Tag Archives: Crab spider

May 3 2012

Depending on each other for survival

To eradicate alien invader plants is really hard physical work. However, it can be rewarding in other ways sometimes.

While spraying Pompom weed (Campuloclinium macrocephalum) in December 2011, I found a beautiful yellow crab spider (Thomisus sp.) on one of the Pompoms I was about to remove.  I was a bit more that 1km from home and immediately went to fetch my camera, praying that it would stay there until I come back. It was quite a hot summer’s day and I had a glass of cool drink first to quench my thirst.

When arriving back, I found that it was in the meantime successful in a hunt. It had caught a bee (Apis mellifera) and was busy sucking it dry.

Crab spider with a bee

That alone was something special, but what intrigued me most was the two little flies that joined in the feast; also sucking out the juices of the bee. The flies can possibly be Jackalflies (from the family Milichiidae).

The flies can clearly be seen in this picture

The spider and flies didn’t play on the job, it didn’t take long to finish their meal. Later that afternoon when I went to see, the bee was sucked dry and it layed on the ground.

Note the difference in the size of the abdomen of the fly between this picture and the previous one. It was taken one minute apart.

The spider remained on the flower for two more days before it disappeared and then I finished my eradicating job and removed the flower before it could spread it seeds.

A question that can be asked is: Why didn’t the bee see the yellow predator on the pink flower? The answer is easy. Bees don’t see colour the way we do. They see a broader spectrum of light than we do. Bees can detect ultraviolet light and have a completely different view of flowers than we have. The ultraviolet rays are too short for the human eye to detect. The most possible scenario is that the spider has the same ultraviolet colour as the flower, and therefor basically well camouflaged for its prey.

So how did the different species depend on each other for survival? The spider used the flower to blend in, waiting well camouflaged in ambush for the prey. The bee, although being preyed upon, possibly pollinated the flower. The fly hanged around the spider who injected a poison to liquefy the prey to enable it to feed on the bee, and then the fly could also feed. So, in this case it was only the bee who gave up its life, with three other species benefiting from its death!

Things like this makes it worthwhile to fight for the biodiversity on my farm, and I thank God for the privilege to observe these tiny little critters that otherwise would have gone unnoticed.

 For further reading about bees and how they see colour:

Other interesting reading