Adaptive behaviour of honeybees (Apis mellifera) toward beetle invaders exhibiting various levels of colony integration

Social bees generally host fewer nest invaders than do ants and termites. This is potentially explained by the adaptive defensive strategies of host bees when faced with nest invaders exhibiting various levels of colony integration (based on adaptations to the nest habitat and frequency of nest inhabitation). In the present study, experiments are performed to determine the behaviour at the nest entrance of European honeybee guards Apis mellifera L. (Hymenoptera: Apidae) toward beetle invaders of various levels of behavioural integration into colonies. The species used to test this include Aethina tumida Murray (Coleoptera: Nitidulidae), which is regarded as a highly integrated, unwelcome guest (synechthran) or true guest (symphile); Lobiopa insularis Laporte (Coleoptera: Nitidulidae) and Epuraea luteola Erichson (Coleoptera: Nitidulidae) that are accidentals; and Carpophilus humeralis Fabricius (Coleoptera: Nitidulidae), Carpophilus hemipterus L. (Coleoptera: Nitidulidae) and Tribolium castaneum Herbst (Coleoptera: Tenebrionidae), all of which are species that are not integrated into honeybee colonies. The responses of guard bees to a control bead also are noted. In general, bees ignore T. castaneum and E. luteola to a greater extent than other beetle species. Bees make contact with the black glass bead (a non‐aggressive behaviour) more than they do all beetle species. Bees treat A. tumida more defensively than they treat any other beetle species and the level of bee defensiveness varies by colony. These data suggest an adaptive heightened defensive response by bees toward the most integrated colony intruder but a significantly reduced level of response toward invaders representing all other levels of colony integration.     

Ecogeographical patterns in the incidence of brood parasitism in bees

The percentage of cleptoparasitic species in a fauna of Apoidea decreases from 25–30% at high latitudes to 10–15% in the subtropics. We argue that this pattern should not be explained by an allegedly stronger seasonality at higher latitudes (that would enable parasites to better synchronize with their hosts), but rather by the unpredictability of the climate, and concomitantly host phenology and population size, in (sub)arid climates.     

Temperature gradient chambers for research on global environment change. II. A twin-wall tunnel system for low-stature, field-grown crops using a split heat pump

A temperature gradient chamber (TGC) is described which enables elevated CO₂ concentrations and a dynamic temperature gradient to be imposed on field crops throughout their life cycle under standard husbandry. Air is circulated through two double-walled polyethylene-covered tunnels connected to a split heat pump system to give a near-linear temperature gradient along each tunnel. Solar energy gain along each tunnel and exchange with outer tunnel air flow contribute to the temperature gradient and also produce diurnal and seasonal temperature fluctuations corresponding to ambient conditions. Mean temperature gradients of between 3 and 5°C have been recorded throughout the growing seasons of crops of lettuce, carrot, cauliflower and winter wheat. Elevated or present CO₂ concentrations are maintained in each of two pairs of tunnels throughout the cropping season using pure CO₂ injected through motorized needle valves. This system can realistically simulate aspects of the effects of projected future environmental change on crop growth, development and yield, and in particular tin-possible interaction of the effects of increased CO₂ and temperature.     

Black tea manufacture.

A comparison of the structure of the leaf manufactured by different processing systems has been made by transmission and scanning electron microscopy. A single harvest of clonal leaf was divided into batches and commercially manufactured by Orthodox, Rotorvane only, Rotorvane combined with Cutting, Tearing and Curling and the Lowrie Tea Processor methods. The different manufactures produced leaf with characteristically different damage patterns. The relationship of the different forms of damage to the qualities of made tea is discussed.     

Root and shoot growth of semi-dwarf and taller winter wheats

Investigations are reported of root and shoot growth in semi-dwarf and taller winter wheat varieties grown in contrasting soils over three years. Comparisons were made of the distribution with depth of roots, estimated by injecting rubidium-86 into stem bases and counting the content in soil cores. The relative ability to absorb phosphate from different zones was measured from the recovery in aerial parts of ³²P injected into the soil at different depths. The distribution of dry matter in roots and aerial parts, and total root length, was measured using soil cores and samples of aerial parts taken during the growth of the crop. Relative growth rates of the aerial parts followed a sigmoid curve, but those of the roots showed little change between germination and anthesis. There was little evidence of varietal differences in root growth, though there was some indication that at depth the roots of the semi-dwarf varieties were more extensive and absorbed more phosphate than those of the taller varieties.