WSU Extension

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Spiders
 
Spiders 



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Caption: Orb weaver spider (Araneidae)
Photo by: D.G. James
  
Spiders : Spiders
(revision date: 10/23/2018)


Biology
Spiders generally evoke negative emotions in people but you should truly be grateful for their presence in your garden! The pest control service they provide is enormous and greatly under-appreciated. There are more than 800 species of spiders in Washington State and the average pesticide-free home garden is likely to be home to perhaps 20-25 species. Spiders occupy a range of habitat niches with correspondingly different behaviors and prey preferences. There are three main groups of spiders: those that spin and sit in webs to catch their prey, those that are very active, foraging for prey, often running it down, and those that sit still, ‘ambushing’ prey when it comes too close. Garden web builders are perhaps least threatening to people because they are fixed in location and not likely to surprise anybody (except the unfortunate winged insects that get caught in the web). Most often seen in late summer and autumn, orb-weaving or garden spiders spin their prominent and sometimes large webs in bushes and on buildings, fences etc, catching and feeding on any winged insect that gets trapped. Hunting spiders patrol backyards constantly searching for prey. Some species specialize on ground-living prey, others roam over plants and trees while others prefer to hunt on structures like fences and buildings. Jumping spiders (salticids) are small to medium–sized spiders (1/4 to ½ inch) with good eyesight that jump and pounce on their prey and are commonly seen in Pacific Northwest gardens. All hunting spiders find and devour a great number of insects every day. Ambush spiders are masters of disguise, quietly waiting for prey to come to them. Crab spiders (1/4 to ½ inch) are ambushers that often wait in blooming flowers for insects seeking nectar or pollen. Some sit on leaves waiting for an insect to land. Invariably, crab spiders are identically colored to their background and some can even change color according to background. Spend a little time looking for spiders in your garden and watch what they do. Your negative feelings towards spiders may just become positive!

Prey or Pest Targeted
  • Aphids, mites, caterpillars, flies, wasps, beetles, wasps, bees, grasshoppers, leafhoppers, whiteflies, thrips, mealybugs, moths, butterflies
     
Attracting and Keeping Natural Enemies & Pollinators in Your Yard
  • Avoid regular use of synthetic, broad-spectrum pesticides. Infrequent use of certain narrow-spectrum pesticides is more compatible with some beneficials but generally the less chemical inputs there are, the greater and more diverse the beneficial insect community will be. Extensive lawns are also not conducive to attracting and retaining a diversity of beneficial insects, mites and spiders. Minimize lawn areas and maximize shrub and bush plantings. Many beneficials reside naturally in riparian and other ‘natural’ areas near to many back yards. Natural dispersion from these refuges ensures that some beneficials will visit back yards but they will not stay unless food, host and shelter resources are available. Native plants have closer affinities with native insects and therefore provide most of these resources. A garden with a good diversity of local native flora in and around back yards, will improve the abundance and diversity of local, beneficial arthropods. Native flora also provides natural overwintering sites for many beneficial insects and it is useful to leave at least a small area of native vegetation undisturbed during fall and winter.
  • Some kinds of beneficial insects (e.g. lady beetles, lacewings, predatory mites) are available for purchase from commercial suppliers. However, benefits from introducing these beneficials are usually limited and short-lived. Upon release, commercially obtained lady beetles and lacewings often disperse and may rapidly leave your backyard despite the presence of prey and suitable nectar resources. Generally, it is more effective and sustainable to create a garden habitat that will be colonized by beneficials naturally.
     

Images

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Caption: Orb weaver spider (Araneidae)
Photo by: D.G. James
Caption: Jumping spider (Salticidae)
Photo by: D.G. James
Caption: Crab spider (Thomisiidae) welcoming prey
Photo by: D.G. James