Tropical garden animals - spiders


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Spiders Class: Arachnids Family Araneidae
Species: Argiope (mangal?) Family: Araneidae English: St. Andrew's Cross Spider Indonesian: cannot find an Indonesian name, but wouldn't be surprised if it is the translated English: Laba-laba Santa Andreas Size (legs not included): female: 15 mm male: 5 mm So far I discovered one species of orb web building spider in my garden: the St. Andrew's Cross Spider. It got its name because of the position of its legs when it sits in the centre of the web. Usually I can find five or more inhabited webs of this species, but during certain months there is not a single one. Webs are located up to three meters above the ground. The St. Andrew's Cross Spider is relatively easy to photograph as it is not shy and does not move when the camera lens comes nearby. Its web has often two or four characteristic zigzag lines near the centre called "web decorations" or "stabilimenta". There are three explanations for this phenomenon, that might be all true: - They stabilise the web (hence the name "stabilimenta") - They make the web better visible for passing animals like birds. This reduces the risk of damage like paint does on windows of houses under construction. - They give the impression of flowers to insects. Research has shown that the silk used for the zigzag lines reflect ultra-violet. Many flowers have different UV light reflecting and absorbing zones to guide insects to the pollen and nectar. After the female spider has mated with the far smaller male spider it will lay its eggs in a egg sac made of silk. This egg sac is usually long stretched and attached near the edge of the web. A St. Andrew's Cross Spider that I could observe easily, because it made its web next the door of my house, had finally four of these sacs in its web: two in the top and two down at one of the main threads. The eggs sacs were made with at least a week interval. The young hatch after about five days and leave the mother's web in small groups sitting on long very thin and light threads that are easily carried away by the wind. Sometimes these threads make a bridge between the mother's web and an other place. Argiope in web (top left) with egg sacs (down right)		Argope seen on its back. Note the silk zigzag stripes in the web. The spiders always hang with their head down in the web. At the moment the web is hit by an unlucky insect the spider quickly ties it with a few threads and wraps it into a part of the web (see photo below). After this the spider sucks the fluids out of the victim and will finally drop it.
		Argiope - big catch!
The photo on the right shows the front of a St. Andrew's Cross Spider hanging head-down in its web. I still have to learn the different parts of the spider body, but guess that at the top (the 'bottom' of the spider) is the part that releases the silk surrounded by the 'spinnerets'. Somewhere in centre of the abdomen should be the opening to the reproductive organ. Sitting (or hanging) in its web this spider holds its legs in pairs of two. The two other leg-like body parts at the bottom of the picture are the pedipalps, that function as an organ of touch. Behind the pedipalps are the fangs that inject the venom in the trapped prey. Web spiders do not have a good vision. With the hair on its legs the spider can feel vibrations. This warns the animal for approaching predators.	Argiope, close up of front

Species: Plexippus paykulli? Family: Salticidae (Jumping Spider Family) English: Larger Housefly Catcher? Indonesian: ? Size (legs not included): 8 mm. The tiny spider on the right I found on a wall in the (rather dark) bathroom. It does not make a web to catch its prey, but just jumps on it. Different from web spiders this type of spiders has a good vision needed to locate the prey. The macro photos I could make after catching it and placing it in a glass jar (somehow the spider's legs are less suitable for climbing glass). In the photos I can only discover six eyes. Four eyes are placed in the front row. The central two of these are very big. Two other eyes are placed more to the back of the cephalothorax (head combined with thorax). Based on the position of the eyes, the length of the legs and the way it moves I think it is safe to say this is a Jumping Spider. Before it jumps down or over open space it attaches first a thread to the place it starts. In case it misses its target the thread will prevent the spider to fall far down. After photographing I released the spider again in the bathroom. Though it had "seen the light" it just stayed there. Probably it preferred the place because there usually is enough food to find.		Plexippus paykulli - Larger Housefly Catche?
		Plexippus paykulli - Larger Housefly Catche

Species: ...? English: Wolf Spider? Jumping Spider? Indonesian: ? Unfortunately the photo I made of the spider shown at the right does not show the position of the eyes clear enough. Because of that it is hard to find out to which group this spider belongs. Is it an other Jumping Spider, or may be a Wolf Spider? Strange enough this spider has some spots on its abdomen that look like eyes. Could these be false eyes? The main characteristic used for identifying the group of Wolf Spiders is the row of four small eyes with two big eyes above it. Two smaller eyes are placed behind the two big eyes. Wolf spiders are said to hunt most of the time on the ground. I found this spider on a wall in the garden. So, not a wolf spider? Probably it is as well not a jumping spider, as its 'face' is not flat to give place for the two big eyes like can be seen in the picture of the jumping spider ("Larger Housefly Catcher"?) above. I hope to meet this white hairy fellow again and take a closer look.

Species: ...? English: Jumping Spider? Indonesian: ? This little fellow (4 mm?) on the right I found one day on my arm when I was sitting in the back yard. Unfortunately this picture was the only shot I could make of it, as it soon escaped. This kind of spider is fast and is moving continuously. It looked more yellowish to me when I first saw it. Its legs look transparent; are they really? I will have to wait for an other meeting with this fellow to find out more details. Like the Larger Housefly Catcher shown above it has two characteristic large eyes in front with smaller eyes next to it and some small eyes more to the back of the head (actually cephalothorax). Probably it is more hairy than the picture shows.

Species: Heteropoda venatoria Family: Sparassidae (Huntsman Spider Family) English: Domestic Huntsman Spider Indonesian: ? Size (legs not included): Female: 23-33 mm. Male: 20-30 mm. In many houses in the tropics you will find Huntsman Spiders. It was not a surprise to find some in my house. Though these animals are not aggressive they have often scared guests visiting the bathroom: they can grow big. They seem to move freely between the rooms with open windows and the garden. The spiders walk more or less sideways. It is said that "females can be recognised by a white band across their "faces" (clypeus). The males seem to have a pair of dark brown patches on the carapace". I still have to find out what this all means and who is male or female. I am not really sure what all is on these spider's diet. One thing I have noticed is that they go for cockroaches. That's good! The spiders lay their eggs in an egg sac carried under the body. I still like to find out what size the young spiders are when they appear from the eggs and how long they stay after that in the sac.		Domestic Huntsman Spider
On the right some photos of an left old 'skin' of a Huntsman Spider. In fact this is an external skeleton (exoskeleton), which gives support and protection to the body contents. The exoskeleton does not grow with the spider. The spider leaves it after it grows to big. It has developed a new skeleton inside before that can happen. It is interesting to see that all external parts, including hair, fangs and the outer layer of the eyes are shed. The eyes are clearly placed in two rows of four. The eyes at the outside of the rows are slightly bigger.	A shed Huntsman Spider exoskeleton showing the two rows of four eyes and the fangs
	Opening and part of the abdomen in a shed Huntsman Spider exoskeleton


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