Misumena vatia is one of my favourite garden predators, lying patiently in wait on her chosen flower for any unsuspecting insect to visit in pursuit of pollen or nectar.

They are wonderful spiders to observe, with them seemingly watching you as much as you are watching them.

Star Attraction

Colourful Crabs

They are members of the Thomisidae or crab spiders, so-called after their crab-like appearance and ability to move sideways. They are characterised by having the two front pairs of legs noticeably longer than the hind pairs. The females range in colour from white through greenish to pale and then deep yellow. Often the sides of the head area (the cephalothorax) are darkened and the abdomen sometimes bears red stripes or broken lines. As well as sitting openly on a flower, these spiders also conceal themselves in amongst petals or flower spikes.

The Female is Deadlier than the Male

Females are encountered far more often than males which are considerably smaller but are just as distinctive. They are rather leggy in appearance with the first two pairs of legs very long and darkened. The abdomen is white with dark lateral stripes and the cephalothorax is dark like the legs with a lighter central area.

Patience is a Virtue

The female spider sits patiently in wait with her front two pairs of legs spread wide ready to snap shut on any prey that walks within her grasp. As well as being able to see her prey with her eight eyes, Misumena vatia (as with other species of spider) has sensitive hairs (trichobothria) on her legs with which she can detect subtle air movements enabling her to sense where her prey is.

Hide and Seek

On some flowers, the spider seems to stand out like a sore thumb but it must be remembered that their insect prey see very differently to the way we do, not least in being able to perceive ultra violet light. We cannot begin to imagine what a stationary Misumena looks like to a bee with its compound eyes.

A Varied Diet

I have observed a wide variety of insects being caught and consumed by Misumena vatia but flies and bees feature heavily. There are a number of beehives on the allotments near our home and consequently we often have lots of honeybees in the garden. These are often caught by the resident Misumena spiders which thankfully means that they aren’t always eating my favoured solitary bees!

Although they have powerful venom, the crab spiders have relatively weak jaws (chelicerae) so instead of chewing their food as they digest it with enzymes like some other spiders, they suck their victims dry leaving behind an empty husk. Very useful for an entomologist who wants to know what they have been eating!

Bitten off more than you can chew – not likely!

Misumena vatia is an extremely efficient predator, aided and abetted by fast acting venom they are able to take prey much larger than themselves. Even very small immature spiders tackle insects more than twice their size.

Variations on a theme: the different colours of Misumena vatia

As well as lying motionless in wait or concealing themselves in ambush, Misumena vatia has a further trick up her sleeve, the ability to change colour. This is rather limited it must be said and is by no means instantaneous either; it takes two or three days for the change to take place but it enables them to better blend in with a wider variety of flowers.

When a Spider is a Fly’s Best Friend…

While photographing one particular individual in the garden this year, I was surprised to spot lots of little flies crawling over the spider’s prey, a freshly caught Honeybee. These turned out to be members of the Milichiidae, sometimes called Jackal Flies. They home in on the freshly caught prey of spiders, particularly bees and wasps and true bugs, thought to be attracted by distress pheromones given off by the victim. They dine on the juices of the prey, earning the alternative name of Freeloader Flies.

With special thanks to Dr Tony Irwin for the information on ‘Jackal Flies’.