golden days

Until this week, most of the wildflowers around the farm have been white. Consequently, most of the Misumena vatia spiders I’ve been seeing have also been white. However, that has begun to change now that the Black-eyed Susans (Rudbeckia hirta) are in bloom. This week, I’ve been finding yellow phase spiders – those that have moved from white to yellow flowers and have undergone the process of changing colour (click on photos for larger view). As you may recall from one of my earlier posts about these spiders, the process is fairly gradual. I found this brief explanation of the process on wikipedia, referenced to a paper by Oxford, G.S. & Gillespie, R.G. (1998). It states:

The color change is made possible by secreting a liquid yellow pigment into the outer cell layer of the body. On a white base, this pigment is transported into lower layers, so that inner glands, filled with white guanin, become visible. If the spider dwells longer on a white plant, the yellow pigment is often excreted. It will then take the spider much longer to change to yellow, because it will have to produce the yellow pigment first. The color change is induced by visual feedback; spiders with painted eyes were found to have lost this ability.
The color change from white to yellow takes between 10 to 25 days, the reverse about six days. The yellow pigments have been identified as kynurenine and 3-hydroxykynurenine

In addition to seeing the first of the yellow-phase Misumena vatia of the season, I found an interesting individual hunting among the leaves of the Black Walnut tree in the garden. This is the first time I’ve found one of these spiders hunting in a large tree, although I did find one hunting from a Red Oak sapling last year. As you can see from the above photo, this spider is still in its white phase, and not likely to begin changing colour unless she moves to a yellow flower. Also of interest, is that this spider has a strange marking on one side of her cephalothorax (see below — that’s the largest sized view that I have). After studying photos shot from several angles, it appears that this might be a scar of some kind as the tissue seems to be damaged and slightly deformed in addition to the mark. That’s the first time I’ve seen such a thing on one of these spiders. Today, I’ll write up some notes on these spider observations and post them to Spider WebWatch. If you’re seeing Misumena vatia around your garden, I encourage you to submit your observations too.

Tags: , , ,

  • Both comments and trackbacks are currently closed.
  • Trackback URI:
  • Comments RSS 2.0

4 Responses to “golden days”

  1. robin andrea Says:

    I love these yellow crab spiders. The ones I’ve seen here don’t have the red on them. I photographed one on Saturday that I thought of sending to you. Just a lovely bright yellow.

  2. bev Says:

    robin – yes, do send the photo along and I’ll take a look at it. It may have not markings if it’s an immature spider, but there are some other yellow species and might be one of those.

  3. DougT Says:

    I have a love/hate relationship with crab spiders. They are beautiful, and important parts of the ecosystems that they are found in. On the other hand, it’s always disheartening to find one of the endangered species of butterflies that I am trying to restore, only to notice that it’s in the clutches of a crab spider. This has happened more than once. A colleague once released several adults onto a restoration site and saw one of them get nabbed within seconds of its release.

  4. bev Says:

    Doug – I have just about the same relationship with the spiders here at the farm. Last year, I felt quite annoyed with the Argiope aurantia spiders in the “Spider Ranch” part of our gardens after I found a Hummingbird Clearwing moth wrapped in silk in the middle of one of their orbs. Crab spiders are so efficient and choose the most attractive places to hang out, so they do catch a lot of butterflies and moths.