2.3 ǀ Colony maintenance
Individual life pairs of a carrying worker and a carried female sexual
were kept in 1.5 ml Eppendorf tubes with moist cotton and fed with
cookie crumbs. After transfer to the laboratory, we added to each of 43
female sexuals one to three unrelated males from laboratory stock
colonies (one male to 16, two males to 13, and three males to 14 female
sexuals). Additional 112 female sexuals were left without the chance to
mate with additional males. One day later, the males were removed and
the female sexuals were individually placed into 94mm x 16mm Petri
dishes divided by a separator into two equal halves. One half of the
dish was filled with plaster with small tunnels and two or three small
chambers serving as the nest, the other served as a foraging arena, into
which we added a droplet of honey, dead Drosophila or chopped up
cockroaches twice per week. To allow the ants to move from the nest to
the foraging arena we made a 5mm wide hole in the plastic separator
using a soldering iron. The nesting chambers were covered by red plastic
foil. To more closely mimic the architecture of natural nests the Petri
Dishes were kept vertically by attaching them to a plaster base.
Experimental nests were kept in incubators under near-natural artificial
conditions matching those found at the collecting site (i.e., from June
to September at summer temperatures of 17°C – 34°C, slowly changing by
a weekly temperature decrease of up to 4°C to 5°C – 13°C in December to
March). Offspring production of isolated female sexuals was recorded
every week for a total of 40 weeks. In addition, we observed offspring
production from similarly housed lab-reared female sexuals, which had
had only access to brothers. These latter colonies were kept alive only
for three months after the hibernation. Note here that we use “female
sexuals” even for individuals that have mated and began laying eggs and
which would conventionally be referred to as “queens.” However, as
many data refer to both mated, fertile and virgin, non-fertile
individuals, using both terms would have made the text difficult to
read.
In addition to the population genetics software mentioned above,
statistical analyses were done with R 4.0.3 (R Core Team 2020) and
Statistica 6.0 (StatSoft, Tulsa, OK).