Insect Physiology 57: 508-513.
Insausti TC, Defrize J, Lazzari CR Casas J. 2012. Visual fields and eye morphology support color vision in a color-changing crab-spider. Arthropod Structure & Development 41: 155-163.
Riou M, Christidès J-P. 2010. Cryptic Color Change in a Crab Spider (Misumena vatia): Identification and Quantification of Precursors and Ommochrome Pigments by HPLC. Journal of Chemical Ecology 36:412–423.

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