The bees’ spontaneous preferences toward various black-and-white patterns were studied using a multiple-choice test procedure. The patterns are presented on vertical planes, and the bees’ choices at a fixed distance from the patterns are recorded. To exclude a possible influence of the bees’ previous experience with natural flowers, the bees are trained to randomized checkerboard patterns prior to testing them with sets of other patterns. We find that, when the test patterns are of the same kind, but differ in their spatial frequencies, the bees prefer low over high frequencies. However, when the patterns differ in type, the bees express, regardless of spatial frequency, a positive preference for patterns containing radiating elements, and a negative preference for patterns containing circular elements or elements arranged at random. We find, in addition, that symmetrical patterns are more attractive than less symmetrical or non-symmetrical patterns. We propose that bees respond innately to some features of natural flowers, resulting in a spontaneous preference for radiating, as well as symmetrical patterns.

Caste polymorphism, defined as the presence within a colony of two or more morphologically differentiated individuals of the same sex, is an important character of highly eusocial insects both in the Hymenoptera (ants, bees and wasps) and in the Isoptera (termites), the only two groups in the animal kingdom where highly eusocial species occur. Frequently, caste polymorphism extends beyond mere variations in size (although the extent of variations in size can be in the extreme) and is accompanied by allometric variations in certain body parts. How such polymorphism has evolved and why, in its extreme form, it is essentially restricted to the social insects are questions of obvious interest but without satisfactory answers at the present time. I present a hypothesis entitled 'genetic release followed by diversifying evolution', that provides potential answers to these questions. I argue that genetic release followed by diversifying evolution is made possible under a number of circumstances. One of them I propose is when some individuals in a species begin to rely on the indirect component of inclusive fitness while others continue to rely largely on the direct component, as workers and queens in social insects are expected to do. Thus when queens begin to rely on workers for most of the foraging, nest building and brood care, and workers begin to rely increasingly on queens to lay eggs-when queen traits and worker traits do not have to be expressed in the same individual-1 postulate the relaxation of stabilizing selection and new spurts of directional selection on both queen-trait genes and worker-trait genes (in contrasting directions) leading to caste polymorphism.

Queens and workers are not morphologically differentiated in the primitively eusocial wasp, Ropalidia marginata. Upon removal of the queen, one of the workers becomes extremely aggressive, but immediately drops her aggression if the queen is returned. If the queen is not returned, this hyper-aggressive individual, the potential queen (PQ), will develop her ovaries, lose her hyper-aggression, and become the next colony queen. Because of the non-aggressive nature of the queen, and because the PQ loses her aggression by the time she starts laying eggs, we hypothesized that regulation of worker reproduction in R. marginata is mediated by pheromones rather than by physical aggression. Based on the immediate loss of aggression by the PQ upon return of the queen, we developed a bioassay to test whether the queen's Dufour's gland is, at least, one of the sources of the queen pheromone. Macerates of the queen's Dufour's gland, but not that of the worker's Dufour's gland, mimic the queen in making the PQ decrease her aggression. We also correctly distinguished queens and workers of R. marginata nests by a discriminant function analysis based on the chemical composition of their respective Dufour's glands.