Dwarf spider

Spiders in the subfamily Erigoninae are called dwarf spiders in the United States. In the British Isles, these spiders are called money spiders and are thought to bring good luck and wealth.

Kingdom: Animalia

Phylum: Arthropoda

Class: Arachnida

Order: Araneae

Family: Linyphiidae

Genus: Various (see below)

Species: Various (see below)

Dwarf spiders are found throughout the world among low-growing vegetation of shady woods, grasslands, gardens, and forests under leaves or other cover. Thousands of dwarf spider species belong to the subfamily Erigoninae and are organized in many genera, including Erigone, Atypena, and Hylyphantes.

As its name suggests, dwarf spiders are small, growing to 1/6 of an inch (less than 1/2 a centimeter) long. Like other spiders, the dwarf spider is divided into two main parts—cephalothorax and abdomen. The cephalothorax is the head and thorax, or mid-body section. The cephalothorax of the dwarf spider is typically long and narrow. The rounded abdomen is the lower-body section. This portion contains most of the internal organs of the dwarf spider. The cephalothorax is also known as the prosoma and the abdomen is also known as the opisthosoma. Between the cephalothorax and the abdomen is a narrow connecting tube called the pedicel.

Some species of dwarf spiders can glow in the dark because of a trait called bioluminescence. This helps them attract prey at night. Most dwarf spiders are black, brown, or white. The Floronia bucculenta can change colors when disturbed or threatened, which is rare among most families of spiders.

Like many spiders, the dwarf spider has eight legs extending from the lower portion of the cephalothorax and a pair of palps extending from the head of its cephalothorax. The palps are used for tearing and grasping. These appendages are especially helpful in web construction and removing prey from silken strands.

Despite its small size, dwarf spiders construct large, thick webs of silken threads. The main part of the web is like a sheet above which are many individual strands of sticky silk. As insects move through the low-level vegetation of the woods, they become stuck on these strands. Many insects fall to the sheet below upon becoming entangled in the sticky silken strands. The spider waits on the sheet-web and quickly collects its victims as they fall. The insects are killed by a final bite.

Dwarf spiders begin the mating process during the warm weather of the spring. Males attract females using dances and vibrations. Like other spiders, they reproduce by direct fertilization. With this, the male's sperm is released directly into the body of the female. Mammals also reproduce by direct fertilization.

After mating, the female lays her eggs. She covers her eggs with silken threads within her web. After a short developmental period within the eggs, the young dwarf spiders hatch. They stay on their mother's web until they are old enough to survive on their own.

Dwarf spiders' lifespans depend on the species, but they generally live up to three years.

Dwarf spider species include:

Horrid ground-weaver spider Nothophantes horridus

Horse-head spider Stemonyphantes lineatus

Splendid dwarf spider Hypselistes florens

Bibliography

Ballarin, Francesco, and Takeshi Yamasaki. “Nihonella Gen. Nov., a New Troglophilic Genus of Dwarf Spiders from Japan with a Discussion on Its Phylogenetic Position within the Subfamily Erigoninae (Araneae, Linyphiidae).” European Journal of Taxonomy, vol. 733, 26 Jan. 2021, doi.org/10.5852/ejt.2021.733.1215.

"Dwarf Spider ID Gallery." Field Museum, www.fieldmuseum.org/science/special-projects/dwarf-spider-id-gallery. Accessed 5 Apr. 2024.