Questions? Ask:
Jovel Queirolo: jovelq@stanford.edu
Evie Pless: epless@stanford.edu
Daniel Washington: danwashi@stanford.edu
Charlotte Wayne: crwayne@stanford.edu
Deborah Gordon: dmgordon@stanford.edu
Due dates: All data for all 3 treatments should be entered by April 29. The spreadsheet for entering data is at: https://docs.google.com/spreadsheet/ccc?key=0Ar5PBZeWiCeJdENBYkxLM0hHTj
U4VVRFREhZNjlhbXc#gid=1 . YOU SHOULD MAKE A NEW SHEET, AND LABEL THAT
SHEET WITH YOUR GROUP NUMBER. Complete data analysis and group reports due in class on May 6. The rubric for group reports will be posted on Coursework.
How Argentine ant trail networks expand
Argentine ant colonies consist of many nests, linked by trails of ants. This system of nests linked by trails can be considered to be a network.
A colony’s network of nests and trails changes on a seasonal cycle. In the winter, when it is cold and wet, the network coalesces into one or a few very large nests and the ants do not do much foraging for food. Over the spring, the network expands, reaching its fullest range of about 200 square meters per colony at the end of the summer, in September. Once it begins to turn cool and to rain in October and
November, the network begins to retract again. In April, when we are doing this project, the network is expanding.
The project will investigate how Argentine ant colonies add to the network of trails and nests. It is not known whether a colony is more likely to expand to reach a food source or a new nest.
Our experiment will test whether a new trail is more likely to form in response to a food bait or to a new nest site. Previous work shows that the further a bait is placed from a trail, the less likely are the ants to reach it.
Here’s the most important thing you need to know about this project: Don’t enter any data unless you are certain the numbers are correct! If you don’t
know what to do, ask. There is no answer you are supposed to get – the objective is to find out what the ants will do. If the data are reliable we will be able to answer a question about Argentine ant colony networks.
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1. Find ants
Argentine ants tend to travel along edges in paving stones and sidewalks.
They are the most abundant small ants on campus, but you may see ants of other species as well. A guide to the most common ants on campus is included on
Coursework. Print out the metric ruler so you can measure the ants you find, to help determine if they are Argentine ants.
Argentine ants move nests often and they don’t make a very impressive or elaborate nest. Sometimes a nest has a tiny pile of excavated soil around it, but often the ants go into a plain hole in the ground. If you see ants go into the ground, you can call it a nest.
Use one of the many free GPS apps to record the coordinates of the nests you find and report them in the Google doc at https://docs.google.com/spreadsheet/ccc?key=0AuKlWkmSZscQdGtOaXZGU0JsT3V zbC1lVHROa0NOQnc#gid=0
A link to this spreadsheet will be viewable from Coursework as well.
Your group’s site should be at least 20 m from a site used by another group.
Use the Google map, as well as the tape measure in your kit, to ensure that your nest is at least 20m from other groups.
2. Map and photograph the trails
Use your tape measure and graph paper to map at least two nests and trails between them. The map should be good enough for you to figure out the next day if the trails are the same.
Take a photo of the trail between the nests.
You will be testing what causes the ants to form a new trail off of this trail.
3. Making the food baits and nest sites
Your group will receive a kit containing:
 4 Tubes
 2 Transfer pipets (one for sugar water, one for plain water)
 Measuring tape
 Food coloring
 Masking tape (for labeling)
 Cotton balls
 Forceps (they look like giant tweezers)
 Flags
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Note: You can find hot water and sugar on your own (dining halls, campus cafes)
Food baits will consist of sugar water, which should be 1 part sugar, 2 parts
water, in a tube with a cotton ball. Nest sites will be tubes with plain water and cotton ball, to create a humid environment, wrapped in aluminum foil so that it is dark.
To make a food tube, you will need to get some hot water. Make the sugar solution in a separate container and fill the tube about ¾ full. Push the cotton ball into your tube using your forceps. If there are air bubbles, push the cotton ball all the way down until you’ve pushed all the air out. You don’t want any air bubbles below the cotton ball.
Pour a little more sugar water on top of the cotton so it smells enticing to passing ants.
To make the nest sites, use plain water, not sugar water, in a tube plugged with cotton in the same way. Then wrap the outside of the tube in foil so it will be dark inside. Leave the end of the tube open so the ants can get in!
For Day 3, you will need to add food coloring to one of the tubes with sugar water. To do this, pick up your tube, shake off a few ants if there are a lot of them, gently pull the cotton ball out, add a generous squirt of food coloring (about 5-10 drops with your pipette, more is better than less) and replace your cotton ball – making sure there is no air under your cotton ball. Your solution should be dark red.
When you come back and the ants have enjoyed your red sugar water, they will have a red tint to them.
Ants communicate with chemicals, so any odorous substance on your fingers will be a big deal for the ants that encounter the tube. Wash your hands before working with tubes and try not to touch the opening of the tube. You may wear plastic gloves.
4. Sequence of treatments:
Thus sometime in the 17 days between April 6 and April 22, your group should do the 3 treatments, and there must be at least 2 days between 1 and 2, and between 2 and 3.
There are 3 treatments. Each one takes 3 days.
Your group should do all 3 treatments, each separated by at least 2 days.
The treatments will be done in a different sequence by each segment of the class. This controls for differences in the response of ants to nest sites and baits, depending on changes in the weather over those 17 days. If all groups did the treatments in the same sequence, then we would not know whether the difference in treatments was due to a change in weather.
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There are 3 treatments (1,2,3). Your group has a number. Your group will be assigned to one of 3 clusters (A, B, C). Each cluster will be asked to do the 3 treatments in a different sequence:
1st
SEQUENCE
2nd 3rd
CLUSTER
A
B
C
5. What to do
1
2
3
2
3
1
3
1
2
On a hot day the ants may not be active in the middle of the day. Argentine ants will not recruit to bait or nest sites in bright sunlight, so choose places with some shade at least part of the day.
The attached diagram shows the 3 treatments.
Near = 0.3 m, Far = 0.6 m
This measurement is the distance from the trail.
All tubes should be at least 1.5 m, ideally 2 m from each other
For all 3 treatments the procedure is:
1) Day 1
Map the trails at the site. Use graph paper and use the tape measure to record distances between nests.
Put out food and/or nest tubes at the site. Mark with flags. Check overnight to make sure they are still in place – if they disappear, replace them.
2) Day 2
Check map. If there are no changes, record this. If there are changes, make a new map that notes any changes in the trails.
Make counts at the food tubes:
Imagine a line that connects the trail to the food tube, perpendicular to the trail.
Count the ants as they pass a line, in either direction, along this line, for 1 minute.
Make 3 counts for each tube.
Enter the numbers in the spreadsheet.
Look inside the nest tube and note whether it is occupied.
Put out the next set of tubes.
3) Day 3
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Two hours before counting, put food coloring in the food tubes.
Check map and note any changes in the trails
Make counts at the food tubes as above.
Look inside the nest tube and note whether it is occupied.
Follow 5 marked ants that leave the food and note where they go – back to the old trail or to a new nest?
Take all the stuff away and clean it out so that it will be dry and ready to go for the next trial.
Data analysis will ask:
Comparing the results for treatment 1 and 2:
Does the nest site make it more likely that the trail will extend to the food?
Comparing 1,2 with 3:
Are the ants more likely to go from food to a nest or from a nest to food?
Tips:
 Hide the tubes somewhere discreet or use flags marked, "Experiment in progress -- Please do not disturb."
On Days 2 and 3, you may want to check the baits several times over the course of the afternoon and perform the counts when there are ants
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