Missing Sector Orbweaver

Sitting on the wall outside the front door was a small female spider, just begging to be photographed, Zygiella x-notata. Though I think it might have seen better days, having only 7 seven legs. The English name is Missing Sector Orbweaver Spider. It’s not a large spider, the body length of
males ranges from 3.5 – 5 mm; and the females are larger at 6 – 7 mm. One of the most distinctive identifying features is not the spider itself, but the web that it weaves. The adult builds an orb web which has two sectors without connecting threads, usually in one of the two upper corners. This pattern is common among other species of the genus. The signalling thread in the middle of these sectors leads to the spider’s retreat, where it waits at the edge of the web hidden amongst the foliage or other secure space (1-3).

The signal thread is built last during web construction and connects the central hub with the retreat, where the spider sits with one or two front legs monitoring the vibration of the signal thread (2). When the spider feels a vibration indicating that prey has landed on the web it will run to the hub along the signal thread. It is thought that the missing sector allows the spider to reach the centre of the web quicker along the signalling thread (2). However, if the spider builds in such a way that the signal line from the retreat is at a greater angle (about 40° or more) to the flat surface of the web – tit spins a full orb web (2). If the food supply is scarce the spider builds a larger web (2). These points indicate that web building can be altered by environmental factors.
Zygiella x-notata is widespread throughout the UK. It is usually found around buildings and structures, and its apparent distribution in the UK reflects this with the highest densities of records in the heavily populated urban areas. The most common places they can be found include window frames both inside and outside the house, under window sills and guttering and often on car wing mirrors (1,-3). Also found on garden shrubs and gate posts but usually in close proximity to human habitation (2).

Adult Season Data (based on 1663 records with adult season information) (4)

Adults can be seen all year round, but are most commonly encountered from July to about October, the males peaking in number in September and the females slightly later (4). However adult females can be found active into December and beyond. Mating occurs in September. After mating the males soon die. Egg-sacs are produced in September-October, (some even in the winter months), with the spiderlings emerging in early spring. The female produce two or three egg sacs and stays with them through most of the winter. Most females mature and reproduce in the year in which they hatch but some wait for the following year, when they are about 18 months old (2). They spend the winter in holes in external walls, which makes sense taking into account where I found this lady (2).

  1. Factsheet 6: Missing-sector Orbweaver (Zygiella x-notata). (2016). British Arachnological Society. Retrieved 2017.02.27.
  2. Zygiella x-notata. British Arachnological Society. http://britishspiders.org.uk/wiki2015/index.php?title=Zygiella_spp. Accessed 2017.02.27.
  3. Zygiella x-notata. Nature Spot. http://www.naturespot.org.uk/species/zygiella-x-notata. Accessed 2017.02.27.
  4. Summary for Zygiella x-notata. Spider and Harvestman Recording Scheme websiteSpider and Harvestman Recording Scheme. http://srs.britishspiders.org.uk/portal.php/p/Summary/s/Zygiella+x-notata. Accessed 2017.02.27.

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