May 18, 2017

Spider Bitten

Black Widow Spider ITALICIZE: (Lactrodectus mactans) Photo courtesy of CDC/Paula Smith; and J. Gathany|Hobo spider ITALICIZE: (Tegenaria agrestis) Photo courtesy of W. Cranshaw, CSU,||| Black Widow Spider ITALICIZE: (Lactrodectus mactans) Photo courtesy of CDC/Paula Smith; and J. Gathany|Hobo spider ITALICIZE: (Tegenaria agrestis) Photo courtesy of W. Cranshaw, CSU,||| ||||

by Dan Potts

Most people dislike spiders. Maybe they just look too spooky with their multiple eyes, hairy legs and big jaws. Fact is, almost all spiders are valuable to us because they kill and eat many of the pests that plague us.

There are more than 100 different species of spiders here in Utah, but fortunately, there are only two common spiders that pose a real threat to us here in Salt Lake City – the famous black widow and the lesser known hobo spider. Knowing more about these creepy critters is good, as merely fearing them does little to protect us.

Female black widow spiders with their recognizable round, shiny black body and red hourglass on the belly, are blind and only live in their very strong, somewhat irregular webs found mostly in dark, secluded places. They are non-aggressive and only bite in self-defense. Therefore, few people are bitten by them.

Hobos, on the other hand, build weak, funnel-shaped webs, have excellent vision, are aggressive, stand taller than other ground spiders, and can run very fast. While widows rarely find their way into our homes, hobos do. Male hobos leave their webs to roam far and wide in search of females in late summer and fall, and can enter our homes through the smallest cracks. Both species are primarily active at night, and roaming hobos are often fall into our sinks or bathtubs, where they are discovered in the morning.

Considered one of the most venomous spiders in the world, black widow bites can be very serious, especially to young children, the elderly or infirm. Hobo bites, on the other hand, are not usually serious. In their wandering, male hobos sometimes crawl into our beds at night where they can bite out of defense when we toss and turn in our sleep.

Because most hobo bites are not felt as we sleep, they go undetected, but can be identified as a red area with two pin holes about one quarter inch apart. While bites are usually not life threatening, they can result in swelling, nausea, infections from scratching, etc. My wife and I have woken up to find we have been bitten numerous times, and we have also been bitten by hobos hiding in our clothing. We hate them!

Measures to help prevent hobo bites include: plugging up access holes into the house, searching for and eliminating funnel-web spiders anywhere around the house, not leaving clothing and other “hiding places” on the floor, shaking out or examining shoes and clothing left overnight on the floor, and not allowing bedding to touch walls and/or floor in the summer and fall.

I certainly oppose the use of poisons around the house. However, hobos, as well as cockroaches and even pesky mice can be caught on “sticky traps” available at your local home and garden store. However, be very careful to read the instructions, as they can be dangerous around children and pets. Merely touching these highly “sticky” sheets of cardboard can result in a trip to the emergency room or veterinarian – far worse than a hobo bite!

To find more information on the hobo and black widow spiders and other common arachnids in Utah, visit