I think I’ve already said that the jumping spiders (family Salticidae) are my absolute favourite group of spiders. As much as I like the Dictynids I’ve been observing in our agapanthus, if I was asked to pick the group that took the next biggest place in my heart I’d have to go for the crab spiders (family Thomisidae). I’ve written about these spiders before, so it you want the run down on the biology of these ’sit and wait predators read those posts, today I’m just showing off some photos of a partcularily striking crab spider I found hiding under a banana leaf in Vanuatu:
If you look closely at those enlarged “raptorial” forelegs you can see downward-facing spikes which are used to increase the spider’s grip on any creature foolhardy enought to fall within their grasp:
One of the reasons I like jumping spiders so much is they really show no fear when it comes to humans. Most spiders, despite their reputation, will run away when faced with a someone snooping around their hiding place, whereas jumping spiders very clearly eye you up as possible meal. Crab spiders aren’t quite so outgoing, but they aren’t timid either. This one got fed up with me holding its leaf up to get a photo, and decided instead to attack the camera lens then run up my arm. Whe even that approach didn’t keep the camera out if its face I got a very clear threat signal:
One day I going to run a whole set of out of focus photos of bugs attempting to attack my camera, but for now I have other work to do!
Sunday Spinelessness may have been on hiatus for Christmas and the New Year but the spineless themselves don’t observe holidays. During my break in the sunny Wairarapa I’ve been keeping and eye, and a couple of lenses, on some of the backyard bugs and if I was to say one thing about them it would be that they are hungry
Take the Sidymella crab spiders (previously featured on these pages) hiding in the Christmas Lilies and in particular on dahlia flowers:
On a sunny morning you can usually find one of these tiny spiders on every second flower. It took me some time to work out what was keeping all these spiders the fed. The flowers two most frequent visitors, ants and bumblebees, don’t prompt so much as a twitch from those elongated font legs. It wasn’t until Christmas day that I found my answer. Fill to the brim with my own Christmas lunch I wandered down to the back garden and saw a Sidymella tucking into its own meal – a small nectar eating fly whose taxonomic position I couldn’t guess at.
Having found at least one of the items on the crab spiders’ menu it became clear the fly is pretty common too. It’s no surprise that the bright yellow dahlias are one if the flies favourite haunts.
Last month we heard about the worlds only known vegetarian spider – a remarkable discovery given the lengths to which the other 40 000 described species go to make animals into meals. There are the familiar web builders from the family Aranediae, active hunders like jumping spiders, the ambush hunting trapdoors and tarantulas and even the bolas spiders which produce a pheromone to attract moths so they can cast a sticky trap at them and, having caught them, draw them in like fish on a line. The subject of todays Sunday Spinelessness are the crab spiders, a family (Thomisidae) of ambush predators that use camouflage and a good deal of patience to get themselves fed.
The crab spiders get their name their name from those elongated front legs which are used to seize and hold on to their pray and from their tendency to scuttle about when disturbed. Most of the larger species, like the two above, hang out inside flowers waiting for would-be pollinators to get close enough for the spider to pounce. In fact, some crab spiders might even mimic the nectar guides of flowers to increase the rate that insects visit their flowers.
Some of the smaller crab spiders like the really tiny one above (probably from the consonant deficient genus Diaea) also hang out in flowers but others hide in the joins of bark, in the leaf litter or, like this one, in fronds of herbaceous plants. I’m not quite as patient as a crab spider so I don’t have any photos of them in action but, as ever David Attenborough has a video on the topic:
