Abstract:
Conflicts over reproductive division of labour are common in social insects. These conflicts are often resolved via antagonistic actions
that are mediated by chemical cues. Dominant egg layers and their eggs can be recognized by a specific yet similar cuticular hydrocarbon
profile. In the facultatively queenless ant Gnamptogenys striatula, a worker’s cuticular hydrocarbon profile signals its fertility and this
determines its position in the reproductive division of labour. How eggs acquire the same hydrocarbon profile is as yet unclear. Here, we
search for glandular sources of egg hydrocarbons and identify the putative mechanism of egg marking. We found that eggs carry the
same hydrocarbons as the cuticle of fertile workers, and that these hydrocarbons also occur in the ovaries and the haemolymph. None of
the studied glands (Dufour, venom, labial and mandibular gland) contained these hydrocarbons. Our results indicate that hydrocarbons
are deposited on eggs while still in the ovaries. The low hydrocarbon concentration in the ovaries, however, suggests they are produced
elsewhere and transported through the haemolymph. We also found that fertile workers regularly deposit new hydrocarbons on eggs by
rubbing laid eggs with a hairy structure on the abdominal tip from which a non-polar substance is secreted.
