• Home
  • Environmental Monitoring

Land Snails and Millipedes Transect

Large millipede - Blue Ridge ParkwayIn spring and summer of 2017 Park staff and citizen scientists inventoried land snails and millipedes along the Blue Ridge Parkway. Contact This email address is being protected from spambots. You need JavaScript enabled to view it. for more information.

Data Map

Both land snails and millipedes are extremely important for decomposing leaf litter. Land snails are an important source of the calcium breeding songbirds need for their eggs and some species produce slime when they are threatened that fluoresces under UV light. In addition to offering two in-person training sessions this spring, training information will also be posted on Hands in the Land and use the great resource of the website for coordinating the collecting effort and sharing the data.

Related Files

Triodopsis snail, side view (NPS photo)


Land snails are an easily overlooked and understudied part of the ecology in the southern and central Appalachians. Of the more than 1,000 species known to occur in North America, 25 have been identified on the Parkway, but another 125 are likely to be found here, some of which may be rare or even endemic.

Land snails, semi-slugs, and slugs contribute significantly to decomposition and nitrification of soils through their decaying bodies and feces. Their dead shells are a principal source of calcium. Land snails recycle forest nutrients and are prey for a number of vertebrate (amphibians, reptiles, birds, and mammals) and invertebrate (insects, carnivorous snails) species. Carnivorous snails feed on earthworms, insect larvae, and other snails. Some species consume dead and rotting organic materials while others eat live plants, especially seedlings and tender plants. Though poorly understood, some snails prefer to eat fungi and may be an important factor in dispersal of fungal spores.

Land snails are important environmental indicators and biodiversity predictors. Because of their close association with water, mollusks are good indicators of the health of the environment and may play an important role in monitoring climate change. Despite fabulous adaptations to land, snails are among the most sensitive animals to pollutants, including road runoff and acidic rainfall. Land snail populations have dwindled in recent decades, in turn contributing to the decline of some species of birds that feed on them and depend on them as sources of calcium for creating egg shells.

Quick Summary:  After signing up for your surveying location, determine which day will work best for you. You can collect during any type of weather but keep your safety in mind (read the safety plan).  Note: for the safety of the habitat, limit your team at any one site to four or fewer.

Necessary Equipment: | Clipboard | Data Sheet |Plastic /Glass Jars, and Vials |Metric Ruler (with millimeters) | Permit | Dashboard Sign | Permanent Pen |Ziplock Bags, Gallon and Sandwich Size| Magnifying Glass | Shaker Box| Gloves (garden or rubber) | Pin or Sewing Needle | Water | Paper Towel | Carrot |

Survey Time Window:  Daytime

Survey Date Window:  April 9th – June 30th

Inappropriate Weather:  Heavy rains, high winds, thunder, and lightning.

Hazards to Watch Out For: 

  • There is always the possibility of venomous snakes or black widow spiders, especially at lower elevation sites, so wearing some sort of glove and not putting hands or feet where you haven’t visually checked first is appropriate.
  • Be aware of movements of flying insects, in case there is a bee or wasp nest nearby—pick another site or work many meters away if you do find a nest of stinging insects…it is not as important as your safety.
  • Bare sticks, logs, and rocks on slopes can be slippery, especially when wet, and may be hidden by dead leaves, so watch your step.
  • The ground off trail can be irregular or have hidden holes; don’t go out of site of the trail or road.

Where to Stop:  You can selected your site(s) from the map of locations along the Parkway. There will be a brief description of location such as milepost.  You will also be able to view a satellite image online and GPS coordinates are provided.

Time for an Individual Count:  Plan for up to 2 hours at each site, you may spend longer if desired.

Collecting:  Once you’ve reached your site location, look around for habitat. Look for areas that are likely to have a supply of moisture throughout the year, for example, in deep piles of leaf litter, in depressions, under logs and on the undersides of logs, under the bark of standing or down dead trees, in cracks among rocks, and among moisture-loving plants such as ferns, also shaded areas of ravines having ample ground moisture.

Collecting Leaf Litter/Soil:  You may want to find a stick to clear away some of the leaf areas just to make sure there isn’t a snake in waiting. Grab some leaf litter and throw it into the shaker box until it is about full. Place the lid back upon the box and shake it well for about 15 seconds. The matter that passes through the screen can be emptied into your gallon size ziplock bag. Continue this process until your bag is about half full. After you’ve worked your way through the leaf litter you will then gather top soil. Scrape the top one inch of top soil of an area and place it into your other gallon ziplock bag. You may want gloves for this.

Empty Shells:  Large and more medium size shells can be placed into a cleaned food jar, plastic is preferred. Small shells can be separated into the smaller snap cap vials.  Only combine shells that are the same size so that they do not crush each other or the smaller one doesn’t disappears into the larger one.

Live Snails and Slugs:  If possible, collect live snails less than 15mm in diameter and keep them alive. This is simple: put the specimen in a sandwich ziplock bag with a wet paper towel and a small piece of a carrot. Take a small sewing needle or pin and poke a few holes in the bag. The snail or slug will be okay for at least a week. Dampen the paper towel and replace the carrot before returning the specimens to your nearest visitor center. Do not put either of the two carnivorous snails in a bag with others, but they are both usually larger than 15 mm so you would not be likely to do this.

Photos: Live snails that are 15 millimeters or larger can be identified by photographs and do not need to be collected. Each snail will need 4 images: top down, so that the whirls can be counted; buttom up, so that the umbilicus can be clearly seen; side on, so you can see down its opening; and a shot with the body back out of the shell. You will also need to photograph the length of the snail, so place your metric ruler beside it when taking the photo. Your photos can be uploaded on the Hands on the Land website.  Examples of acceptable images taken with a cell phone are below:

View of snail Tridopsis tridentata shell seen from above with ruler. View of snail Tridopsis tridentata shell seen from below with ruler. View of snail Tridopsis tridentata shell seen mouth-on with ruler.

Millipedes: Millipedes move quite slowly and many will ball up when threatened. Centipedes are faster and will bite if threated, so let the centipedes go. Millipedes have two pairs of legs on most segments while centipedes have only a single pair of legs per segment. You will likely need your magnifying glass to observe the millipede. Pick up the millipede and gently coerce the millipede to open up for you. Count the body segments and on the seventh body segment confirm the pairs of legs. If you find only one set of legs look for the gonopods (small modified set of legs used in the reproductive process) and if you find them, you have found a male. Upon identification, male millipedes are dropped into a vial with alcohol for preservation.  If you find millipedes larger than could fit in the avialable vials, just take a picture and let them go.  The attached plate of common Virginia millipedes shows types that are especially insteresting to Dr. Paul Marek of Virginia Tech, the millipede expert assisting with this project.

Photo showing male millipede (photo: Paul Marek, https://creativecommons.org/licenses/by-nc-sa/4.0/)

Record on Form: Name |Other Participants| Time Start/End |Collection Site | Elevation| Weather |Substrate │Number of Snail Specimens Collected and how many containers │ Number of Millipede Specimens Collected and how many containers │Snails/Slugs Identified and how many images taken at this stop │Description of Where You Looked (under logs, under rocks, under bark on dead snag, etc.) │

[Back at Home] Sorting Leaf Litter/Soil: Your samples need to be dried out. The easiest way to do this is to spread out your samples in an old baking pan or upon a large white paper. Let the sample site for at least a day then pick through them with a magnifying glass looking for the small specimens. Remember some snails can be only as long as a millimeter! Small shells need to be kept separate so they do not get crushed or lost in the larger ones. MAKE SURE ALL COLLECTED SNAILS HAVE A LABEL THAT INDICATES WHERE THE LEAF LITTER WAS COLLECTED AND WHEN.  Leaf litter and soil can be discarded when it is thoroughly dry and thoroughly sorted through.


Print Email

Bureau of Land ManagementUS Forest ServiceNational Park ServiceUS Fish and Wildlife ServiceEnvironmental Protection AgencyNational Oceanic & Atmospheric AdministrationDepartment of EducationNational Environmental Education Foundation
© 2001 - 2018 Hands on the Land Network