The genera Eumerus and Merodon (Diptera: Syrphidae) have a high taxonomic diversity (300+ species altogether), but life histories of most species are unknown. In addition, these hoverfly genera are recognised to be pests (ornamental plants and vegetable crops). In this paper, early stages of four hoverfly species are described, Eumerus hungaricus Szilády, 1940, Eumerus nudus Loew, 1848 and Merodon geniculatus Strobl, 1909, from Spain, and Eumerus strigatus Walker, 1859, from California, USA. Larvae of E. nudus were obtained from swollen roots of Asphodelus cerasiferus J. Gay. Larvae of E. hungaricus were found in bulbs of Narcissus confusus Pugsley. The host plant of the examined specimen of Eumerus strigatus is unknown. Larvae of M. geniculatus were reared from bulbs of different species of Narcissus L. Scanning electron microscope imaging was used to study and illustrate the anterior respiratory processes, pupal spiracles and posterior respiratory processes of the new early stages. A compilation of all available information on the early stages and host plants of Eumerus (21 spp.) and Merodon (15 spp) is provided, as well as an identification key to all known larvae/puparia of these genera. Eumerus elavarensis Séguy, 1961 is proposed as a new synonym of E. hungaricus and first data of this species are reported from Austria, Bulgaria, Spain and Turkey. In Eumerus, larvae are alleged to rely on the previous presence of decay organisms, but in the larvae of E. nudus the sclerotisation and size of the mandibular hooks suggest that this larva can generate decay from intact plant tissue.

The genus Eumerus Meigen 1822 (Diptera: Syrphidae) is widely distributed in the Old World, though recently introduced into America, and their larvae feed on decaying vegetal material and/or inside underground storage organs of many plants, sometimes generating economic losses as pests. However, little is known about Eumerus larval cycles and their interactions with host plants.Here, immatures of three Eumerus species from different continents are described, noting their feeding habits and host plants. Larvae of Eumerus figurans Walker 1859 were obtained from Hawaiian cultured ginger roots; puparium of Eumerus alpinus Rondani 1857 originated from larvae collected in Asphodelus ramosus L. in France; puparia of Eumerus superbus Shannon 1927 were reared from larvae found in two Zamiaceae species from Australia. Mitochondrial COI sequences served for diagnosing E. figurans larvae. Optical and scanning electron microscopy were used to describe body features, head skeletons, anterior spiracles, pupal spiracles, and posterior respiratory processes. Overall, E. alpinus resembles E. nudus Loew 1848 immatures. Eumerus superbus has a remarkable morphology among all described immatures of the genus, being the only Eumerus reported from gymnosperms. Head skeleton of E. figurans suggests this species is a filtering one. Present findings show that larvae of Eumerus can be separated at the species level and that this genus is polyphagous, feeding on a wide range of plant tissues and taxa, including commercial species. This study emphasizes immature stages and breeding sites as important means to understand species life cycles and the interactions with their host plants and ecosystems.

Meromacrus is a genus of conspicuous syrphids with saprophagous larvae, ranging from the southern United States to Argentina and Chile. However, this genus is in need of a taxonomic revision. Adults reared from larvae collected in Mexico and Peru, and other material available at different institutional collections were examined. Meromacrus cactorum sp. nov., from Peru, Meromacrus yucatense sp. nov., from Mexico, their puparia and breeding sites were described. A key to Meromacrus puparia is provided. The holotypes of Meromacrus canusium, Meromacrus gloriosus, Meromacrus laconicus and Meromacrus melmoth were also examined. The name Meromacrus draco is proposed as a junior synonym of M. gloriosus. Larvae of M. cactorum sp. nov. were found in decaying columnar cacti in Peru, while those of M. yucatense sp. nov. in a rot-hole of a Ceiba pentandra stump. Obtained results on both taxonomy and biology of these species serve as a first step towards a revision of the entire genus.

Modern society has lost its natural connection with the environment. Present agriculture methods and city planning around the world support this fact. Humanity has always simplified nature in order to control it but, far from this, we have contributed to enhance current environmental issues as air and water pollution, soil fertility loss, species extinction and climate change. Therefore, it may be reasonable to change our point of view of nature. By assuming that we are an inseparable part of nature and vice versa, we may achieve a true conservation of the richness of our planet. We must synthesise nature because every living being is a part of a bigger whole.