(Araneus trifolium)
The Shamrock Orbweaver Spider is from the family Araneidae. This spider is a very common and well-known orb-weaver spider that can be found on Vancouver Island. Individual spiders can range from light yellow to orange-brown or dark grey, but all cross spiders have mottled markings across the back with five or more large white dots forming a cross. The markings are usually quite visible. Adult females can grow to 20 millimetres in length, and males being smaller, are only up to 13 millimetres long.
This spider lives in most parts of North America, including all of Vancouver Island. Most people are unaware that most orb-weaver spiders were introduced to Canada from Europe.
The Shamrock Orbweaver is common in a wide range of habitats, including gardens, meadows, woodland clearings, and forest settings. It is frequently encountered next to buildings with exterior lighting and can be found in lighted stairwells of structures in rural areas.
These spiders catch flying insects, such as flies and mosquitoes, in their elaborate webs. The cross spider spins a large, complex orb web that is up to 1 meter in diameter to capture insect prey. These webs are built by large females. At the tip of their abdomens are 3 pairs of spinnerets, which secrete silk used to create the web. They usually face head down on their webs, waiting for prey to fly by and get entangled in the sticky webbing. Victims are quickly captured by the female and wrapped in silk before being eaten.
Orbweavers spiders are said to eat their webs each night along with many of the small insects stuck to the webbing. They have been observed eating their webs within the space of a few minutes. New webs are spun the following morning.
Adult spiders can be seen from late summer through autumn. In late September, females take leave of their webs and seek out protected locations in which to deposit between 300 – 900 eggs. These eggs are enclosed in a cocoon of yellow, silken threads. They are fascinating to watch as they hatch.