Long-term emergence patterns of black flies (Diptera: Simuliidae) in northwestern Pennsylvania

Spatial and temporal patterns of black fly emergence at three sites over a 7-year to 11-year period are presented. This study is the longest, continuous collection of emerging black flies ever undertaken. Because ovipositing females were able to enter emergence traps, analysis of emergence patterns for the Simulium vittatum Zetterstedt and S. tuberosum Lundström complexes, was restricted to males. Year, season and stream temperature had significant effects on mean emergence for these complexes. Sampling stations on the same system and within close proximity exhibited synchronous emergence patterns, whereas streams in close proximity but in separate basins showed asynchronous patterns. Dissimilarities might reflect divergent temperature regimes. We suggest that emergence-trap data might provide a less variable picture of community structure than larval data.     

Simuliidae (Diptera) of Sabah (British North Borneo)

This paper is based on collections made in Sabah by John Smart and on an examination of named material (types) in the British Museum (Natural History), London.
Segregates discussed comprise:(1) six new species, (2) five named species from the area, described by the late F. W. Edwards (1933).     

Insular black files (Diptera: Simuliidae) of North America: tests of colonization hypotheses

Aim To understand factors that facilitate insular colonization by black flies, we tested six hypotheses related to life‐history traits, phylogeny, symbiotes, island area, and distance from source areas. Location Four northern islands, all within 150 km of the North American mainland, were included in the study: Isle Royale, Magdalen Islands, Prince Edward Island, and Queen Charlotte Islands. Methods Immature black flies and their symbiotes were surveyed in streams on the Magdalen Islands, and the results combined with data from similar surveys on Isle Royale, Prince Edward Island, and the Queen Charlotte Islands. Black flies were analysed chromosomally to ensure that all sibling species were revealed. Tests of independence were used to examine the frequency of life‐history traits and generic representation of black flies on islands vs. source areas. Results A total of 13–20 species was found on each of the islands, but no species was unique to any of the islands. The simuliid faunas of the islands reflected the composition of their source areas in aspects of voltinism (univoltine vs. multivoltine), blood feeding (ornithophily vs. mammalophily), and phylogeny (genus Simulium vs. other genera). Five symbiotic species were found on the most distant island group, the Magdalen Islands, supporting the hypothesis that obligate symbiotes are effectively transported to near‐mainland islands. An inverse relationship existed between the number of species per island and distance from the source. The Queen Charlotte Islands did not conform to the species–area relationship. Main conclusions The lack of precinctive insular species and an absence of life‐history and phylogenetic characteristics related to the presence of black flies on these islands argue for gene flow and dispersal capabilities of black flies over open waters, possibly aided by winds. However, the high frequency of precinctive species on islands 500 km or more from the nearest mainland indicates that at some distance beyond 100 km, open water provides a significant barrier to colonization and gene exchange. An inverse relationship between number of species and distance from the source suggests that as long as suitable habitat is present, distance plays an important role in colonization. Failure of the Queen Charlotte Islands to conform to an area–richness trend suggests that not all resident species have been found.     

The aquatic drift patterns of black flies (Diptera: Simuliidae)

Larval (5th-final instar) drift patterns of five species of black flies (Prosimulium mixtum, Stegopterna mutata, Simulium tuberosum FG, S. vittatum IIIL-1, and S. vittatum IS-7) were analyzed. The diel drift patterns were not species-specific, but consistently exhibited a marked increase after sunset, preceded by a period of minimal drift. The drift minimum generally occurred during or shortly after the period of maximum water temperature. Larvae showed significantly more nocturnal than diurnal drift. Pupal drift was attributed to accidental detachment from the substrate. Adult drift was over 90% diurnal and usually composed primarily of teneral individuals. Upstream larval movements of the S. vittatum and S. tuberosum complexes were each less than 6.5% of the total upstream and downstream larval movements. The proportion of parasitized larvae of the S. vittatum and S. tuberosum complexes was generally higher in the benthos than in the drift. Based in part on data included in a thesis submitted by the senior author to The Pennsylvania State University in partial fulfillment of the requirements for the Ph. D. degree.     

Distribution patterns of blackfly (Diptera: Simuliidae) associations in two Irish river systems

Nine blackfly species were found in two river systems in south western Ireland. Their distribution patterns reflected the three main types of running waters: head waters and mountain brooks; meadow streams and river sections at lower altitudes; lake outlets. Cluster analyses showed correlations between the five most dominant blackfly species and stream sites, as well as with some environmental factors. Larval gut analyses demonstrated that in general the supply of suspended algae determined larval gut content, but there were distinct differences in food utilization between associated larvae.     

Diversity, distribution and larval habitats of North Swedish blackflies (Diptera: Simuliidae)

1. Blackfly species richness and community structure were analysed at fifty-six sites in northern Sweden in two seasons. The sites were situated in a wide range of streams and rivers from small springbrooks, bog streams and lake-outlet streams to medium-sized forest rivers and large rivers draining montane regions.
2. Thirty-nine blackfly species were found, with between two and thirteen species per site. Neither species richness nor abundance could be related to the environmental variables measured.
3. An analysis of labral fan size of blackflies indicated a clear trend for the prevalence of larvae with small fans in large rivers and larvae with larger fan size in small streams. Similarly, fan size related to current velocities so that large fans were associated with slow current velocities and small fans with high velocities.
4. A strong relationship existed between species composition and habitat, as seen in ordination by non-metric multidimensional scaling. The relationship found between fan size and habitat size-related variables, such as channel width, depth, velocity and substratum particle size, along with longitude and altitude, in partial least squares regression analysis offered an explanation of the species composition–habitat relationship.
5. In addition to testing that distributions of blackfly larvae reflect morphological traits, we tested two general hypotheses pertaining to distribution patterns: (a) that blackfly communities show bimodal distributions; and (b) that their distributions are nested. Neither of these two hypotheses was supported by our observations. However, widespread blackfly species were locally more abundant than those found at relatively few sites, thus showing a positive abundance–occupancy relationship.     

Five Simuliidae (Diptera) from West Cameroon

The male, female, pupa and larva of a new phoretic species of Simulium are described. A new species-group is established for this species and S.diceros, and its systematic position is discussed. Two other new species of Simulium are described from pupal material, and new forms of S.palmeri and S.berghei are recorded.     

A cytogenetic analysis of the Simulium ochraceum species complex (Diptera: Simuliidae) in Central America.

A cytobiotaxonomic study of the medically important insect vector Simulium ochraceum s.l. revealed two sibling species and one cytotype from various endemic and nonendemic zones of human onchocerciasis in Guatemala and Mexico. Polytene chromosome maps and idiograms as well as notes on the biology of the three taxa designated S. ochraceum A, S. ochraceum B, and S. ochraceum C within the subgenus Psilopelmia are presented. All three taxa exhibit distinct sex chromosomes and taxon-specific suites of autosomal inversion polymorphisms. Simulium ochraceum C differs from both S. ochraceum A and S. ochraceum B by five interspecific inversions designated IIS-7,8 and IIIL-12, 13 + 14, 15. The three taxa exhibit niche and biting preferences, with S. ochraceum A being highly anthropophilic. Analysis of autosomal inversion polymorphism profiles indicates S. ochraceum A has long-range dispersal capability. Our results are consistent with the general findings that in the Simuliidae, sibling speciation may be suspected wherever a morphospecies occupies different niches in a stream continuum. We find for the first time an apparent partitioning of taxa by altitude. Simulium ochraceum A may be a primary vector of human onchocerciasis in Guatemala, as its vertical distribution is coincident with that of the highest areas of nodule prevalence in the human population. A genotypic component of variation in vectorial capacity of S. ochraceum A populations seems to occur, since the Y4 chromosome and its X chromosome counterpart are associated with hyperendemic areas of human onchocerciasis. Our observation that a supernumerary band, 37B1Hb, is associated with sex determination in two of the taxa may be of significance for the elucidation of the molecular basis of sex determination and possible resolution of issues pertinent to the general model of sympatric speciation in the Simuliidae.     

Patterns of mtDNA diversity in northwestern North America

The mitochondrial DNA (mtDNA) haplogroups of 54 full-blooded modern and 64 ancient Native Americans from northwestern North America were determined. The control regions of 10 modern and 30 ancient individuals were sequenced and compared. Within the Northwest, the frequency distribution for haplogroup A is geographically structured, with haplogroup A decreasing with distance from the Pacific Coast. The haplogroup A distribution suggests that a prehistoric population intrusion from the subarctic and coastal region occurred on the Columbia Plateau in prehistoric times. Overall, the mtDNA pattern in the Northwest suggests significant amounts of gene flow among Northwest Coast, Columbia Plateau, and Great Basin populations.     

Durability of Simuliid Silk Pads (Simuliidae,Diptera)

A central aspect of simuliid adaption to life in moving water is a silky secretion which they produce in their salivary glands. This secretion is spread on the substrate surface thereby enabling adhesion of the posterior abdominal hooks of the larvae to the substrate surface. Therefore, silk pads are a prerequisit for simuliid filter‐feeding as well as any kind of locomotive activity. If silk pad adhesion is weak, larvae risk drifting off, either directly or during locomotion. Properties of the adhesive (=silk) as well as the substrate surface may cause weak adhesion. A specialist such as S. noelleri which has little chance of surviving after drifting off its lake outlet habitat, should have adaptations to reduce this risk. Such an adaptation could be very durable silk pads, giving larvae the chance to be safely attached for a relatively long time. In this study larval silk pads of S. ornatum and S. noelleri were stained using Giemsa's staining procedures. Changes in silk pad structure and traces of rot after 2–33 days of exposure to stream water were recorded and compared. Silk pads of S. ornatum and S. noelleri showed differences which indicate differences in ageing processes and biochemistry of this secretion.     

Checklist of the family Simuliidae (Diptera) of Finland

A checklist of the family Simuliidae (Diptera) is provided for Finland and recognizes 56 species. One new record has been added (Simulium latipes) and one name sunken in synonymy (Simulium carpathicum). Furthermore, Simulium tsheburovae is treated as a doubtful record.     

Molecular phylogeny of the North American Simulium malyschevi‐group species (Diptera: Simuliidae)

We investigated species limits and phylogenetic relationships among chromosomally distinct North American members of the Simulium malyschevi species‐group. Maximum parsimony and Bayesian analyses were conducted based on 12S, COII, cyt b and ITS‐1 gene sequences. In terms of species limits, monophyly was highly supported for each chromosomally and morphologically distinct taxon analysed (S. decimatum, S. defoliarti, S. malyschevi, and S. murmanum). In contrast, support for monophyly of morphologically homogeneous S. arcticum complex members was significant only in one case (S. saxosum) and not the other (S. negativum). Considering the overall topology, three principal conclusions were drawn: (i) the status of S. subvariegatum as a member of the S. malyschevi species‐group remains uncertain. This species either was excluded from the malyschevi‐group or formed a sister group with S. malyschevi at the base of the tree; (ii) although S. murmanum and S. decimatum branch after S. malyschevi, the position of the two species relative to each other remains unresolved; and (iii) the structurally homogeneous S. arcticum species complex was not monophyletic due to the inclusion of S. defoliarti. Further investigation may warrant changes to current malyschevi‐group classification. Molecular datasets alone may be insufficient for resolving relationships among particular lineages of black flies.     

On the distribution of Temnostoma vespiforme (Diptera, Syrphidae) in North America

The occurrence of Temnostoma vespiforme (L.) in the Holarctic Region is questioned. The North American specimens previously determined as T. vespiforme (L.) are re-examined. Their differences from the European specimens in the body coloration and in the morphology of the male and female genitalia are listed.     

Flow patterns around cocoons and pupae of black flies of the genusSimulium (Diptera : Simuliidae)

Flow patterns around structurally different cocoons and pupae of five species ofSimulium Latreille are described. Three features of the flow pattern common to all cocoons are; 1) a solenoidal vortex around the cocoon, 2) upward flow anterior (downstream) to the cocoon, and 3) one or two pairs of spiral-shaped vortices, which either touch or envelop the fill filaments of the pupa. The solenoidal vortex and the upward-spiralling, downstream vortices are common features of flow patterns around most bluff bodies submerged in a boundary layer. The proximity of the vortices to the fill filaments of all pupae suggests that these vortices are associated with gaseous exchange at the gill filaments.     

Six new species of Acomoptera from North America (Diptera, Mycetophilidae)

Six new species are described, raising the number of North American Acomoptera species to seven and the genus total to ten, and nearly doubling the number of species within the putative clade containing Acomoptera, Drepanocercus, and Paratinia. These novel species forms have implications for the concept of Acomoptera that in turn, may impact our understanding of its generic relationships and the evolution and composition of Gnoristinae and Sciophilinae. The new species, Acomoptera crispa, Acomoptera digitata, Acomoptera echinosa, Acomoptera forculata, Acomoptera nelsoni,and Acomoptera vockerothi, are compared with the type species of the genus, Acomoptera plexipus (Garrett), whose diagnostic features are imaged and illustrated for the first time. The European species, Acomoptera difficilis (Dziedzicki) is also illustrated and compared. Acomoptera spinistyla (Søli) comb. n. is transferred from Drepanocercus. A key to species is provided. Future work will seek to incorporate this knowledge into a systematic phylogenetic study of relationships between these species and their sister taxa.     

Polytene chromosomes of Simulium craigi (Diptera: Simuliidae)

Simulium craigi Adler and Currie is a polymorphic species based on polytene chromosome banding patterns in the long arm of chromosome III (IIIL). Three cytotypes are described based on the predominant IIIL sequences. These correspond to three broad geographic areas: cytotype CC from Pennsylvania; cytotype AF from Ontario and Manitoba; and cytotype ACF/BCF from New Hampshire. In the absence of sympatric populations, these cytotype differences are best explained by clinal variation within a single species. The relationship of S. craigi to other described members of the S. vernum group is discussed.     

Ecology and speciation in African Blackflies (Diptera:Simuliidae)

The simuliid fauna of the Ethiopian region is notably isolated, only two of its species occurring elsewhere; the region has 124 described species, and others still undescribed. Simuliid larvae and pupae are adapted to attachment in moving water; adult females may disperse over considerable distances. This paper considers three examples of evident speciation in an ecological context:(1) speciation on afromontane 'islands' (2) the Simulium naevei group and the adaptive significance of the association between the early stages and freshwater crabs; (3) the S. damnosum complex, which includes the widespread vectors of human onchocerciasis. Maps show the distribution of species in these three groups.