Splendid Spiders

Intrigued by the fascinating 8-legged creatures of Halibut Point I sent away for a copy of Common Spiders of North America by Richard A. Bradley.

Hentzia palmarum, a jumping spider

The book takes a different approach to cataloging its subject than most insect identification guides which are organized by genetically-based anatomy. Much of Common Spiders is based on behavioral and habitat groupings as presented with my photos below. This can prove helpful in field observations.

Mecaphesa asperata, Northern Crab Spider

Unlike insects that have three main sections of the body, spiders’ bodies are condensed into two main sections. In the front its fused head and thorax are typically fused, comprising the eyes, fangs, stomach, legs, and brain. At the rear its abdomen holds the spinnerets used for making webs. 

Every spider has 48 knees, one for each of the 6 joints on its 8 legs.

ORB-SHAPED WEB GROUP

Leucauge venusta, Orchard Spider

These spiders produce webs in a pattern of sticky lines spiraling out from the center of a flat frame, supported by a series of spoke-like radial strands.

FUNNEL-SHAPED WEB GROUP

Agelenopsis sp., Grass Spider

Hiding within a tubular retreat, these spiders run out to capture prey trapped in or walking on the web.

SHEET WEAVERS GROUP

Florinda coccinea, Black-tailed Red Sheet Weaver

Sheetweb weavers await their prey hanging upside down directly under or beside the web rather than in an adjoining retreat.

UNDER DEBRIS GROUP

Dictynidae sp. - Mesh Web Weaver

'Under debris' spiders are usually discovered by turning over logs, boards or rocks, where they have formed this sheets of webbing.

SPACE-FILLING GROUP

Enoplognatha sp.

These spiders make three-dimensional tangles of lines to entrap insects passing through an area. 

JUMPING SPIDERS GROUP

Zygoballus sp.

When hunting or trying to escape a predator, jumping spiders are able to make very agile movements and jump multiple times their body length. This is possible due to an internal hydraulic system. Jumping spiders can alter the pressure of fluids in their legs resulting in a springing motion that propels the spiders forward.

CRABLIKE SPIDERS GROUP

Misumena vatia, Goldenrod Crab Spider

Many crablike spiders wait in ambush within a flower, arms outstretched to catch insect pollinators.

SURFACE HUNTERS GROUP

Pisaurina mira, American Nursery Web Spider

Rather than constructing static traps the surface hunters wander over landscape features, plants and streams in search of prey.

GROUND HUNTERS GROUP

Cesonia bilineata, Two-lined Stealthy Ground Spider

Similarly, ground hunters pursue prey with vision and speed superior to many other species.

Sergiolus capulatus, Variegated Ground Spider

Spiders may be colorful not only on the outside. They have pale blue blood because its oxygen is carried by hemocyanin containing copper, unlike the hemoglobin found in humans that gets its red color due to using iron.