Ant queen pheromones (QPs) have long been known to affect colony functioning. In many species, QPs affect important reproductive functions such as diploid larvae sexualization and egg-laying by workers, unmated queens (gynes), or other queens. Until the 1990s, these effects were generally viewed to be the result of queen manipulation through the use of coercive or dishonest signals.

The evolution of honest animal communication is mostly understood through the handicap principle, which is intrinsically dependent on the concept of individual quality: low-quality individuals are prevented from producing high-quality signals because if they did so, they would pay greater production costs than high-quality individuals. Here, an alternative explanation is tested for the black bib size of male house sparrows Passer domesticus, an honest signal of quality whose expression is...

Colour patterns, e.g. irregular, spotted or barred forms, are widespread in the animal kingdom, yet their potential role as signals of quality has been mostly neglected. However, a review of the published literature reveals that pattern itself is a promising signal of individual quality across species of many different taxa.

The carotenoid-based ornaments displayed by many birds often play key roles in social and sexual signalling, revealing information about individual quality. Understanding the mechanisms of coloured trait production and maintenance requires an accurate description of their composition and of the physiological pathways involved in their expression. Carotenoid-based colouration has been extensively studied in birds, but such information is often lacking for coloured integuments other than...