Yeah, crab spiders can be difficult, especially the babies! Someone has already suggested genus Mecaphesa for an ID, which is probably correct (I certainly find a lot of little yellow immatures of that genus), but I haven’t agreed to the ID yet as there are other yellow genera (such as Misumessus) in the area.
This field had a lot of bright yellow goldenrod that would have worked perfectly for this spider. Someone did suggest to me that it was trying to look like the yellow center to a purple flower…
The white and yellow ones can actually change their colour to match the flower they’re on - the catch is that it takes at least a week for them to switch from yellow to white or the reverse, so they have to stay put.
By chance I was watching an old Attenborough programme yesterday: Life in the Undergrowth (highly recommended). There was a section where he discussed these crab spiders. There were two points that he made about their camouflage that aren’t necessarily intuitive.
Firstly, the animals they prey on don’t have the same vision we have, so what we see will be different to their prey. The example given was honey bees who, in addition to the range of colours we see, have ultraviolet sight. They mocked-up how the spiders would appear to the bees, and the plain white on white the we sometimes get didn’t occur. The spiders always stood out.
Secondly, and more bizarrely, it was the spiders who could be seen more clearly by the bees that seem to have the highest success rate. It’s not camouflage that enables the kill, but being seen. I’m not sure that the reasons for this were fully explained, but there was a suggestion that it’s spiders who look the most attractive in the same way that the flowers look attractive that get the hits.
Looking at your picture, maybe we can get a feel for this. The spider looking like the flower’s pistil, its stretched out legs looking like stamen. I think your spider is acting as a lure, rather than trying to be unseen.
Very good points! Thank you for sharing them. I wonder though about the spiders predators like birds. Does it’s prey alluring color make it more visible to it’s potential predators?
Also I wonder how well they are seen by predatory and parasitic wasps. I feel like wasp interaction is the of the biggest selective pressures on spiders.
