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The eastern Nearctic fauna of Blepharicera Macquart (Diptera: Blephariceridae) is revised to include 23 species, six of which are new to science. Descriptions of the larvae, pupae and adults of B. amniculasp.n., B. coniferasp.n., B. cristasp.n., B. enoristerasp.n., B. hillabeesp.n. and B. opisterasp.n. are presented. Keys to instar IV larvae, pupae and adults of all eastern Blepharicera, except B. caudata for which pupae and adults remain unknown, are provided. Phylogenetic studies were conducted to determine the relationships between eastern and western Nearctic Blepharicera and among species within these groups. Morphological data for 44 characters were used to test previous phylogenetic hypotheses on the historical relationships and biogeography of Nearctic Blepharicera. Maximum parsimony analyses support monophyly of the B. tenuipes and B. micheneri groups.

Based partly on recent collections from Nepal and northern Thailand, new data are added to the knowledge of Horaia Tonnoir. Pupal and larval stages of H. montana Tonnoir are re-described, larval descriptions for H. manaliella (Kaul) are provided, and two new species, H. diminutiva and H. namtoki, and a new subspecies, H. montana piedmonti, are described. Dichotomous keys to adults, pupae and instar IV larvae of blepharicerid genera from south-east Asia and of all known species of the genus Horaia are provided. Phylogenetic analysis of the tribe Apistomyiini suggests that Horaia is a monophyletic genus closely related to a clade containing Apistomyia Bigot and Parapistomyia Zwick. This clade is, in turn, sister to a weakly supported clade comprising Theischingeria Zwick +Austrocurupira Dumbleton. The New Zealand endemics Peritheates Lamb +Neocurupira Lamb are proposed as sister group to other apistomyiines, within which Nothohoraia Craig + (Curupirina Stuckenberg +Nesocurupira Stuckenberg) is sister group to the remaining genera. The proposed phylogeny supports Zwick’s Antarctic origin hypothesis for the biogeography of the Apistomyiini in Asia and Australasia.

SUMMARY 1. Monthly patterns of diatom ingestion by Blepharicera magna and B. similans (Diptera: Blephariceridae) larvae were examined to determine whether dietary attributes fluctuate within the final-instar stadium. The two species are isolated temporally: B. magna diets were examined from October to December, and B. similans diets were examined from June to August. Each month, the diatom assemblage of larval diets was assessed and compared with that of the forage base. In addition, total diatom ingestion was estimated. 2. Larval gut samples were ordinated on the basis of relative abundance of common diatom taxa, and month‐month comparisons of larval diets were made, which revealed that (i) B. magna dietary assemblages did not vary significantly from October to December; (ii) diatom species composition of B. magna diets generally resembled that of the forage base; and (iii) B. similans dietary assemblages varied significantly from June to August, with few changes attributable to seasonality of ambient diatom flora. 3. Total diatom ingestion by B. magna was relatively stable from October to December. For B. similans, total diatom ingestion was greatest in July, when larvae were midstage of instar IV. The latter result was accompanied by increased ingestion of grazer-resistant diatom taxa (e.g. Achnanthes deflexa var. alpestris, Achnanthidium minutissimum, and Cocconeis placentula var. lineata), which can be more digestible than grazer-susceptible taxa (e.g. chain-forming Fragilaria and rosette-forming Synedra species). This result suggests demand for a large quantity of nutritionally rich food at midstage of instar IV, which could represent a period of critical growth for B. similans.

SUMMARY 1. Fourteen populations of Liponeura cinerascens minor from different sites in the Swiss Alps were investigated. Our goals were to describe the life history of this blepharicerid species and to analyse how it was influenced by temperature and food availability. 2. Temperature regimes and periphyton density at the sampling sites varied considerably. Mean annual temperature ranged from 3.8 to 6.5 °C, with annual amplitudes (i.e. the difference between the mean of the coldest and the warmest month) between 3.7 and 12.0 °C. Averaged periphyton density, which was assessed semiquantitatively on a scale from 0 to 5, ranged from 1.1 to 3.3. 3. Larvae or pupae of L. c. minor were found between January and October. Presence of larvae or pupae at individual sites ranged from 100 to 224 days and appeared to be mainly a result of hatching patterns. Individual larval development required between 7 and 20 weeks. Our findings suggest that L. c. minor is univoltine and undergoes an extended (≥4 months) egg dormancy during late summer, autumn and winter. 4. Development of L. c. minor was observed from 800 degree-days where periphyton availability was low. 6. No evidence for intraspecific food competition was found, whereas food competition by other blepharicerid species, mainly Hapalothrix lugubris, appeared to be a major reason for the observed food limitation. However, as L. c. minor is much more widespread than H. lugubris, food competition between these two species is likely to occur infrequently. We therefore contend that variations in the life history of L. c. minor are mainly a consequence of its thermal constraints.

1. Larval net-winged midges (Diptera: Blephariceridae) possess six ventral suckers that enable them to inhabit swift streams. Each sucker consists of a suction disc and a cavity with a piston. Large muscles are inserted within the piston, as well as at the base of the suction disc. This structure infers that both attachment and release of the sucker is achieved by vertical movements of the piston. 2. Live observations of blepharicerid larvae revealed that the sucker is indeed attached by an upward movement of the piston, but that the cavity is flooded when the sucker is released. The piston is lowered only at the end of a sucker ‘step’, expelling water from the cavity. 3. During foraging, the maxilla and the piston of the first sucker are moved synchronously, indicating that the first sucker functions as a holdfast thus facilitating grazing. 4. The adhesive forces, as well as the relative size of blepharicerid suckers, differ amongst species. They are highest in Hapalothrix lugubris and lowest in Liponeura cordata, which correlates with the hydraulic stress to which the larvae of these species are exposed in their preferred habitat. The balance between the efficiency of their retention structure and the hydraulic conditions of their preferred habitat defines a key dimension of their ecological niche.

1. The net-winged midges (Diptera: Blephariceridae) are a highly specialized group whose morphological characteristics and specific habitat requirements suggest a limited potential for dispersal. Levels of genetic variation were examined within streams, between streams in the same range and between mountain ranges in larval populations of Elporia barnardi in the south-western Cape of South Africa. The aim was to examine the hypothesis that population structure would reflect the poor potential for dispersal. 2. Significant deviations from Hardy–Weinberg equilibrium in 17 of the 57 individual comparisons indicate a non-random mating population. Given the swarming behaviour and life history traits, larvae sampled may reflect the product of limited matings. 3. Analysis of population substructuring revealed significant levels of differentiation among geographically proximate populations. Large differences between streams within Table Mountain, similar in magnitude to those between mountain ranges, suggest that movement of individuals out of the stream catchment is rare. Observed FST values are more similar to those of fully aquatic species than other lotic insects with winged adult stages. 4. Results suggest that mountain ridges provided effective physical barriers to the dispersal of E. barnardi, with the catchment representing the effective population unit.

A taxonomic treatment of the Australian net-winged midges (Diptera: Blephariceridae) of the tribe Apistomyiini is presented. Characters supporting the monophyly of the tribe are described and illustrated. New taxa are Theischingeria rieki gen. et sp. nov., Parapistomyia mueller sp. nov. and Parapistomyia bulbifera barringtoniana ssp. nov., bringing the total number of Australian Apistomyiini to eight species and subspecies in four genera. the New Guinean Curupirina papuana Zwick and Hortle is transferred to the Australian genus Parapistomyia Zwick; its adult and pupa are described. A morphocline between the two Australian species of Apistomyia is described. New keys to larvae, pupae and adults of all Australian Apistomyiini are presented. the phylogenetic relationships within the tribe are discussed.

A cladistic analysis of the Blephariceromorpha (here including the Nymphomyiidae, Deuterophlebiidae and Blephariceridae) and related Diptera provides a test of the phylogenetic hypotheses of Rohdendorf (1964, 1974), Hennig (1973), Wood & Borkent (1989) and Courtney (1990a). In particular, monophyly of the Blephariceroidea and Blephariceromorpha (sensu Wood & Borkent), and their relationship to other Diptera, is tested. Evaluation of larval, pupal and adult characters supports the hypothesis of Wood & Borkent, as modified by Courtney. Four larval features suggest that the Blephariceromorpha + Psychodomorpha form a monophyletic group, although an alternate hypothesis predicting that the Blephariceromorpha is the sister group of the Psychodomorpha + (Ptychopteromorpha + Culicomorpha), is discussed. Monophyly of the Blephariceromorpha (Nymphomyioidea + Blephariceroidea) is supported by one adult and five larval characters. Monophyly of the Blephariceroidea (Deuterophlebiidae + Blephariceridae) is supported by thirteen synapotypies, including features of the larva (six), pupa (three) and adult (four). Nineteen, nineteen and nine hypothesized synapotypies support monophyly of the Nymphomyiidae, Deuterophlebiidae and Blephariceridae, respectively.

We assessed effects of the experimental insecticide Zectran(R) on aquatic organisms in Bear Valley Creek, Idaho in 1966. Hayden Creek drainage, nearby and not sprayed, served as a control. We found no significant fish mortality, and no effect on growth rate and condition of age 0+, 1+, 2+, and 3+ dolly varden (Salvelinus malma). Insecticide applications did not increase emigration and intrastream movement of fish. We noted no effects on benthic aquatic insect numbers, but observed that more insects drifted downstream for several hours beginning about 3 hours after spraying on 7 July 1966. Adult terrestrial insects, immature Heptageneidae and Rhyacophilidae, adult Chloroperlidae, and immature and adult Phryganeidae, Limnephilidae, and Blephariceridae increased in drift samples after spraying. We concluded that Zectran insecticide damaged aquatic organisms very little.