Identification Tips for Brown Spiders of the Eastern US
Knowing What is and is Not A Brown Recluse or Wolf Spider
I'm often amazed at the number of times I've been outdoors with someone and when we see a brown spider immediately someone says, "Look, there's a wolf spider." I have to admit, I hate identifying "little brown jobs" or LBJs (a term we use commonly for brown sparrows when birding) because it's hard to find the fine distinctions between species, especially when the creatures are moving or you're just skeezed out by the hairy eight legged creature crawling across your floor. However, it is important to understand that not all brown spiders are wolf spiders.
There are many different types of brown spiders and this blog post will help you begin to differentiate between them. I'm going to write mostly about the spiders common to Eastern and Mid-western North America, because this is my home range, but there is some overlap with Western species.
A great starting place to learn spider ID and to become familiar with their body parts, names, and the eye placement of spiders is on the website "Spider Identification Guide." I am particularly fond of their great graphic on the 25 different eye patterns you can find on spiders (I wonder if they make this in poster form?). Begin with the basics of spider anatomy on their website if you need a refresher. They also have a great guide for finding spiders by region and color. Check out their page on "Brown Spiders" for a quick browse of the diversity out there.
Of course I don't have enough time to cover all the potential brown spiders that exist so I'll start with a few of the more common ones.
First, not all spiders build webs. Many of the brown spiders that we see are wandering and hunting spiders or those that live in grass and shrubs. It's the hunting spiders that most often frighten people because they tend to crawl around in homes and houses, especially at night, where we interact with them more than the ones that build webs and just hang-out. There are some exceptions, like the funnel weaving spiders that live on or near the ground and whose webs are not sticky. They use their webs to lure prey and for hiding places. Brown recluse spiders build shoddy looking asymmetrical webs but they also wander around at night to hunt. Not to fear though, because most often spiders (brown or otherwise) are completely harmless and they're actually eating harmful insects in your home.
The four main spiders to start with are:
1. Wolf spiders (specifically Carolina wolf spider)
2. Grass spiders (specifically the common American funnel-web spider)
3. Fishing spiders (like the six spotted fishing spider)
4. Brown recluse (Loxosceles reclusa)
5. Nursery web spiders (specifically Pisaurina mira, no common name other than nursery web spider).
There are many, many, many different types of wolf spiders, grass spiders, nursery web spiders etc..and there are many color variations. This makes generalizations difficult, but with the chart below I'm going to provide you with some photos and descriptions so that you can begin to narrow down your ID of those LBJs.
Let's start with some pictures to help you begin to compare these species visually:
Notice, in the picture above, of the wolf spider the distinct tan strip coming down the cephalothorax (fused head and middle section) and the dark stripe on the abdomen. If you look closely you can also see that it has 3 rows of eyes (8 total eyes).
Common grass spider (Aglenopsis naevia) (Photo: Flicker, Jeremy Hall)
In the picture of the grass spider notice the three stripes on its cephalothorax (head-thorax); the two distinct spinneretts on the abdomen; small narrow abdomen, and tapering legs.
With the six spotted fishing spider you can see the clear white stripes on the cephalothorax, the white mottling on the legs, two rows of eyes, and the large white streaks on the abdomen along with six dots (thus the name). Being by water also gives this guy away.
Notice the small size of the brown recluse, its thin narrow legs, and the characteristic violin shape, starting at the eyes (with the body of the violin) and the neck of the violin going down the center of the cephalothorax. The abdomen is pretty nondescript.
Nursery Web Spider
For the nursery web spider notice its legs are held in almost the figure eight and the cephalothorax is somewhat pear shaped with a dark brown stripe down the middle continuing down the abdomen. There is also a border of white or cream color on the abdomen. Their eyes are in two rows, the top row is U shaped and the bottom straight.
Here is a chart to compare some basic physical characteristics:
|Wolf Spider||Grass Spider||Fishing Spider||Brown Recluse||Nursery Web Spider|
|Most Common Species||Genus Hogna, Carolina Wolf Spider||Genus Agelenopsis, common American Funel-web spider||Dolomedes triton, six-spotted fishing spider||Loxosceles reclusa, brown recluse or violoin spider||Pisaurina mira, Nursery Web Spider|
|Size||.05 mm-40 mm||.05 mm-19 mm||.05 mm-26 mm||6 mm-20 mm||.05 mm-76 mm|
|Color||Ranges from buffy tan to blackish grey||brown to dark brown||Coffee Brown to dark brown||dark brown to greyish||6 color variations, but most common buffy brown/tan|
|Markings on Abdomen||Greyish-brown stripe down abdomen||Note: 2 clearly visible spinneretts on abdomen, Buffy brown, sometimes with triangle shapes down length||Pale whitish stripe down abdomen||Nondescript brownish grey abdomen||dark brown line down center of body, sometimes two creamy stripes down sides|
|Markings on Cephalothorax (head and thorax fused)||In genus hogna, distinct whitish to creamy white stripe running down middle||Pear shaped cephalothorax, with two heavy dark bands on either side, light stripe down middle||Pale whitish stripe down sides of cephalothorax||Distinct violin shape, with the violin body stating at the mouth and the neck heading towards the abdomen||Cephalothorax is pear shaped, often with two white stripes along sides.|
|Eyes||3 rows of eyes: 2 medium on top of head, 2 large facing forward, 4 smaller on third row.||8 eyes in 3 rows, bottom row of eyes spaced wider than top rows.||8-all the same size in two rows||6-one middle pair and two side pairs, all the same size||8-all the same size, in two rows of four|
|Hunting Habits||Nocturnal hunting, solitary, jumps on prey||Builds a funnel web in grass, runs quickly and grabs prey from web||Nocturnal or diurnal,Sits near water, feels vibrations, hooks prey with claws on front feet, injects venom; pond skater on and below water||Sits with all legs extended, nocturnal or diurnal, doesn't prefer to jump on prey, bulids asymetrical webs in dark places, hunts at night leaving web||Rest with legs flattened out to side, often in X shaped posture|
|Egg Sacs||Attach under rear abdomen||Placed on nursery web||Placed on nursery web||Placed on web.||Carry egg sacs in their mouth parts|
|Young||Females carry young on back||Young guarded in nursery web until hatching||Young guarded in nursery web until hatching||Young hatch on web.||Female builds nursery tent and guards until young hatch|
|Venom||Irritating but not life threatening||Not able to penetrate human skin, harmless||Irritating but not life threatening||Potentially deadly hemotoxic venom, may cause necrosis||Nonvenomous|
|Eats||Crickets, grasshoppers, pill bugs, etc.||Variety of field insects, crickets, flies, etc.||fish, tadpoles, aquatic insects||Crickets, roaches, pill bugs, etc.||Walks on water, tadpoles, water insects, worms, pill bugs|
Most people will never want to get close enough to a wolf spider to be able to tell it apart from a grass spider, but for those of you intrepid enough to want to try I encourage you to get out there and look around. There are many more spiders than wolf spiders, and 99% of them are harmless and beneficial helpers around our house and yards. Take time to appreciate the LBJ's of the spider world, they're actually good neighbors.
Check out these additional resources for more information:
- One of the best guidebooks on spiders: Common Spiders of North America by Richard Bradley
- For kids: Learn About Brown Recluse Spiders and Enjoy Colorful Pictures, by Becky Wolff with over 50 photos of Brown Recluse Spiders
- Also for kids: Spiders: Amazing Pictures & Fun Facts on Animals in Nature from bestselling children’s author Kay de Silva