CLUSTERING EXPERIMENT: BNU, 30-31 OCT 2013


Animal: ants (Terramorium, Caespitum, Linnaeus 1758)

CELL no 2 S=(2.6dm x 2.7dm)=7.0dm2 ->  38 ants -> density= 5.4/sq.decimeter
CELL no 5 S=(1.5dm x 2.7dm)=4.0dm2 -> 229 ants -> density=57.2/sq.decimeter 

The numbers of ants were counted on the screen (after zooming in)

The strips of paper between the cells are impregnated with citronella oil
which is a well-known repellant for ants (as well as mosquitos). However, in the
course of time over a time interval of several hours some ants will
nevertheless cross to
other cells (mainly to cell 8). 
The advantage of these strips over a more rigid container is that the ants 
will mostly stay away from
them whereas they will tend to move to the edge of a container where they will 
then remain. 

What we call a mini-cluster is a a group of at least 3 ants which stay together
for more than one minute.

In this experiment a picture was taken automatically every minute
thanks to a timer
(Viltrox) connected to a camera (Sony: alpha,200). However, after
about 5 hours, as there
were few changes, the rate was reduced to one picture every 10 mn. Altogether,
872 photos were taken.

Objective:
We wish to do a long-duration observation showing not only
how the clusters appear (which is a matter of one or two hours) but also
how they disappear (which can take many hours).
That is why the observation almost covered a 24 hour period.
Whereas some smaller clusters indeed disappeared after several hours,
the main cluster was still present when the experiment was stopped.
Needless to say, it would be very time consuming and probably fairly
useless to let all experiments last so long. In the following experiments 
we will be foremost interested in the formation of the clusters.

Summary: 
After the ants were transferred from their container to the cells, they 
moved faster than usual but some 20mn after the start of the experiment they slow down
and some short-lived min-clusters start to appear in the high density cell (f2).
30mn : Two more permanent clusters take shape (f3)
2h40 : Whereas there had been no mini-clusters in the low-density cell, a mini-cluster takes shape (f7)
7h40 : The smallest of the two clusters in the high density cell disappears (f12).
9h40 : The mini-cluster in the low density cell has disappeared (f15).
       As a result there is only
       one remaining cluster and it will stay until the experiment is ended almost 12 hours   
       after it started (f19).

Chronology:
f1  ->  9:56 -> Start
f2  -> 10:26 -> Formation of the first mini-clusters in cell 5; they are fairly unstable
f3  -> 10:36 -> Two clusters in cell 5 become more permanent; no cluster in cell 2
f4  -> 10:46 -> same
f5  -> 12:16 -> Little by little the two clusters of cell 5 have become bigger
f6  -> 12:56 -> A mini-cluster takes shape in cell 2
f7  -> 13:36 -> The smallest of the two clusters in cell 5 shrinks
f8  -> 15:32 -> The cluster of cell 2 almost disappears (last image of S1=1 image/mn)
f9  -> 15:50 -> The mini-cluster of cell 2 reappears (first image of S2=1 image/10mn)
f10 -> 16:30 -> The small cluster of cell 5 continues to shrink
f11 -> 17:10 -> same
f12 -> 17:30 -> End of the small cluster of cell 5
f13 -> 17:50 -> same
f14 -> 18:30 -> The cluster of cell 2 has almost disappeared
f15 -> 19:10 -> same
f16 -> 20:50 -> There remains only one cluster
f19 -> 08:40 (next day) -> The same cluster remains albeit somewhat smaller (because of the leaks); the
                            experiment is stopped