Be careful when you stop to smell the roses

The wild roses are in full bloom and they are my first stop on each trip to the backyard.  As soon as I step out the door, I am greeted by their delicate and inviting fragrance.  However, I approach them hesitantly, scanning each blossom from a distance before stealthily drawing closer.  Although I have been caught by the thorns a few times in the past, my caution stems from a different source.

Many of the flowers harbor hungry predators waiting to pounce on their next meal.

A female crab spider (Misumena vatia) waits ready to grab its next meal with its raptorial forelimbs.

Of course, I am in no danger of ending up on the menu.  The predators are crab spiders; for them, even bumble bees are usually too large to handle.  The reason that I must move carefully is to avoid startling the spiders.  If I move too quickly or let my shadow fall over them, they may go into hiding underneath their flowers.

Instead of building webs, these spiders ambush their prey.  They have long forelimbs that they hold outstretched (resembling a crab's claws) until some unwary victim comes within reach.  Flowers are ideal hunting sites, since not only do they attract many insects, but also the insects are preoccupied with gathering food and may not notice the spider until it is too late.

As long as they are not disturbed, female crab spiders are unlikely to move much farther than to a neighboring flower.  This makes it possible to locate the same spider day after day.  But why take the trouble to look for something that sits nearly motionless for hours at a time?  By checking on a crab spider briefly each day, you can follow its progress as it tries out new hunting sites and strategies, changes color to match its current flower, consumes ever larger and more impressive prey, constructs a nest and guards its eggs.  If you are lucky (or set up a video camera), you may even chance upon the rare moment in which the spider moves with astonishing speed to grapple with its prey.

Therefore, even though these spiders will not harm you, you should be careful when you stop to smell the roses.

A male Misumena vatia eats a very small fly.