Bug o’the week – Splendid Dwarf Spider

Salutations, BugFans,


The BugLady saw these Splendid dwarf spiders (Hypselistes florens) when she did her dandelion survey (of recent BOTW fame) (unlike the large orb weavers of fall, these dwarf spiders overwinter in their almost-mature, second-last stage, ready to go in spring).  Later, she saw females making/tending to egg cases on blades of grass; she’s seen the white web patches for years and wondered who was responsible for them.


Splendid dwarf spiders belong to the spider family Linyphiidae, a large family (4,300-plus described species, and possibly that many undiscovered) of small spiders.  Linyphiids are second in species numbers only to Jumping spiders and are a dominant group of spiders in the cooler regions of the Northern Hemisphere (where they’re sometimes seen walking on snow).  Around the globe, they are known as sheetweb, dwarf, hammock and money spiders (in some countries, according to folklore, a dwarf spider walking on you has come to spin you a new set of clothes).  They belong to the subfamily Erigoninae, the dwarf spiders, whose members average about 2 mm in length – so small that it can be easier to identify them by their webs.

Bugguide.net tells us that “Sheetweb weavers are found in all kinds of habitats: anywhere there are small insects and at least a little vegetation to build their webs on.”  In fact, according to the University of Michigan’s BioKids site, “Some species in this family make their webs in the footprints of large animals, including people.”  Linyphiids are enthusiastic “ballooners,” both as spiderlings and adults, able to travel great distances on gossamer strands of silk.

Why “sheetweb?  Their three-dimensional webs are spun on or near the ground or in leaf litter http://bugguide.net/node/view/227371/bgimage.  In a typical web, a sheet (or two) of horizontal silk lies below a loose array of “knockdown” strands that are designed to intercept insects and cause them to fall onto the sheet.  The spider hangs (often upside-down) beneath the web, popping up when it detects the vibrations of its struggling prey.  It bites through the web, injects venom into its prey, and pulls it back down through the web.  Dwarf spiders eat invertebrates including springtails, ants, flies, planthoppers, and tiny beetles (in their own, small way, they do their bit for agriculture by feasting on some crop pests); they’re eaten by ground beetles, small amphibians, ants, centipedes, and other spiders.


Spiders have appendages on their face called palps; the palps of mature males are very conspicuous and are often compared to boxing gloves.  They have two body parts – an abdomen and a combined head and thorax called a cephalothorax.  The carapace (dorsal side of the cephalothorax) of males of many species of dwarf spiders is decorated with grooves or pits or projections or modified hairs.  These are assumed to play a part in courtship, and females of some species are known to grip them with their chelicerae (jaws) while mating.  Like tree crickets and some other arthropods, males of some species of dwarf spiders provide a bonus for their mates; a liquid that is secreted by special (prosomic) glands on his head is consumed by the female.


Sheetweb spiders can vocalize.  Like a katydid that strikes a rough spot on one wing against a rough spot on the other to make sound, a sheetweb spider rubs together gritty areas on its fangs to do the same.  They are only social during the mating season.

Splendid dwarf spider!  What a grand name for a spider that weighs in at less than 3/8” and can easily sit on the eraser of a #2 pencil (if anyone remembers what those are).  Splendid dwarf spiders are found from coast to coast, mostly across the northern half of the US and southern Canada.  They managed to cross the Atlantic – one male and two females were recorded in England in 1908 – but they did not establish a population there.

A few of the eight eyes of some males in the Erigoninae, including the Splendid Dwarf spider, are on mounds near the top of the head: http://bugguide.net/node/view/381724/bgimage.

The books say that this species makes its egg case close to the ground, but the BugLady finds them on grass stems that are two or three feet higher.  These common (but well-hidden) little spiders live for about a year.

Kate Redmond, The BugLady

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