Zygiella x-notata

(Clerck, 1757)

missing sector orb weaver, silver-sided sector spider, Winter Spider, Opensector Orbweaver

Zygiella x-notata is an orb-weaving spider distinguished by its characteristic web with a missing sector in the upper half, connected by a signal thread to a peripheral retreat. females measure 5–11 mm, males up to 7 mm. The exhibits strong , commonly found on human structures such as window frames, walls, and fences. It has an with in summer and sac production in autumn. Native to Europe, it has been introduced to North America, New Zealand, and other regions worldwide.

Zygiella x-notata by (c) Alexis Lours, some rights reserved (CC BY), uploaded by Alexis Lours. Used under a CC-BY license.

Pronunciation

How to pronounce Zygiella x-notata: /zɪˈd͡ʒiː.ɛl.la ɛks nɒˈteɪ.tə/

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

The missing sector orb web is diagnostic: a gap in the upper half of the orb containing only a signal thread connecting the hub to a tubular retreat at the periphery. females recognized by leaf-like abdominal mark, silvery sheen, and grey-banded legs. Distinguished from Zygiella atrica (native to northwestern North America, complete web) and Z. nearctica ( distribution, complete web) by web structure and geographic range. Parazygiella (formerly Zygiella) typically build complete orb webs.

Images

Appearance

females: body length 5–11 mm, width ~1.5 mm. Prosoma yellow-brown. Opisthosoma displays a characteristic leaf-like mark and silvery sheen from guanine crystals beneath the skin. Legs grey-banded with dark grey wavy patterns dorsally. Adult males: smaller (up to 7 mm), dark exterior, dark brown legs and , smaller and less marked with shiny cream coloration. Both sexes possess on dorsal tibiae of legs and , with single on leg .

Habitat

Strongly ; primarily associated with human constructions including window frames, door frames, walls, fences, outdoor lights, boats, docks, and bridges. Also found on urban vegetation such as bushes and shrubs, and on cliffs. Prefers sites providing stable anchor points for web construction. Aggregates in high-quality web-building locations with densities up to 25 individuals per square meter.

Distribution

Native to western Palearctic region, abundant across Britain, Western and Central Europe. Introduced and established in North America (Pacific coast from California to Washington, Atlantic coast from New England to Virginia), New Zealand, and sporadically in South Africa, Mexico, Colombia, Ecuador, Panama, and Honduras. Also recorded from Azores (Corvo, Faial, Flores, Graciosa, Pico).

Seasonality

with present July–October in moderate climates, sometimes extending into December. In warmer regions, active year-round. Spiderlings emerge late spring, reach adulthood by August. occurs summer through early autumn.

Diet

Flying insects, primarily Diptera (flies, including Drosophila), captured in orb web. Prey type varies with geographic location and . Juveniles and females capture prey using signal thread vibration detection; adult males do not build webs and do not capture prey after sexual maturity.

Life Cycle

. Females lay in autumn (September–October), producing elliptical egg sacs white to yellow-brown in color with layered silk meshing. Spiderlings emerge late spring, disperse, and undergo several before reaching adulthood by August. female lifespan approximately 5–7 months. Males die after . Females may produce additional egg sacs in spring using stored sperm.

Behavior

Solitary but aggregates spatially near conspecifics. Builds modified orb web with missing sector and signal thread; web diameter 6–14 cm, signal thread 4–50 cm long. Juveniles rebuild webs daily; females renew webs as needed, typically at night. Sits in retreat with foreleg(s) on signal thread to detect vibrations. Upon prey contact, descends signal thread to hub, bites and wraps prey, transports to retreat for consumption. Exhibits web-jerking to locate motionless prey. Males use vibrational courtship signals (pulling, plucking, burping) on female webs. Shows -dependent web size adjustment and aggressive territorial behavior in . avoidance includes jumping from webs and web cleaning to reduce visibility to .

Ecological Role

of flying insects; contributes to local . Serves as prey for (particularly Vespula germanica). Web create localized hotspots. provide of insects near human habitation.

Human Relevance

Beneficial as agent of flying insects in urban environments. Non-dangerous to humans; venom not considered medically significant. Frequently encountered in domestic settings, often tolerated due to pest control value and non-threatening nature.

Similar Taxa

Zygiella atricaBuilds complete orb web without missing sector; native to northwestern Washington and southern British Columbia, not introduced throughout North America like Z. x-notata
Zygiella nearctica distribution (coast-to-coast Canada, Alaska, New England, Rocky Mountains, Appalachians); builds complete orb web
Parazygiella carpenteriFormerly placed in Zygiella; builds complete orb web; disjunct distribution in Sierra Nevada, California coast, southeastern Washington
Parazygiella disparFormerly placed in Zygiella; builds complete orb web; distribution southern British Columbia to Monterey, California

More Details

Signal thread structure

The signal thread is composed of 8–16 filaments in new threads (4–14 in repaired threads), formed by adding a dragline lifeline each time the spider runs between hub and retreat. Contains both major and minor ampullate silk; major ampullate silk's supercontraction enables tension control, while minor ampullate silk provides stability. Normalized load-bearing capacity remains consistent despite structural variation.

Web-building plasticity

Web construction responds to prey availability: spiders build earlier but produce smaller webs with narrower mesh when prey is present, optimizing for quick capture. Web structure becomes more regular with age and experience in younger spiders, while older spiders show greater variation and reduced silk investment.

Male choosiness and mate guarding

Males exhibit size-assortative mating preferences in competitive environments, with larger males guarding larger, more fecund females. Mate guarding occurs before female final to secure first copulation; larger males more successful at guarding and evicting rivals.

Predation vulnerability

Males experience higher rates due to lack of web , darker coloration increasing visibility on human structures, and exposed position during mate guarding. Females reduce predation risk through web cleaning, retreat use, and maintenance .