Interspecific interactions in solitary Aculeata - is the presence of heterospecifics important for females establishing nests?

There are several possible causes of aggregated nesting in solitary Aculeata, one being joint defense against parasites. We tested whether females prefer nesting in aggregations, even if they consist of heterospecifics. We compared the colonization and nesting parasitism of trap-nests with and without a red mason bee aggregation. The results did not support our hypothesis that females prefer nesting in aggregations. The numbers of wild Aculeata nests did not differ between trap-nests with and without an aggregation. Unexpectedly, parasitism rates were higher in trap-nests with aggregations. When analyzing only nests of wild insects (mostly wasps), the differences in parasitism disappeared. Natural nesting sites may be such a limited resource that females nested in the first trap-nest they encountered and did not discriminate between our treatments, or wasps might share too few parasites species with bees to benefit from joint nest defense.

Secretions of mandibular glands are not involved in the elicitation of rescue behaviour in Formica cinerea ants.

Certain ants perform rescue behaviour for other ants that require help, and the expression of rescue behaviour is hypothesized to depend on signals ("calls for help") sent by the imperilled individuals. We studied whether the mandibular glands were involved in the elicitation of rescue behaviour in Formica cinerea Mayr ants. In the first experiment, we determined the occurrence and characteristics of rescue behaviour directed towards nest mates with impaired mandibular gland communication. We did not observe any difference in rescue behaviour directed towards individuals who were untreated, treated with paint over the mandibles, or sham-treated with paint over the thorax. In the second experiment, we determined whether rescue behaviour would occur towards dummy ants coated with the contents of the mandibular glands. Compared with the control untreated nest mates, we found that rescue behaviour was not directed towards either the untreated dummy ants or the dummy ants covered with crushed mandibular glands. Our results indicated that the "call for help" signal does not originate from the mandibular glands. Therefore, we propose that gaster-tip glands represent a plausible alternative source of rescue-eliciting pheromone(s) for the F. cinerea ants examined in this study.

The influence of trimethylamine on the concentration/odour intensity relations in hexanal.

Hexanal and trimethylamine are products formed in the process of fish deterioration and it is believed that both these substances contribute somehow to the typical off-flavour developing in the course of this process. In aqueous hexanal solutions and in hexanal solutions with added trimethylamine the intensity differences in the odour of hexanal and the difference thresholds for hexanal solutions were determined.

Odour intensity and taste acceptability of spices in minced fish products.

Minced fish products, like pastes, sausages and hamburgers, usually are produced with the addition of spices, and the amount of the individual flavouring ingredients is chosen hitherto on basis of the trial and error method. A more efficient approach, based on predictor equations, is described in this paper.