Disproportionate declines of formerly abundant species underlie insect loss.

Studies have reported widespread declines in terrestrial insect abundances in recent years, but trends in other biodiversity metrics are less clear-cut. Here we examined long-term trends in 923 terrestrial insect assemblages monitored in 106 studies, and found concomitant declines in abundance and species richness. For studies that were resolved to species level (551 sites in 57 studies), we observed a decline in the number of initially abundant species through time, but not in the number of very rare species.

InsectChange: a global database of temporal changes in insect and arachnid assemblages.

Insects are the most ubiquitous and diverse group of eukaryotic organisms on Earth, forming a crucial link in terrestrial and freshwater food webs. They have recently become the subject of headlines because of observations of dramatic declines in some places. Although there are hundreds of long-term insect monitoring programs, a global database for long-term data on insect assemblages has so far remained unavailable.

Complex Messages in Long-Term Monitoring of Regal Fritillary (Speyeria idalia) (Lepidoptera: Nymphalidae) in the State of Wisconsin, USA, 1988-2015.

The regal fritillary ("regal") () is endangered in Wisconsin, USA, and declining and at risk range-wide. During 1988-2015, we surveyed 24 known regal sites and >100 areas of potential habitat in Wisconsin. We recorded 9037 individuals in 742.

Status and Trend of Regal Fritillary (Speyeria idalia) (Lepidoptera: Nymphalidae) in the 4th of July Butterfly Count Program in 1977-2014.

Regal Fritillary (Speyeria idalia) primarily inhabits prairie, a native grassland of central North America, and occurs rarely in nonprairie grasslands further east. This butterfly has experienced widespread decline and marked range contraction. We analyze Regal Fritillary incidence and abundance during 1977-2014 in 4th of July Butterfly Counts, an annual census of butterflies in North America.

Twenty Years of Elfin Enumeration: Abundance Patterns of Five Species of Callophrys (Lycaenidae) in Central Wisconsin, USA.

We recorded five species of elfins (Callophrys) during annual spring surveys targeting frosted elfin C. irus (state-listed as threatened) in 19 pine-oak barrens in central Wisconsin USA during 1994-2013. At the northwest end of its range here, C.

Decline of Hesperia ottoe (Lepidoptera: Hesperiidae) in Northern Tallgrass Prairie Preserves.

We counted butterflies on transect surveys during Hesperia ottoe flight period in 1988-2011 at tallgrass prairie preserves in four states (Illinois, Iowa, Minnesota, Wisconsin), divided into units cross-referenced to vegetation type and management history. H. ottoe occurred only in dry and sand prairie types, and was significantly more abundant in undegraded than semi-degraded prairie, and in discontinuous sod (with numerous unvegetated areas due to bare sand and/or rock outcrops) than in continuous sod.