On this Earth Day, say "Thanks!" to a spider

This cute little fellow is a member of the family Salticidae, the jumping spiders.  The common name is apt.  Although he looks almost cuddly these spiders are active, daytime hunters that can jump to catch their prey.  They have big eyes, unusually good eyesight, and can jump several times the length of their body.  Jumping spiders use a dragline - they tether a line of silk to the surface before they jump - and then use that to catch themselves if they fall or to climb back to their original spot.  Other than as a tether, jumping spiders do not use silk or webs to catch prey.  They will build silken shelters, however, where they sleep, overwinter, and protect their egg sacs.

This species of spider is not from here, it is native to South America.  We don’t know how it arrived, but it was first collected in the US in Louisiana in 1944 and it spread across the Gulf states and beyond; it was first collected in San Diego near Clairemont High School in 1997.  Since then it has become widely established in urban southern California.  A prominent local arachnologist was able to “collected 13 in his San Diego backyard in 12 minutes”.   We also don’t know if it is simply a non-native species or if it has crossed the line into being invasive - a species that causes harm, typically by reducing biodiversity.  There is some suspicion that M. simoni outcompetes a native spider in Florida, but we have no such information here in California. 

This DNA sequence for this individual had no match in the DNA barcode reference library!  This does not mean that it is “new to science” but it does mean that no one has yet sequenced & uploaded its DNA to this database.  The closest match was to the genus Geolycosa, however, so we will guess that it is in the wolf spider family (Lycosidae).  As the name suggests, wolf spiders are active hunters that do not build webs.  Unlike most spiders wolf spiders have excellent eyesight.  You can see the extra big eyes in the photo.  Wolf spider mothers are the only spiders known to carry their baby spiderlings on their back for several weeks until they can live on their own.  Sweet!

This species is in the family Theridiidae, the comb-footed or cobweb spiders.  The name comb-foot comes from the row of comb-like bristles on their hind legs; the name cobweb spider comes from the messy, irregular tangle of silken threads that is their web, so unlike the symmetrical orb webs (like the silver Argiope photo above) or shapely funnel webs of other spider families.  This  family contains the spiders that are most likely to be in your home, in fact this genus is referred to as cupboad spiders. Black widow spiders are also in the family Theridiidae, but Steatoda grossa is thought to prey on black widow spiders (Insects of Los Angeles Basin).  So again, today is a good day to thank a spider!

Wander the Wetlands is an open-house-style event at the Kendall-Frost Marsh every 2nd and 4th Saturday. You can chat with a docent, look at birds through a spotting scope, or just relax on the porch and enjoy the view of the wetlands & Mission Bay.  No pre-registration is necessary.

Every Friday we tackle the invasive weeds at the Scripps Coastal Reserve.  Devil's thorn (Emex spinosa) and crystalline ice plant (Mesembryanthemum crystallinum) are our current focus. No experience necessary!  Please email nrs@ucsd.edu if you would like to join the fun.

Wander the Wetlands is an open-house-style event at the Kendall-Frost Marsh every 2nd and 4th Saturday. You can chat with a docent, look at birds through a spotting scope, or just relax on the porch and enjoy the view of the wetlands & Mission Bay.  No pre-registration is necessary.

Come to Kendall-Frost Marsh on the 3rd Saturday of every month to help out with restoration activities.  Help plant native plants, weed invasive species, mend rabbit-deterring fencing, and lots of other tasks to give some TLC to the marsh and surrounding uplands. Please email nrs@ucsd.edu if you would like to participate.

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