and octyl acetate, scents differed among populations. Similarly, there were strong differences in flower visitor spectra among populations with most abundant flower visitors being bees and syrphid flies at low and high altitudes, respectively. Pollinator climate differed also among populations; however, independent of altitude, most pollinators were bees of Lasioglossum, Andrena, and Nomada. Only few syrphids acted as pollinators and this is the first record of flies as pollinators in C. calceolus. The electrophysiological tests showed that bees and syrphid flies sensed many of the compounds released by the flowers, among them linalool and octyl acetate. Overall, we found that both floral scent and visitor/pollinator climate differ among populations. We discuss whether interpopulation variation in scent is a result of pollinator-mediated selection.

There is growing interest in the vertical stratification of forest biodiversity, but little is known about this aspect for Syrphidae living in forests. For this study, seven Malaise traps were suspended in the canopy and seven were placed on the ground, in a lowland forest in northern Italy. Altogether, 868 specimens of Syrphidae were collected; 229 from the canopy and 639 from the ground, comprising a total of 53 species. Three species [(Ceriana conopsoides (Linnaeus), Eupeodes corollae (Fabricius), Psilota atra Fallén)] were associated significantly with the canopy layer, and seven species [(Brachypalpoides lentus (Meigen), Chalcosyrphus nemorum (Fabricius), Chrysotoxum cautum (Harris), Eumerus flavitarsis Zetterstedt, Helophilus pendulus (Linnaeus), Myathropa florea (Linnaeus) and Xylota segnis (Linnaeus)] with the ground level. The sex‐ratio of the Syrphidae differed significantly between the two layers, as females were caught mainly at ground level, while males were caught preferentially in the canopy. Species with saprophagous and saproxylic larvae were caught more commonly at ground level. Species richness declined from April to November but vertical stratification was constant for most of the season. Multivariate analyses showed that two factors were correlated significantly with the community composition of Syrphidae: height of Malaise trap and estimated age of dominant trees.

The West-Palaearctic cerioidines (Syrphidae: Cerioidini) are revised, including species of the genera Ceriana Rafinesque, Primocerioides Shannon, and Sphiximorpha Rondani. Three new species are described, Ceriana glaebosa van Steenis & Ricarte sp. n. (Cyprus), Ceriana media van Steenis & Ricarte sp. n. (Afghanistan and Iran) and Ceriana skevingtoni van Steenis & Ricarte sp. n. (Armenia, Azerbaijan and Iran). The following names are proposed as junior synonyms: Cerioides caucasicus Paramonov, 1927 [= Ceriana conopsoides (Linnaeus, 1758)], Ceria binominata Verrall, 1901 [= Sphiximorpha garibaldii (Rondani, 1860)], Ceriana worelli, Brădescu, 1972b [= Sphiximorpha garibaldii (Rondani, 1860)] and Sphiximorpha hiemalis Ricarte, Nedeljković & Hancock, 2012 [= Primocerioides regale Violovitsh, 1985]. Identification keys, biological data and distribution maps for the studied taxa are provided. Conops vaginicornis Schrank, 1803 is discarded as a synonym of Ceriana conopsoides and should be considered as nomen dubium.

As predator and parasitoid insects depend on multiple resources for adult feeding and reproduction, environmental heterogeneity (EH) is expected to be a key driver of their species diversity. In temperate regions, the benefits of EH are expected to vary across spatial scales and seasons, depending on species life‐history traits and temporal fluctuations in resources. We tested the importance of EH at multiple spatial scales on diversity and abundance of predator and parasitoid insects, and whether its effects changed across seasons. Insect sampling was carried out in highly fragmented landscapes in a Mediterranean region (Tuscany, Central Italy). We selected 18 semi‐natural patches, embedded in an intensive agricultural matrix. For each patch, EH was measured at three spatial scales (micro, patch, and landscape). Five groups of predator and parasitoid insects were sampled 16 times with pan traps between March and November, 2012. EH at the landscape scale positively influenced the diversity of predator and parasitoid insects, while the effects at smaller spatial scales were less evident. The strength and the direction of EH˗diversity relationship changed between groups and across seasons, indicating that the mechanisms by which EH affects predators and parasitoids are various and complex. Conservation strategies aimed at maximising the diversity of predators and parasitoids should focus more on increasing EH at the landscape scale than at the local scale.

Abstract. In this study we analyzed the inter-specific relationships in assemblages of syrphids at a site in northern Italy in order to determine whether there are patterns in diurnal co-occurrence. We adopted a null model approach and calculated two co-occurrence metrics, the C-score and variance ratio (V-ratio), both for the total catch and of the morning (8:00-13:00) and afternoon (13:00-18:00) catches separately, and for males and females. We recorded discordant species richness, abundance and co-occurrence patterns in the samples collected. Higher species richness and abundance were recorded in the morning, when the assemblage had an aggregated structure, which agrees with previous findings on communities of invertebrate primary consumers. A segregated pattern of co-occurrence was recorded in the afternoon, when fewer species and individuals were collected. The pattern recorded is likely to be caused by a number of factors, such as a greater availability of food in the morning, prevalence of hot and dry conditions in the early afternoon, which are unfavourable for hoverflies, and possibly competition with other pollinators. Our results indicate that restricting community studies to a particular time of day will result in certain species and/or species interactions not being recorded. 649* Present and corresponding address: