By James A. Bethke.
When I was a teenager, I collected a whole bunch of very small jumping spiders into small, clear, plastic containers and watched them for hours using a hand lens. I was fascinated by their predatory behavior and how colorful they were. Their true beauty is hidden due to their small size and the fear of spiders in general. However, jumping spiders are a gardener’s best friend!
In order to feed the small jumping spiders, I had to catch tiny flies and somehow get them into the container with the spider. Then watch them hunt the little flies down and eat them. Yup, my wife married me anyway.
There are over 6000 described species of jumping spider in the spider family Salticidae. In my exploits and even in my job, I have seen a tremendous number of different kinds of jumping spiders including the large (3/4-1 inch) red backs. The larger ones are quite impressive with jet black heads, metallic gold or copper jaws and multicolored abdomens, which are mostly red. When disturbed, these bigger jumping spiders will raise their front legs and show their fangs in defense.
Most spiders can’t look at you, but jumping spiders have great vision and when they see movement, they will look right at it. I can’t tell you how many times I have watched jumping spiders turn and look at me like the one I stalked for hours on our rose plant (Fig. 1). The large pair of eyes in the front of Salticids are adapted to telescopic, three-dimensional vision, which helps estimate the range, size and type of prey. This allows jumping spiders to direct their leaping attack with great precision. The other six eyes (spiders have 8 total) give the spider a nearly 360-degree view of movement. The depth and distance vision is from multiple retinas at different depths in the back of the eye that can see red and green differentially. Very fascinating. Most of the time they are hunting small insect pests such as aphids, whiteflies, gnats and other soft bodied insects. I have seen jumping spiders miss their prey and hang for a moment on silken thread. They attach a little webbing to the jumping off point as a safety line, just in case.
One of the most fascinating things about jumping spiders is their complex courtship displays (see about peacock spiders: https://www.peacockspider.org/). Male spiders use their elaborate front legs to conduct a courtship dance in which the colored or iridescent parts of the body are displayed. There are lots of videos online of these behaviors.
I have provided some fascinating facts about jumping spiders, but the real value of these creatures is their generalist, predatory behavior in the home and garden. Obviously, they are in my yard, but I have also seen them in commercial greenhouses and nurseries searching for food on the plants. In greenhouses, they eat fungus gnats, whiteflies, shoreflies, etc. I have also seen them inside leaves that have been webbed together as a shelter, many times protecting an egg mass.
I hope the next time you see jumping spiders in your home or garden, you will take the time to take a look and observe their fascinating behaviors. They are nothing to be afraid of and you should consider them one of the good guys.
Images of jumping spiders in north America: http://salticidae.org/salticidImages/pages/usacanada/classification.html
More images of jumping spiders: https://bugguide.net/node/view/1962
James A. Bethke is Emeritus Advisor, UC Cooperative Extension.