Segestria is a genus of spiders within the family Segestriidae, commonly known as tube-web spiders. These spiders are notable for their unique web construction and distinctive physical characteristics. The genus comprises numerous species found across various parts of the world, though they are particularly common in the Palearctic region.
Taxonomy
Segestria belongs to the following taxonomic classification:
- Kingdom: Animalia
- Phylum: Arthropoda
- Class: Arachnida
- Order: Araneae (Spiders)
- Family: Segestriidae
- Genus: Segestria
The family Segestriidae is part of the suborder Araneomorphae, often referred to as "true spiders" or "modern spiders," distinguished from mygalomorphs (tarantulas and their relatives).
Description
Segestria spiders typically exhibit a slender, cylindrical body shape. They range in size, with body lengths varying from a few millimeters to over 20 millimeters for larger species like Segestria florentina. Their coloration can vary widely among species, often ranging from dark brown or black to lighter shades with iridescent green chelicerae (mouthparts) in some prominent species.
A distinguishing feature of Segestria spiders is their eye arrangement. Unlike most spiders that have eight eyes, Segestria species possess six eyes, which are typically arranged in a semi-circle or an arc at the front of the prosoma (cephalothorax). Their legs are robust, and they are particularly known for their very long third pair of legs, which are often held forward and used to sense and manipulate prey at the entrance of their web. Their chelicerae are large and powerful.
Habitat and Web Construction
Segestria spiders are found in a variety of habitats, including urban environments, forests, and rocky areas. They are synanthropic in many regions, often found living in close association with humans, inhabiting cracks and crevices in walls, under stones, or beneath loose bark.
Their common name, "tube-web spiders," directly refers to their characteristic web structure. They construct a silk tube or funnel retreat within a crevice. From the entrance of this tube, several trip lines or signal threads radiate outwards. When an insect or other small arthropod brushes against these lines, the spider, typically waiting at the mouth of its tube with its long third pair of legs extended, senses the vibration.
Behavior and Diet
Segestria spiders are nocturnal predators. They are ambush hunters, waiting patiently for prey to trigger their signal lines. Once prey is detected, the spider darts out from its tube, quickly seizes the victim, and drags it back into the safety of its retreat to consume it. Their diet primarily consists of various insects and other small invertebrates.
These spiders are generally quite fast and agile. They are not typically aggressive but will bite defensively if provoked or threatened.
Medical Significance
The bite of some Segestria species, particularly the larger ones like Segestria florentina (the European tube-web spider), is known to be medically significant, although generally not considered dangerous to healthy humans. The venom can cause localized pain, swelling, and redness around the bite site, which may last for several hours or even a few days. In some cases, localized numbness, tingling, or itching may occur. Systemic effects are rare but can include mild nausea or dizziness in sensitive individuals. The pain has been compared to a bee sting. First aid for a Segestria bite typically involves cleaning the area, applying a cold compress, and pain relief if necessary.
Selected Species
The genus Segestria contains numerous species, including:
- Segestria florentina: The European tube-web spider, one of the largest and most well-known species, often found in urban areas across Europe.
- Segestria senoculata: The barreled tube-web spider, widely distributed across Europe, Asia, and North America, identifiable by its patterned abdomen.
- Segestria bavarica: Another European species, often found in similar habitats to S. florentina.