Gender Specific Brood Cells in the Solitary Bee Colletes halophilus (Hymenoptera; Colletidae)

We studied the reproductive behaviour of the solitary bee Colletes halophilus based on the variation in cell size, larval food amount and larval sex in relation to the sexual size dimorphism in this bee. Brood cells with female larvae are larger and contain more larval food than cells with males. Occasionally males are reared in female-sized cells. We conclude that a female C. halophilus in principal anticipates the sex of her offspring at the moment brood cell construction is started. Additionally a female is able to ‘change her mind’ about the sex of her offspring during a single brood cell cycle. We present a model that can predict the sex of the larvae in an early stage of development

Comparing dogs and great apes in their ability to visually track object transpositions

Knowing that objects continue to exist after disappearing from sight and tracking invisible object displacements are two basic elements of spatial cognition. The current study compares dogs and apes in an invisible transposition task. Food was hidden under one of two cups in full view of the subject. After that both cups were displaced, systematically varying two main factors, whether cups were crossed during displacement and whether the cups were substituted by the other cup or instead cups were moved to new locations. While the apes were successful in all conditions, the dogs had a strong preference to approach the location where they last saw the reward, especially if this location remained filled. In addition, dogs seem to have especial difficulties to track the reward when both containers crossed their path during displacement. These results confirm the substantial difference that exists between great apes and dogs with regard to mental representation abilities required to track the invisible displacements of objects

Larval food composition and food plants of the solitary bee Colletes halophilus (Hymenoptera: Colletidae)

Summary The pollen component of the larval food of Colletes halophilus, studied in four nature reserves in the Netherlands, was strongly dominated by Aster tripolium. The liquid component of the larval food contained high concentrations of sugars (glucose and fructose), far more than could be supplied by A. tripolium pollen present in the food. This indicates that in addition to pollen, considerable amounts of nectar were collected from this plant. The larval food showed hydrogen peroxide production. We did not, however, find this in pollen collected directly from A. tripolium flowers. We conclude that females of C. halophilus produce the enzyme glucose oxidase and add this to larval food. This is the first such finding for solitary bees. The apparent dependency of C. halophilus on A. tripolium has implications for the conservation management of this solitary bee. Composición del alimento larval y plantas alimenticias de la abeja solitaria Colletes halophilus (Hymenoptera: Colletidae) Resumen Se estudió la composición polínica del alimento larval de Colletes halophilus, en cuatro reservas naturales de los Países Bajos, encontrándose una fuerte dominancia de Aster tripolium. El líquido que compone el alimento larval contiene altas concentraciones de azúcares (glucosa y fructosa), mucho más de lo que podría ser suministrado por el polen de A. tripolium presente en el alimento. Esto indica que además de polen, una considerable cantidad de néctar fue recolectado de ésta planta. Además, el alimento larval demostró producción de peróxido de hidrógeno. Sin embargo, este componente no lo encontramos en el polen recolectado directamente de las flores de A. tripolium. Concluimos que las hembras de C. halophilus producen la enzima glucosa oxidasa y la adicionan al alimento larval, siendo éste el primer hallazgo en abejas solitarias. La aparente dependencia de C. halophilus por A. tripolium tiene implicaciones para el manejo y conservación de esta abeja solitaria