Pollinator activity and flowering in agricultural weeds in Sweden.

The extent to which weeds in arable land are useful to pollinators depends in part on the temporal pattern of flowering and insect flight activity. We compiled citizen science data on 54 bees and hoverflies typical of agricultural areas in southern Sweden, as well as 24 flowering weed species classified as pollinator-friendly in the sense that they provide nectar and/or pollen to pollinators. The flight periods of the bees and hoverflies varied greatly, but there were also some consistent differences between the four groups studied. The first group to fly were the early flying solitary bees (7 species), followed by the social bees (18 species). In contrast, other solitary bees (11 species) and hoverflies (22 species) flew later in the summer. Solitary bees had the shortest flight periods, while social bees and hoverflies had longer flight periods. Flowering of weed species also varied greatly between species, with weeds classified as winter annuals (e.g., germinating in autumn) starting early together with germination generalists (species that can germinate in both autumn and spring). Summer annuals (spring germinators) and perennials started flowering about a month later. Germination generalists had a much longer flowering period than the others. Weekly pollinator records were in most cases significantly explained by weed records. Apart from early flying solitary bees, all models showed strong positive relationships. The overall best explanatory variable was the total number of weeds, with a weight assigned to each species based on its potential as a nectar/pollen source. This suggests that agricultural weeds in Sweden provide a continuous potential supply of nectar and pollen throughout the flight season of most pollinators.

How does viewing angle affect the perceived accuracy of Batesian mimicry in hoverflies?

Despite Batesian mimicry often eliciting predator avoidance, many Batesian mimics, such as some species of hoverfly (Syrphidae), are considered to have an "imperfect" resemblance to their model. One possible explanation for the persistence of apparently imperfect mimicry is that human perceptions of mimicry are different from those of natural predators. Natural predators of hoverflies have different visual and cognitive systems from humans, and they may encounter mimics in a different way. For example, whilst humans often encounter hoverflies at rest on vegetation, or in photographs or textbooks, where they are typically viewed from above, natural predators may approach hoverflies from the side or below. To test how viewing angle affects the perception of mimicry, images of mimetic hoverflies and their models (wasps and bees) were shown from different angles in an online survey. Participants were asked to distinguish between the images of models and mimics. The results show that the viewing angle does affect perceived mimicry in some species, although it does not provide a complete explanation for the persistence of imperfect mimicry in nature. The effect is also highly species-specific. This suggests that to understand better how selection has shaped mimetic accuracy in hoverflies and other taxa, further study is required of the viewing angles that predators utilize most commonly in nature.

Hoverflies of the Timon-David collection (Diptera, Syrphidae).

Background: Hoverflies are among the most important insect pollinators and there is documented evidence of a recent decline in their populations. To trace the past distributions of hoverfly species, verified records of historical collections are essential. New information: Here, we provide data on 1071 specimens of hoverflies collected or received by Jean Timon-David and hosted at the Marseille Natural History Museum, France. Most of the specimens were collected by Timon-David himself and come from south-eastern France, mainly from the Departments of Bouches-du-Rhône, Var and Hautes-Alpes. Most of these specimens were checked for the accuracy of their identification according to the latest identification keys. This resulted in 85 additions to the known fauna of the French Departments, mostly for Var and Bouches-du-Rhône. The taxonomy of all specimens was checked against the latest available checklists and updated names added whenever necessary. Specimens received from entomologists working in other continents may also be valuable, as these are historic testimonies of the fauna of their own respective regions of origin and may, therefore, also be used as reference material. One paratype specimen from Australia is present in the collection. The holotype of Cheilosia vangaveri Timon-David, 1937 is absent from the collection and should be considered as lost. All but two of the specimens with locality labels had their geographical coordinates of origin added in the dataset.

Spatiotemporal analysis of distribution of pest and predator in corn crops

Crop pests have negative impacts on yield. This paper proposes a spatiotemporal geostatistical modeling to compare data of adult Syrphidae fly count and corn leaf aphid Rhopalosiphum maidis (Fitch, 1856) colonies in corn crops. The use of a geostatistical model that allows the space-time variation makes the approach more interesting because it is a more complete model. Multiple regression was used to model the trend component for the variable response adult Syrphidae fly count and corn leaf aphid colonies, with the coordinates serving as covariates and the spatiotemporal variations around the deviation are described by a random spacetime residual field. Finally, the prediction map obtained by kriging may be a biological indicator of possible corn leaf aphid colonies in the corn crop. It was possible to verify that the occurrence of the pest provided a significant increase in adult predators and seminatural habitats may favor populations of natural enemies.

Descrição da fêmea, genitália do macho e larva de Ocyptamos sativus (Curran, 1941) (Diptera: Syrphidae) / Description of the female, male genital apparatus and larva of Ocyptamus sativus (Curan, 1941) (Diptera: Syrphidae)

The female, male genital apparatus and larva of Ocyptamus sativus are described. A short report of the predatory habits of this species is made.