Evaluation of Bacillus thuringiensis as a biocide of blackfly larvae (Diptera: Simuliidae)

Thirteen strains of Bacillus thuringiensis were bioassayed against late-instar larvae of field-collected Simulium vittatum. All 13 strains caused significant blackfly mortality. The mortalities ranged from 64% for the HD 225 strain to 88% for HD 39 at 10 ppm for a 24-hr exposure period. A minimum 24 hr of exposure to a minimum concentration of 10 ppm was required to produce mortalities approximating 90%. The LC₅₀ values for the HD 39 and HD 225 strains were 1.1 and 1.0 ppm, respectively.     

Unsuitability of introduced tiles for sampling blackfly larvae (Diptera: Simuliidae)*

SUMMARY. 1. Blackfly larvae were collected from twenty-one stations in five lake outlets in Southern Quebec. Tiles (total area=500cm²) were introduced in early March, and collected 4 weeks later: randomly selected rocks (30–500cm) from the surrounding area were collected at the same time. 2. Larval densities on tiles were significantly less variable than on rocks. The variance of density estimates on tiles averaged 36% of the observed variance on natural rocks, or 67% when variance on rocks was corrected for average rock size. 3. Tiles significantly overestimated densities on rocks in some streams, and significantly underestimated them in others. These differences could not be explained by microhabitat differences (distance from the lake, depth, current velocity) between rock and tile samples. The bias that tiles introduce in density estimates precludes their use in comparisons among sites.     

Contribution to the blackfly fauna (Diptera: Simuliidae) of Iran

A collection of blackflies (Diptera: Simuliidae) from western Iran was examined, four species were recorded. Three new species are described: Tetisimulium iranicum sp. n., Wilhelmia lurestanica sp. n., and Crosskeyellum zagros sp. n. The presence of Tetisimulium coarctatum (Rubzov, 1940) in Iran is confirmed.     

Feeding by blackfly larvae (Diptera: Simuliidae) forming dense aggregations at lake outlets

1. Larvae of Simulium noelleri formed dense aggregations (>60 larvae cm^?2) at a lake outlet where water passed in a very thin film vertically over wooden planks. Despite the high densities there was sufficient space between larvae to allow water to flow within an aggregation as well as over its surface. 2. Small larvae, occluded within an aggregation, had a faster midgut throughput rate than larger larvae. Both had rates that were similar to those recorded in the literature for a range of habitats and species. The same relationship of throughput rate and larval size was maintained from upstream to downstream across 20cm of an aggregation. 3. Material passed through the midgut of larvae of a given size at a constant rate, indicating that assimilation efficiency of the whole gut contents was low. 4. By colour-banding larval gut contents with fluorescent dye it was possible to demonstrate that faecal pellets are a component of the larval diet in the dense aggregations, especially of small larvae. 5. The abundance of four easily identifiable components of the lake seston were measured from water samples above, and below, a larval aggregation. Particles with a mean diameter of 40 μm, or greater, showed significant reductions in numbers over a stream length of 6cm. Particles of smaller size showed reductions but these were not significant.     

Size selection of latex beads by blackfly larvae (Diptera: Simuliidae) in the laboratory

In laboratory experiments, blackfly larvae collected from a lake outlet, a woodland and a meadow stream were tested for size selection of latex beads of < Ito > 100 μm diameters. 3 suspensions of varying proportions for each size category were supplied to these blackfly larvae in common experiments. Comparisons between the size frequency distributions of particles supplied and the particle compositions in the larval guts showed intra- and interspecific differences and were quantified by calculating Jacobs' electivity index. In all species selection of larger particles increased with the larger larval instars. Although there was a positive selectivity of small particles in some cases, the ingested proportion of large particles increases volumes and biomasses of gut content and may be more important for larval growth than small particles.     

Growth,respiration, and assimilation of blackfly larvae (Diptera: Simuliidae) in a lake-outlet in Finland

Summary A field experiment on feeding-rate in blackfly larvae (Diptera: Simuliidae) was conducted in the River Teuronjoki near its origin from Lake Pääjärvi, Finland. Small larvae were seen to feed more rapidly than large larvae.The increase in mean body-tissue weight of the larvae in Teuronjoki was determined and, from this relationship, growth-rate day^-1 for the larvae was obtained.In the laboratory, respiration-rate was determined for larvae of known body-tissue weight. Experiments were conducted when animals were feeding to replicate, as closely as possible, the conditions in the field. Respiration costs were higher for small, than for large, larvae.Estimates of assimilation-rate could be obtained by addition of growthrate and respiration-rate for larvae of given body-tissue weight. As the weight of material ingested per unit of time was known it was therefore possible to calculate assimilation efficiency. The values given in this study are the lowest yet recorded for freshwater detritivores.The study was conducted at Lammi Biological Station, University of Helsinki, Finland     

Relationships between labral fan morphplogy, body size and habitat in North Swedish blackfly larvae (Diptera: Simuliidae)

A comparison was made of the labral fan morphology of 29 populations belonging to at least 21 different simuliid species present as mature larvae in spring-early summer in North Swedish streams and rivers. The study revealed that there are both adaptive, morphological and phylogenetic traits evident in the material. Two basically different particle capture techniques can be deduced from morphology, where two prosimuliids, Cnephia pallipes and Metacnephia trigonia , represent species which mainly rely on a sieving technique, whereas all other species investigated capture particles by some other process, such as diffusional deposition. Within tribe Simuliini there are significant relationships between several fan traits and habitat. Thus, fast rivers are inhabited by species with small fans, having short and stout rays, whereas small, slow streams harbour species with large fans consisting of elongated, delicate rays. The finer morphology of the fan rays in terms of secondary structures, the microtrichia, appears to be more related to phylogeny than" habitat. Since a phylogeny of blackfly species still is lacking, this conclusion cannot be tested. In two subgenera, however, which are particularly well represented in the present material ( Simulium s. str. and Nevermannia ), and whose taxonomy is based on criteria other than fan morphology, there is consistent support for the conclusions about habitat-morphology relations.     

Factors influencing nuisance blackfly (Diptera: Simuliidae) activity in the Scottish Highlands

Abstract. The nuisance activity of blackflies (Diptera: Simuliidae) was investigated in several habitats on Speyside, near Kincraig (57^o08'N, 3^o56'W), Invernesshire, in central Scotland during May-October 1987-89.
The main blackfly species caught landing/biting on humans were Simulium reptans, S. argyreatum, S. variegetum and the S. tuberosum complex, in order of prevalence. Blackfly biting activity occurred from mid-May to mid-September. Numbers of female blackflies attracted to volunteers were correlated with their body posture, habitat and the season. Overall, Simulium activity was greatest in mixed birch/juniper forest, least in spruce plantations and at intermediate levels on pasture, moorland and in Scots Pine forest.
Compared with an adult, a child experienced twice as many Simulium bites per hour (12.2 v 6.3) in the birch forest. On the child's body, 69% of blackfiies landed on the head, neck and back, whereas the majority landed on the legs (48%) and arms (28%) of adults. Bending over, especially during the exertion of gardening, was more attractive to anthropophilic blackfiies than standing or kneeling.     

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.     

Cytogenetic features of the blood-sucking blackfly Wilhelmia paraequina Puri (Diptera: Simuliidae) from Armenia

Three blackfly Wilhelmia paraequina populations of Armenia (rivers Debet and Megriget, channel Megri) were studied. 2n = 6: IS + IIL, IIS + IL, IIIS + IIIL. Cytological maps of polytene chromosomes were constructed. High inversion polymorphism (95.63%) was observed, with 2.6 inversions per individual. Three inversions proved to be associated with male development: Y1 was characterized by a combination of two heterozygous inversions, IIL-3 + IIL-1, while Y2 had another combination of heterozygous inversions, IIL-5 + IIL-3. The X chromosome had a standard homozygous IIL disk sequence. The populations were shown to be similar in autosomal polymorphism. A tendency for differentiation was observed with respect to frequencies and types of sex-linked inversions: the sex determination system was Y1X-XX in the Debet and Megriget populations and Y2X-XX in the channel (Megri) population. On the strength of these findings, one W. paraequina morphotype was assumed to involve two cytotypes, A (Debet and Megriget populations) and B (Megri population).     

贵州蚋属一新种 (双翅目：蚋科)

 记述采自贵州雷公山的蚋属一新种, 显著蚋Simulium (Simulium) prominentum, 新种 。根据其蛹和幼虫的特征显著而命名, 对其幼期形态进行描述并与其近缘种作分类讨论。     

贵州蚋属一新种(双翅目：蚋科)

记述采自贵州雷公山的蚋属一新种, 显著蚋Simulium (Simulium) prominentum, 新种。根据其蛹和幼虫的特征显著而命名, 对其幼期形态进行描述并与其近缘种作分类讨论。     

Contrasting responses of black fly species (Diptera: Simuliidae) to experimental whole-stream warming

1. As global temperatures continue to rise, assessment of how species within ecological communities respond to shifts in temperature has become increasingly important. However, such assessments require detailed long-term observations or ecosystem-level manipulations that allow for interactions among species and the potential for species dispersal and exchange with the regional species pool.
2. We examined the effects of experimental whole-stream warming on a larval black fly assemblage in southwest Iceland. We used a paired-catchment design, in which we studied the warmed stream and a nearby reference stream for 1 year prior to warming and 2 years during warming and estimated population abundance, biomass, secondary production, and growth rates for larvae of three black fly species.
3. Experimental warming by 3.8°C had contrasting effects on the three black fly species in the assemblage. The abundance, biomass, growth, and production of Prosimulium ursinum decreased in the experimental stream during the warming manipulation. Despite increasing in the reference stream, the abundance, biomass, and production of another species, Simulium vernum, decreased in the experimental stream during warming.
4. In contrast, warming had an overall positive effect on Simulium vittatum. While warming had little effect on the growth of overwintering cohorts of S. vittatum, warming led to an additional cohort during the summer months and increased its abundance, biomass, and production. Overall, family-level production was enhanced by warming, despite variation in species-level responses.
5. Our study illustrates that the effects of climate warming are likely to differ even among closely related species. Moreover, our study highlights the need for further investigation into the uneven effects of warming on individual species and how those variable effects influence food web dynamics and ecosystem function.

     

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 Palearctic blackfly Simulium equinum (Diptera: Simuliidae) as a biting pest of captive nyala antelopes (Tragelaphus angasii)

Blackflies (Diptera: Simuliidae) are cosmopolitan nuisance pests of great economic importance as well as vectors of many pathogens. After reports of massive blackfly biting of captive nyala antelopes in the Vienna Zoo, Austria, this study aimed to identify the species causing multiple skin lesions on the antelope hosts. The Palearctic species Simulium equinum, belonging to the medically and veterinary important Wilhelmia subgenus, was identified as the most likely causative agent. Barcoding and maximum likelihood analysis supported morphological species identification and highlighted the complex phylogeny of the subgenus Wilhelmia. Our study gives first evidence of the multi-host feeding blackfly S. equinum in the Vienna Zoo, thereby raising the question whether other hosts could also be bitten on a regular basis. The preliminary results urge for further analysis of blackfly breeding sites as well as the clarification of the host spectrum to assess the medical and veterinary importance of blackflies in the Zoo.     

Oviposition habits of a univoltine blackfly, Prosimulium kiotoense (Diptera: Simuliidae), in Kyushu, Japan

Oviposition habits of a univoltine mammalophilic blackfly, Prosimulium kiotoense Shiraki, were investigated at a stream in Kyushu Island, Japan. The flies oviposited on bryophyte mosses growing on river bank rock surfaces. The eggs were laid singly, but large irregular egg masses were often formed because many females oviposited within the same small areas. Wet sites with dense bryophyte cover at heights between 0 and 15 cm above water level were selected for oviposition. Oviposition activity was observed in the latter half of April. P. kioteonse females came to the site to lay eggs after 11.00 hours in the morning, when air temperature rose to about 15 degrees C. Peak ovipositional activity occurred between 12.00 and 14.00 hours.     

Identification of entomopathogenic Bacillus isolated from Simulium (Diptera, Simuliidae) larvae and adults.

Entomopathogenic bacteria isolated from Simulium larvae and adults from breeding sites in the states of S?o Paulo and Rio de Janeiro, Brazil, were identified as 18 strains of Bacillus thuringiensis and one of B. sphaericus. Most of these strains were serotyped according to their flagellar antigens. However, nine of the B. thuringiensis samples, could not be serotyped and were designated as "autoagglutinating"; they were also shown to be toxic in preliminary tests against Aedes aegypti larvae. Additionally, B. sphaericus was also shown to be toxic towards Culex quinquefasciatus larvae.