Scopulae, or scopula pads, are dense tufts of hair at the end of a spiders's legs. They are found mostly on hunting spiders, especially Lycosidae and

Salticidae Jumping spiders are a group of spiders that constitute the family Salticidae. As of 2019, this family contained over 600 described genera and over 6,000 described species, making it the largest family of spiders at 13% of all species. Jumping spi ...

. Scopulae consist of microscopic hairs, known as

seta In biology, setae (singular seta ; from the Latin word for "bristle") are any of a number of different bristle- or hair-like structures on living organisms. Animal setae Protostomes Annelid setae are stiff bristles present on the body. ...

e, which are each covered in even smaller hairs called setules or "end feet", resulting in a large contact area. When the scopulae are splayed out and placed against a surface, remarkable

adhesion Adhesion is the tendency of dissimilar particles or surfaces to cling to one another ( cohesion refers to the tendency of similar or identical particles/surfaces to cling to one another). The forces that cause adhesion and cohesion can ...

is produced due to the accumulation of adhesion of each individual setule interacting with a substrate. The adhesion may be due to the excretion of liquid from adhesive pads, although setae can adhere in both dry and wet modes. This enables

spider Spiders (order Araneae) are air-breathing arthropods that have eight legs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude silk. They are the largest order of arachnids and rank seventh in total species ...

s with scopulae to climb even sheer, smooth surfaces such as glass. The adhesion is so great that the spider could grip using this force and support 170 times its own weight. Possible physical mechanisms may include capillary, electrostatic, viscous, or

Van der Waals force In molecular physics, the van der Waals force is a distance-dependent interaction between atoms or molecules. Unlike ionic or covalent bonds, these attractions do not result from a chemical electronic bond; they are comparatively weak and ...

. (Niederegger et al 2002; Betz and Kölsch, 2004) Scopulae have been used in taxonomy to identify families, especially Mygalomorphae. Scopulae are found in addition to, not instead of, the claws at the end of each appendage, called

tarsal claws This glossary describes the terms used in formal descriptions of spiders; where applicable these terms are used in describing other arachnids. Links within the glossary are shown . Terms A Abdomen or opisthosoma: One of the two main body parts ...

References

{{Spider nav Spider anatomy