I am indebted to Tone Killick, one of the administrators of the UK Spider Identification Facebook page, who produced a very interesting paper on this fascinating spider. He is unconvinced about the possibility that the change in colour is to evade predators – this is a very speedy spider, and furthermore birds are able to spot the arachnid even if it’s perfectly matched to its flower. And we already know that it doesn’t apparently help the spider to catch prey. The spider has a very low rate of success (apparently it only catches 3.5% of the prey that it attempts to grab in its spikey front legs), which means that it has to wait around on a flower for a very, very long time before it gets a meal. And here’s where Killick makes an interesting lateral link. The yellow pigmentation is caused by a chemical called ommochrome, which has been shown to provide protection against UV damage in spider’s eyes. Could it be that, if a spider spends a long time in sunshine, she develops the yellow colouration as a sun screen (we could hypothesise that spiders that stay white live in shadier places). Clearly more research is needed, but for now let’s move on to the other interesting facet of the spider’s life, reproduction.
All of these biggish yellow and white spiders are female. The males are only 3-4 mm long, while the females are 9-11mm. Furthermore, the males look completely different.
In the spring, the tiny males run through the flowers following the silken threads that the females leave as they move from one bloom to another. Upon finding a female, they scramble onto her abdomen while the female continues to go about her business, seemingly oblivious.
The male then taps on the female to see if she’s receptive to some sperm transfer (like you do) and if all goes well, they mate. The male then makes an extremely speedy retreat, before he ends up as dinner. He must keep all eight legs crossed that the female hasn’t already copulated, as if so she can be extremely (life-threateningly) grumpy.
The female lays 150-400 eggs on a suitable leaf and covers it with lots of silk. Then she starts her guard duties – during this time, the only way she will eat is if a particularly silly fly blunders into her space and she can grab it. After 25 days the spiderlings hatch, and many will fly away by standing on some vegetation and holding a strand of silk which will act as a parachute. Alas, many dangers await these tiny spiders, though they can survive the freezing temperatures at 5 km above the earth’s surface. Many will be eaten by predators, and others will end up in an unsuitable environment. Some, however, will survive to adulthood, to delight amateur arachnologists and lovers of the unexpected everywhere.
I am so pleased that you have returned to this fascinating spider!
I have many of these in my garden and I didn’t know the males were so tiny! I’ll have to watch out for them to have a look.
I recall seeing some of these spiders on my travels (aka walks). I think they were usually white. Fascinating stuff. Thanks for sharing. 👍😀
Robert Frost wrote a sonnet called ‘Design’ about the colour white, which becomes sinister because a white spider has caught a white moth by choosing, he implies, to sit on a white flower that is normally blue.
Haven’t done the poem justice: it is worth seeking out.
And seek it out I have….:-0
They look like little cuties, though clearly can be ferocious!