The orchids Dendrobium infundibulum and Cymbidium insigne are pollinated by the bumblebee Bombus eximius, which also pollinates the ericaceous shrub Rhododendron lyi, A study of the three plants and the bumblebee in maquis-like mountainous vegetation in northern Thailand suggests that they form a floral mimicry system with two mimics (the orchids) to one model (R. lyi). The flowers of the two orchid species offer no food reward to pollinators. Flowers of the three species show definite morphological and visual resemblance, and the species overlap to a great extent in flowering phenology and habitat Mimic flowers were much less numerous than model flowers, which occurred abundantly in the area. The rate of pollinaria removal was very low in both orchid species, resulting in a relatively small percentage of fruit set, especially in D. infundibulum. Infrequency of pollinator visits was, however, somewhat counterbalanced by long-lasting flowers. The pollinaria of the two orchid species are differently positioned on the bee, hence interference between the different reproductive systems is minimized. This is the first report which indicates floral mimicry from tropical Asia.

The sources of food and the width and overlap of the food niches of Bombus atratus and Bombus morio were determined by field observations and analysis of the pollen loads carried to the colonies by worker bees. The two species together utilized 50 flower species of which 26 were used by both. Solatium paniculatum (Solanaceae) and Psidium guajava (Myrtaceae) were the most frequently visited plants.

The food niche width and niche evenness for both species were similar. The correlation between niche width and niche evenness was non-significant showing that evenness does not depend on niche width. In addition, there was no correlation between niche width and overlap, i.e. overlap varied independently of niche width. A high overlap of food sources utilized by the two species was observed in September, October and November. This may be explained in one of two ways: (a) if B. atratus and B. morio compete for resources, competition would be more intense during those three months; (b) the convergency of both species to the same plant species (Solatium paniculatum and Psidium guajava) would only result in more intensive competition if resources were limiting. However, at that period of the year resources are abundant, therefore although the values of overlap were high, competition need not have occurred.

The bumble and cuckooo bees (Hymenoptera: Apidae: Bombini; Bombus spp. and Psithyrus spp., respectively) are important plant pollinators and any decline in numbers or species constitutes a significant threat both to biological diversity and to whole economies. The distribution, status and factors threatening all 60 known taxa (species and subspecies) of Bombini of 11 countries of Western and Central Europe (Belgium, the Netherlands, Luxembourg, Denmark, Germany, Switzerland, Austria, Czech Republic, Slovakia, Hungary, Poland) were assessed from the beginning of the 20th century. The analysis was based on a literature review, unpublished data, personal communications, our own observations, and an expert review. The IUCN Red List categories were used for assessing the threat of extinction. Eighty per cent of taxa were threatened in at least one country of the region, and 30% of taxa were threatened throughout their range in the countries considered. More species went extinct per country in the second than in the first half of the 20th century, and four taxa went extinct in all 11 countries during 1951–2000. Amongst the factors adversely affecting the Bombini anthropogenic factors (particularly those associated with large-scale farming schemes) appear to be of greater importance than natural factors. To halt population declines and species extinctions it will be necessary to preserve aspects of traditional farming practices and for all Bombini to be afforded legal protection in all countries of the region. The implementation of the European Union's Common Agricultural Policy is likely to have the greatest single impact upon pollinators in the near future.

The success of a pathogen depends not only on its transmission to new hosts, but also on its ability to colonize and persist within its current host. Studies of within-host dynamics have focused on only a few diseases of humans, whereas little is known about the factors that influence pathogen populations as they develop inside non-human hosts. Here, we investigate pathogen dynamics occurring within bumble bees (Bombus impatiens) infected by the gut trypanosome Crithidia bombi. Infection by C. bombi showed several features characteristic of vertebrate diseases, including a rapid initial increase in infection intensity, marked oscillations in parasitaemia, and the stimulation of a systemic immune response in infected bees. Within-host dynamics generated substantial variation in the infectiousness and flower-visiting behaviour of bumble bees. Changes in bee foraging that arise from infection may influence the probability of C. bombi transmission between bees at flowers.