Subarctic vegetation is composed of mountain birch [Betula pubescens ssp. czerepanovii (MB)] forests with shrubs and other species growing in the understorey. The effects of the presence and density of one understorey shrub, Rhododendron tomentosum (RT), on the volatile emissions of MB, were investigated in a Finnish subarctic forest site in early and late growing season. Only MB trees with an RT-understorey emitted the RT-specific sesquiterpenoids, palustrol, ledol and aromadendrene. Myrcene, which is the most abundant RT-monoterpene was also emitted in higher quantities by MB trees with an RT-understorey. The effect of RT understorey density on the recovery of RT compounds from MB branches was evident only during the late season when sampling temperature, as well as RT emissions, were higher. MB sesquiterpene and total emission rates decreased from early season to late season, while monoterpene emission rate increased. Both RT and MB terpenoid emission rates were linked to density of foliar glandular trichomes, which deteriorated over the season on MB leaves and emerged with new leaves in the late season in RT. We show that sesquiterpene and monoterpene compounds emitted by understorey vegetation are adsorbed and re-released by MB, strongly affecting the MB volatile emission profile.

We examined the effects of diet mixture on the nymphal performance of a polyphagous grasshopper Parapodisma subastris Huang by developing the first-stadium nymphs with either single or various combinations of plants occurring in their natural habitat. Intrinsic quality in terms of nymphal survival differed largely across the 16 plant species. However, even combinations of the six worst quality plants (survival 10% or less in each) greatly improved nymphal survival when compared to that of superior quality plants (more than 70% survival). In contrast, the addition of either of two inferior plants (more than 10% and less than 40% survival) to the superior plant affected neither the survival nor the adult mass. Thus, diet mixture can be particularly important when only low quality plants are available. The adaptive significance of diet mixture was discussed in relation to the habitat flora and foraging habits of the grasshopper in the present study.

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A mediastinal thoracic duct cyst was incidentally found in an asymptomatic 45-year-old man. The cyst, 6 cm in diameter, was soft and unilocular, with an extremely thin wall, and contained chyle. It was successfully excised.