David C Houghton

A total of 1,510 caddisfly species representing 28 families and 155 genera are reported from the 63 states and provinces of Canada and the United States of America (USA). These species have been described over a period of nearly 270 years, with the most prolific period occurring during the 1930–1940s. The families Hydroptilidae (307), Limnephilidae (255), and Hydropsychidae (159) contain the most species, whereas six families contain less than five species each. Canada and the USA host 644 and 1,487 species, respectively. The states and provinces with the greatest species richness are Tennessee (384), Virginia (383), and Alabama (378), and those with the least are Rhode Island (27), Prince Edward Island (23), and Nunavut (15). Differences in state species assemblages largely followed a geographic pattern, with a non-metric multidimensional scaling ordination suggesting six regions of caddisfly diversity corresponding to the central, far north, northeastern, northwestern, southeastern, and southwestern portions of the study area. Caddisfly species richness was highest in the southeastern region, despite being the smallest region of the six, and lowest in the far north. Species rarefaction predicted 129–181 species remain to be discovered within the two countries, while multiple linear regression modeling using common environmental variables suggested 17 states and provinces with at least 50 species remaining to be found in each.

The adult stage of Trichoptera is valuable for assessing the biotic integrity of streams; however, it is not clear which specific metric(s) have the greatest value for doing so. In this study, >500,000 adult caddisfly specimens reflecting 299 species were sampled and identified from 903 stream sites throughout the northcentral United States. Specimen data were compiled into 31 water quality metrics encompassing taxonomic richness, diversity indices, pollution tolerance, percent dominant taxa, and relative abundance of functional feeding groups. Each metric was individually tested for its ability to predict the known percentage of undisturbed habitat upstream of each sampling site using simple linear regression modeling. Most metrics were statistically significant but had R 2 values <0.30. The highest performing models were taxonomic richness at the species (R 2 = 0.40), genus (0.52), and family (0.59) levels and the Hilsenhoff Biotic Index (HBI) (0.37). The family level of taxonomic resolution produced models with a higher R 2 value than genus or species for all four of the metrics where taxonomic resolution was tested. Multiple linear regression models of all 31 metrics (R 2 = 0.65) and of combined family richness, HBI, and the ratio of shredders to filtering collectors (0.62) exhibited modest improvements over using family richness exclusively. These results indicated that simple taxonomic richness metrics constitute the most effective predictors of undisturbed upstream habitat when using adult caddisfly data, and that family richness may be the most effective of all due to low stochastic variation and ease of use.

Based on a synthesis of the literature and museum records, as well as our own ultraviolet backlight sampling during 2022-2024, we list 112 caddisfly species from Nebraska, including 61 species, 11 genera, and 4 families reported from the state for the first time. Indicative of a disturbed agricultural environment, the fauna was dominated by Hydropsychidae, Hydroptilidae, and Leptoceridae, with these 3 families accounting for 68% of species richness, 88% of species occurrence records, and 98% of total specimens collected. Previously reported species that we were not able to collect in our 2022-2024 blacklight sampling were mostly in the families Limnephilidae and Phryganeidae. Species rarefaction predicted that at least another 15-50 species remain to be found in Nebraska, probably within the less disturbed central and western portions of the state.

Based on recent collecting and a synthesis of ~100 years of historical data, 219 caddisfly species are reported from the state of Indiana. Seventeen species are reported herein from the state for the first time, including two previously thought to be endemic to the southeastern USA. Species records are also presented herein organized by drainage basin, ecoregion, glacial history, and waterbody type for two distinct time periods: before 1983 and after 2005. More species were reported from the state before 1983 than after 2005, despite collecting almost 3× the number of occurrence records during the latter period. Species occurrence records were greater for most families and functional feeding groups (FFGs) for the post-2005 time period, although the Limnephilidae, Phryganeidae, Molannidae, and Lepidostomatidae, particularly those in the shredder FFG, instead had greater records before 1983. This loss of shredders probably reflected the ongoing habitat degradation within the state. While species rarefaction predicts only a few more species to be found in Indiana, many regions still remain under-sampled and 44 species have not been collected in >40 years.

AbstractThe biotic integrity of streams is frequently compromised by anthropogenic disturbance; thus, it is important to study the potential mitigating effects of undisturbed riparian zones on streams within disturbed watersheds. In this study, two first-order northern Michigan streams located 1 km apart in adjacent agricultural watersheds, but with differing riparian land use, were compared to observe the effects of intact forest within the immediate 100 m stream corridor. Both streams had high specific conductance values associated with agricultural streams. The stream with a primarily forested riparian corridor, however, had greater canopy cover, faster stream velocity, greater coarse substrate, lower percentage of organic sediment, lower water temperatures, higher dissolved oxygen, higher taxonomic richness, higher relative biomass of shredders, lower relative biomass of gathering collectors, and more pollution intolerant taxa than the stream with a primarily agricultural corridor. Moreover, the benthic macroinvertebrate assemblages were highly distinct from each other, with the riparian forested stream dominated by aquatic insects like mayflies and caddisflies, and the agricultural stream by non-emergent isopods and amphipods. These results demonstrate the effects of a buffer zone on stream substrate composition, water physicochemistry, and benthic assemblages, and indicate the importance of preserving riparian zones within agricultural watersheds.