Tuesday, 30 November 2010

Thomasis spectabilis (white crab spider)

This is the same photograph that I showed on the previous post.  I didn't know what kind of spider it was,  so what could I do but put it on Facebook and ask my friends.... (what else would you do?)
 Dion Ashenden has found the answer...

 Thomisus spectabilis (White Crab Spider).
A short, squat spider, from 3-11mm, common in Summer, Australia wide, active in the day time. Some can be very white (if living in white flowers). Some can be quite yellow. They sometimes have yellow-reddish ends to the translucent legs, and black markings at the rear of the trapezoidal abdomen. The first and second pairs of legs are noticeably longer and thicker than the last 2 pairs. Lateral eyes are on projections. Males are smaller. There may well be several species of Thomisus being found, grouped together under the name Thomisus spectabilis. Many juveniles that appear Thomisus-like have brown eye patches. They generally hunt on flowers or other parts of plants matching their colour though they can change colour to match the plant. An insect visiting the flower for pollen or nectar is seized and bitten, then sucked dry. Eggs are laid in a silk dish covered with a lid where they stay for up to two weeks. When the spiderlings hatch, they are left to fend for themselves.

Crab spiders are no active hunters. They make more use of the camouflage techniques than other spiders and catch their prey with their front legs. The color of the spider is adapted to the hunting terrain they use and is mostly extravagant. They remain unmoved until the prey arrives and catches it. With a poisonous bite (not dangerous to humans) they kill their prey and suck it dry. They can be found on flowers or leaves of plants. Often the crab spider remains for days, even weeks at the same spot. The front two legs, that are often larger and stronger than the other six, are held sideways, ready to catch the prey immediately. Because they sit on easily spotted places they are also easy to catch by the predators. When they spot a possible enemy they move quickly at the other site of the flower or leave. Their eyesight is excellent developed as can be seen on the pictures. They have normally two big front eyes.

Crab spiders are easy recognizable if you tease them. They widen their legs and move side ways like a crab. Their size is between 4 - 10 mm.

The females usually stand guard with their egg sacs. The egg sacs are fastened to the vegetation and are usually flat.
The reference is here.

I have also found another individual that looks quite different....

... and then I saw the other (first) one catch a fly!!!
This is really interesting from a number of points of view...  my flowering vegetables and herbs have attracted ladybirds and hoverflies that prey on aphids (much to my delight) but this addition to the food chain is quite amazing.   There are plenty of ladybirds on these parsley flowers, and all sorts of flying creatures... no doubt a great place for a spider to catch such insects.   
While I want most of the species that appear to be his/her prey,  this is the real situation in a healthy ecosystem and what else could I ask for?




2 comments:

Tiff Elizabeth said...

Ope. Just saw this!! Thank you!

Jane said...

Glad that you found it. These spiders are not dangerous.