Bolas spiders
| Bolas spider | |
|---|---|
 |
|
| Cladomelea debeeri | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Arachnida |
| Order: | Araneae |
| Suborder: | Araneomorphae |
| Family: | Araneidae |
| Tribe: | Mastophoreae |
| Genera | |
| Diversity | |
| 66 species | |
A bolas spider is any of several species of orb-weaver spider that, instead of spinning the typical web, hunt by using a sticky 'capture blob' of silk on the end of a line, known as a 'bolas'. By swinging the bolas at flying male moths or moth flies nearby, the spider may snag its prey rather like a fisherman snagging a fish on a hook. Because of this, they are also called angling or fishing spiders (although the remotely related genus Dolomedes is also called a fishing spider). The prey is lured to the spider by the production of up to three pheromone-analogues.
Bolas spiders are small nocturnal animals with oddly 'lumpy' abdomens. Females may grow up to 15 mm or 1/2", while the males, which are smaller, measure in at about 2 mm or 1/16". Several Mastophora species (e.g. M. cornigera) look like bird droppings, which enables them to rest unnoticed at day in fairly exposed places. M. bisaccata resembles the shell of a snail that is abundant in the spider's habitat. While the bird dropping mimics rest on the upper surface of leaves, M. bisaccata rests on the undersides. If removed from the surface, Mastophora females produce a pungent odor, which is highly unusual for spiders (other than bolas spiders, only one species of Cyrtarachne is known to do this). They do not attempt to flee when handled. Some species of Cladomelea also rest exposed on leaves during the day. However, the Australian Ordgarius magnificus, which displays eye spots on its back that make it resemble the moth they hunt, ties leaves together with silk to form a retreat. The females of some bolas spiders look remarkably like a bird dropping, thanks to their large, globular abdomen and brownish cephalothorax. This is a form of defensive mimicry as the animals that prey on spiders pay little attention to bird droppings.
Bolas spiders are species of three related genera:
Traditional orb webs are not effective for capturing moths, because only their scales will stick, allowing the moth to escape. The ladder webs of Scoloderus species appear to be adaptations in web design to increase moth capture. These webs extend vertically about seven times their width. When a moth slides down the web, it leaves a trail of scales until its body sticks to the web. However, these spiders do not seem to be closely related to bolas spiders. The nearest relatives seems to be the Cyrtarachneae (e.g. Pasilobus) of the Paleotropics. They also specialize on moths, and use threads that are beaded with sticky droplets. Celaenia and Taczanowskia species in South America seem to use chemical attractants to catch moths, too, and may also be closely related to bolas spiders.
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Wikipedia