Drastic acceleration of the extinction rate of hoverflies (Diptera: Syrphidae) in the Netherlands in recent decades, contrary to wild bees (Hymenoptera: Anthophila)

The averaged yearly rate of extinction of hoverfly species (Diptera: Syrphidae) in the Netherlands is shown to be variable over time: over the period 1993–2017, it is nearly five times higher than over the period 1942–1992. There is a sharp demarcation between the two rates at 1992–1993. This sudden change in extinction rates is due to an accelerated extinction rate of species with zoophagous and phytophagous larvae. In species with aquatic saprophagous larvae or saproxylic larvae no rate change is observed. In contrast to hoverflies, extinction rates for bees in the Netherlands are found to be constant over time, higher than hoverflies in the first period, but lower than hoverflies in the last period. Current extinction speeds are 1.0 species a year for hoverflies (= 0.3 % of all species present per year) and 0.4 species a year for bees (= 0.12 % of all species present per year). These results differ in a major way from previous results. Consequently, from the point of view of conservation, hoverflies deserve a more prominent role in conservation policy making.