Saproxylic beetles (Coleoptera) and hoverflies (Diptera: Syrphidae) from a Mediterranean forest: towards a better understanding of their biology for species conservation

A preliminary catalogue of the Coleoptera (Hexapoda: Insecta) of the Monte Netto Regional Park (Lombardy NE Italy)

The Po Plain (Northern Italy) is one of the most urbanized areas in Europe. In such a territory, where ecosystem degradation reached critical levels and the agricultural matrix is prevailingly intensive, small fragments of hilly oak-hornbeam forests still persist. Examples of well preserved forests of the Po Plain are those of the Monte Netto Regional Park that represents irreplaceable refuges for both sedentary and migratory species. In this paper we present a preliminary list of Coleoptera inhabiting the Park collected during 10 years of field surveys using several sampling techniques (hand netting, beating tray, sight-collecting and collecting under bark; water nets; litter reducers, light traps; aerial sweet-bait trap; cross-vane panel trap, pitfall traps, Malaise traps, window traps, and walking transects). Specific samplings were also made in tree hollows and by car-netting. To date we have identified 834 species belonging to 531 genera and 71 families (several specimens and some families are still undetermined). Among all the species identified, 31 were non-native while 202 were included in the Red List of Italian saproxylic beetles, 12 of which were in threatened category. The high beetle richness and the presence of many endangered species recorded during this survey, emphasises the conservation value of Monte Netto. Moreover, the discovery of species linked to old and stable forest systems, such as Osmoderma eremita, Oxylaemus cylindricus, Pycnomerus terebrans or Xylotrechus antilope suggests how, despite their small size and the fact that they are surrounded by agricultural land, the remaining forest patches of Monte Netto still possess a fair level of naturalness, especially in the internal areas of the larger plots. Future targeted research, also intended to cover other parts of Monte Netto, could increase our present knowledge; however, and at least in the number of families, we do not expect a substantial increase in species richness.

Robber flies and hover flies (Insecta, Diptera, Asilidae and Syrphidae) in beech forests of the central Apennines: a contribution to the inventory of insect biodiversity in Italian State Nature Reserves

Background

The present paper describes a sampling-event dataset on species belonging to two families of Diptera (Syrphidae and Asilidae) collected between 2012 and 2019 in two Italian beech forests located in the central Apennines. The reference dataset consists of an annotated checklist and has been published on Zenodo. Syrphidae and Asilidae are two widespread and key ecological groups, including predator, pollinator and saproxylic species. Despite their pivotal role in both natural and man-made ecosystems, these families are still poorly known in terms of local distribution and open-access sampling-event data are rare in Italy.

New information

This open-access dataset includes 2,295 specimens for a total of 21 Asilidae and 65 Syrphidae species. Information about the collection (e.g. place, date, methods applied, collector) and the identification (e.g. species name, author, taxon ID) of the species is provided. Given the current biodiversity crisis, the publication of checklists, sampling-event data and datasets on insect communities in open-access repositories is highly recommended, as it represents the opportunity to share biodiversity information amongst different stakeholders. Moreover, such data are also a valuable source of information for nature reserve managers responsible for monitoring the conservation status of protected and endangered species and habitats and for evaluating the effects of conservation actions over time.

Combined stereomicroscope and SEM disentangle the fine morphology of the undescribed larva and puparium of the hoverfly Milesia crabroniformis (Fabricius, 1775) (Diptera: Syrphidae)

With over 80 species, Milesia Latreille, 1804 is a hoverfly genus (Diptera: Syrphidae) found in all continents except for Australia and the Antarctica. However, little is known about its life cycle and biology. The three Milesia species for which early stages are known have saproxylic larvae, suggesting that the larvae of all other Milesia species are also saproxylic. The early stages of the three Milesia species occurring in Europe are undescribed. Milesia crabroniformis (Fabricius, 1775), a mimic of the hornet Vespa crabro Linnaeus, 1758, is the largest hoverfly in Europe and is listed as Least Concern in the IUCN European Red List of Hoverflies. We here report the first early stages of Milesia ever found in Europe, describing them and their breeding sites. Larvae of M. crabroniformis were collected in water-filled tree holes of live chestnut trees (Castanea sativa Mill.) in Málaga, Southern Spain in 2020-2021. Various studies based on stereomicroscope and scanning electron microscopy (SEM) techniques have proven useful in diagnosing hoverfly early stages by observation of their fine morphology. Thus, these techniques were also used here to characterize the second (L2) and third (L3) stage larvae of M. crabroniformis, as well as the puparium. A Leica M205C binocular stereomicroscope and a Jeol JSM-ITH500HR SEM were used. The head skeleton and chaetotaxy of the L3 larva were described and illustrated. Adjustments to the diagnosis of the larvae of Milesia are proposed based on the number of hooks from the primary row of the main group of hooks. The new early stages are compared with those of other Milesia hoverflies, as well as with those of the sister group Spilomyia Meigen, 1803. The knowledge of the larval biology and breeding sites of saproxylic insects is useful for implementing forest management measures and species' conservation programs.

Catalogue, distribution, taxonomic notes, and conservation of the Western Palearctic endemic hunchback beetles (Tenebrionidae, Misolampus)

Hunchback darkling beetles of the Ibero-Maghrebian genus Misolampus Latreille, 1807 (Tenebrionidae, Stenochiinae) encompass six species: M. gibbulus (Herbst, 1799), M. goudotii Guérin-Méneville, 1834, M. lusitanicus Brême, 1842, M. ramburii Brême, 1842, M. scabricollis Graells, 1849, and M. subglaber Rosenhauer, 1856. Previously known distribution ranges of the species were delineated using many old records, the persistence of such populations being questionable under the current situation of global biodiversity loss. Additionally, the status of geographically isolated populations of the genus have been the subject of taxonomic controversy. An exhaustive bibliographical revision and field search was undertaken, and the Misolampus collection of the Museo Nacional de Ciencias Naturales (MNCN-CSIC) was revised. The aims are to (i) provide an updated geographic distribution range for the species of Misolampus; (ii) to determine the taxonomic status of controversial populations; (iii) to provide a catalogue for Misolampus; and (iv) to discuss the conservation status of these saproxylic beetles. As a result, a catalogue including synonymies and type localities, geographical records, diagnoses, and information on natural history for all species of Misolampus is presented. The results reveal that the distribution ranges of the species of Misolampus have not undergone a reduction in the last century, and indicate the presence of the genus in areas where it had never been recorded before. The morphological variability of M. goudotii drove the proposal of different taxa that are here formally synonymised as follows: M. goudotii Guérin-Méneville, 1834 = M. erichsoni Vauloger de Beaupré, 1900, syn. nov. = M. peyerimhoffi Antoine, 1926, syn. nov.

Hoverfly (Diptera: Syrphidae) assemblage of an oak-hornbeam in the Merlino Wood Natural Reserve and implications for its conservation

Merlino Wood is a typical oak–hornbeam forest in the Po Plain hydrographic region. It is one of the few remaining lowland forests in Northern Italy and is a Regional Natural Reserve and a Site of Community Interest (code IT1160010). This is the first survey on hoverflies in the study area and they act as bioindicators to assess habitat conservation. Sampling was performed with three Malaise traps and an entomological net. A total of 61 species of Syrphidae were recorded between March and October 2019. Three of the species observed are considered to be under threat in Europe, three species have been recorded for the first time in Piedmont and Heringialatitarsis (Egger, 1865) has been recorded for the first time in Northern Italy. The Syrph the Net analysis has been used to assess habitat conservation. It shows good preservation of xylosaprophagous species, while the conservation conditions of other larval trophic categories are poor.

Bacteria and Hoverflies (Diptera: Syrphidae) in Tree Hollows From the Iberian Mediterranean Forest

Saproxylic insect communities inhabiting tree hollows in Mediterranean forests depend on a combination of physical characteristics and interactions occurring between community member species. Despite the need to preserve these organisms, little is known about their interrelationships, in particular those relationships between saproxylic insects and microbiota occurring in these microhabitats. In tree hollows of Quercus rotundifolia Lamark that hold water and contain dead leaves, abundant microbial populations can be found. Developing on them are the larvae of Mallota dusmeti Andréu, 1926 (Diptera: Syrphidae), a vulnerable species (IUCN category: Marcos-García and Quinto 2011). This study provides the first data on the microbiota living inside the gut of the larvae of M. dusmeti, as well as the microbiota in the hollow where these larvae develop. Bacteria were identified by amplification and partial sequencing of the V1-V3 regions and the complete nucleotide sequence of 16S rRNA genes. We found eight species of bacteria living in tree hollows and three species in the gut of M. dusmeti larvae: Bacillus cereus, Bacillus toyonensis, and Lysinibacillus sphaericus. The filter-feeding mechanism characteristic of M. dusmeti larvae is selective in enabling ingestion of bacteria only above 2.1 µm in diameter.

Facilitation among saproxylic insects inhabiting tree hollows in a Mediterranean forest: the case of cetonids (Coleoptera: Cetoniidae) and syrphids (Diptera: Syrphidae)

Tree hollows offer an ideal niche for saproxylic insects in mature Mediterranean forests, where Diptera and Coleoptera are the richest groups. Co-occurrence is frequently observed among many species of both groups in these microhabitats, and some of these species have been considered to facilitate the presence of other species by acting as ecosystem engineers. One of the systems that is found in Mediterranean tree hollows is formed by cetonid (Coleoptera: Cetoniidae) and syrphid (Diptera: Syrphidae) larvae. Here, cetonid larvae feed on wood and litter and produce a substrate that is easier to decompose. To assess the possible role of these larvae as facilitating agents for the saproxylic guild, we studied whether the presence of saprophagous Syrphidae inside tree hollows is associated with the activity of cetonid larvae. Furthermore, in laboratory conditions, we tested whether cetonid larvae activity can improve the development and fitness of the saprophagous syrphid species. Our results show that "cetonid activity" was the variable that best explained the presence of saprophagous syrphid species in natural conditions. Myathropa florea (L., 1758) was one of the species most influenced by this activity. The laboratory experiment gave similar results, demonstrating that an enriched substrate with Cetonia aurataeformis Curti, 1913 larval feces improves syrphid larval growth rate and fitness of adults (measured as longer wing length) of M. florea.