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PubMed2006

Feeding behavior of larval black flies (Diptera: Simuliidae) with and without exposure to Bacillus thuringiensis var. israelensis.

Behavioral time budgets were constructed for larval black flies of the Simulium jenningsi and S. tuberosum groups in a recirculating flume. Larvae spent the majority (54-80%) of time filter feeding. Flick rates of the labral fans, which averaged 0.7-1.9 flicks/sec, did not differ significantly between regimens of 0 mg/l and 10 mg/l of food. Larvae consistently flicked the fan nearest the water surface significantly more often than the lower fan. They also tended to flick the right fan more than the left, although this trend was significant in only one of four treatments. Although handedness cannot be dismissed, the differential flick rate appeared to be related to the position of the fans relative to the water surface, possibly because of different particulate concentrations in the microcurrents received by the upper and lower fans. Cessation of feeding by larvae of the S. jenningsi group from rivers regularly treated with Bacillus thuringiensis var. israelensis was independent of exposure to this biological control agent. Of larvae that ceased to feed, the mean time to cessation of feeding after exposure to Bti was 12-18 s, sufficient time to ingest a lethal dose.

Animals↗
PubMed2003

Review of blackfly (Diptera: Simuliidae) control in South Africa.

The medical, veterinary and economic importance of blackflies in South Africa, and the historical development of blackfly control programmes in various South African rivers, are reviewed in this paper. In 1996 it was estimated that blackflies can cause more than R 88 million damages per annum along the middle and lower Orange River where Simulium chutteri is considered the main pest species. A clear link between the construction of dams and the spread of the blackfly problem was shown. Four phases characterize the development of blackfly control in South Africa: (1) during the 1960s blackflies in the Vaal River were controlled with DDT; (2), during the 1970s and into the 1980s blackflies were controlled using water-flow manipulation; (3) when used at strategic times, water-flow manipulation could be used to enhance the effect of natural predator populations; and (4) during the 1990s the organophosphate temephos and toxins produced by the bacterium Bacillus thuringiensis var. israelensis were tested for their efficacy against blackflies. The larvicides temephos and B. thuringiensis proved to be effective and are still used in several control programmes. The latest research focuses on the factors that influence adult blackfly survival and annoyance, as well as the development of methods that can be used to protect sheep from blackfly attacks.

Animals↗
PubMed1983

Further studies on the development of onchocerca spp. (Nematoda: Filarioidea) in Nearctic black flies (Diptera: Simuliidae).

Of three species of Nearctic black flies tested, Simulium pictipes Hagen proved the most efficient laboratory vector of the bovine parasite Onchocerca lienalis. Among flies inoculated intrathoracially with 40 microfilariae, numbers of 3rd-stage larvae per fly were 7.63 for S. pictipes, 7.54 for S. vittatum Zetterstedt, and 0.83 for S. decorum Walker. S. pictipes survived the longest under laboratory conditions, with 83.3% of the females remaining alive 10 days after inoculation with 40 microfilariae of O. lienalis. Using an artificial membrane feeding system, S. pictipes could be routinely infected with O. lienalis by mouth. This black fly was also susceptible to infection with the Guatemalan strain of O. volvulus. Among flies injected with 10 microfilariae the rate of infection with 3rd-stage larvae was 93%, with a mean of three 3rd-stage larvae per fly. Successful techniques for the large-scale recovery and cryopreservation of 3rd-stage larvae of O. lienalis were also developed. A motility rate of 92.7% was observed in larvae cryopreserved within vector black flies.

Animals↗
PubMed2004

Preliminary studies on the biting activity and transmission of Onchocerca volvulus by Simulium neavei (diptera: simuliidae) in Kashoya-Kitomi focus, Western Uganda.

OBJECTIVE: To determine the biting activity and onchocerciasis transmission in Kashoya-Kitomi focus, Western Uganda. DESIGN: Cross-sectional survey in randomly selected sites. SETTING: Three districts in Western Uganda. METHOD: Crab trapping and examination for immature stages of Simulium neavei and full day human bait catches and dissections were conducted at three sites. RESULTS: A total of 338 crabs were caught and out of this 372 (95.9%) were positive with immature stages of S. neavei with mean S. neavei/crab of 6.9. High biting density of S. neavei was observed in the two sites in Kabarole and Mbarara districts whereas an extremely low density was observed at a site in Bushenyi. Diurnal biting pattern revealed two peaks in the morning (09:00-10:00 hours.) and in the late afternoon (14:00-15:00 hours.) with a mid-day lull. The infection/infective rates were 53.3/11.0%, 30.7% to 7.8% and 20.0/0% for sites in Mbarara, Kabarole and Bushenyi districts, respectively. Monthly biting rates/ Transmission potentials for Mbarara, Kabarole and Bushenyi districts were 6231/5437, 9244/2916 and 247/0. CONCLUSION: There was high transmission of onchocerciasis observed in Kashoya-Kitomi focus despite the ongoing ivermectin treatment. The need for improved chemotherapeutic coverage and instituting other control measures may be necessary.

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PubMed1999

Development of the first black fly (Diptera: Simuliidae) management program in Argentina and comparison with other programs.

In response to increasing pest populations of black flies, the government of Argentina initiated a pilot program to evaluate the effectiveness of larval control in the irrigation system of the Negro River Valley, an 18,240-km2 area in Patagonia. The extensive system of irrigation canals, drainage ditches, and natural waterways not only provides water for agriculture and general habitation but also affords habitat for immature black flies. Three species (Simulium bonaerense, Simulium wolffhuegeli, and Simulium nigristrigatum) are primary pests of humans and animals in this area. Trials were conducted using Vectobac AS in representative irrigation canals, a drainage ditch, and a medium-sized river. Most trials resulted in effective larval mortality and insecticide carry. Based on a comparison with 11 black fly suppression programs throughout the world, a suppression program for the Negro River Valley has a projected cost of approximately $1,623,360/year. This study represents the initial steps in development of the 1st areawide black fly suppression program in Argentina.

Animals↗
PubMed1999

[The karyotypic characteristics and chromosome polymorphism of three species of blood-feeding flies (Simuliidae, Diptera) inhabiting the Kola Peninsula and the Baikal Region].

Karyotypes of three species of black flies inhabiting the Kola Peninsula and the Baikal Region--Schoenbaueria pusilla, Gnus rostratum and G. decimatum--have been first described. The diploid number of these species is 2n = 6. The main identification signs of all chromosomes of the set were revealed and a high level of polymorphism in heterozygote inversions was found out. The detected heterozygote inversions are irregulary located in chromosomes, which is interpreted as an effective mechanism of populations highly adapted to different ecological conditions.

Animals↗
PubMed1999

Distribution of the larvae of blackflies (Diptera: Simuliidae) at Doi Inthanon National Park, northern Thailand.

The larvae of seventeen Simulium species consisting of thirteen known species, three unnamed species and one new species were distributed in various localities with different habitats at 400-2,460 meters above sea level in Doi Inthanon National Park, Chiang Mai Province, northern Thailand. Simulium caudisclerum, S. sp G and S. sp H were restricted to the high altitude of 2,460 m at the cool Ang Kha habitat of the summit of Doi Inthanon. On the other hand, S. nakhonense and S. rudnicki occurred only at low altitudes from 400 m-700 m. Some Simulium species such as S. fenestratum, S. asakoae, S. inthanonense and S. sp J were found in the warmer localities at 1,010 m-1,280 m altitudes. Moreover, S. feuerborni and S. rufibasis were widely distributed species at different altitudes from 700 m-2,460 m and 1,010 m-2,300 m respectively. Therefore, the distribution and abundance of Simulium species seem to correlate with altitudes as well as micro-habitat factors such as water temperature and water velocity.

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PubMed2001

[Triploidy in populations of three species of black flies of the genus Prosimulium roubaud (Diptera, Simuliidae)].

Karyotypes of 94 larvae belonging to species of black flies of the genus Prosimulium Rouband were studied on aceto-orcein stained squashes of 94 larvae belonging to three species of Prosimulium: P. isos Rubzov, P. pecticrassum Rubzov, and P. pamiricum Chubareva et Petrova. All the larvae appeared to be triploid parthenogenetic females, with no males being found. The structural peculiarities of these polytene chromosomes suggest a heterozygous nature of the examined larvae.

Animals↗
PubMed2001

Estimation of survival and gonotrophic cycle length of Simulium metallicum sensu lato (Diptera: Simuliidae) in southern Mexico.

This study compares the use of a mark-recapture analysis and a time-series analysis to estimate the gonotrophic cycle length and survivorship of Simulium metallicum s.l. in southern Mexico. Daily collections were performed with human- and horse-baited traps at 3 sites in a coffee plantation. The mark-recapture and time series experiments on these collections conclusively yielded a gonotrophic cycle length estimate of 3 days. Horizontal estimates of daily survivorship ranged from 0.75 to 0.69 and these values were similar to that estimated vertically of 0.77. The survival to infective stage (9 days) ranged from 0.012 to 0.043, taking into account at least 12 days for development of 3rd-stage larvae of Onchocerca volvulus. Mark-recapture and time-series methods were found to be suitable for estimating the gonotrophic cycle length and daily survivorship of S. metallicum s.l. under field conditions in southern Mexico.

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PubMed2003

[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).

Animals↗
PubMedDate not supplied

[An invasion of insect Simulium columbaczese (Diptera, Simuliidae) described in an old Romanian chronicle].

The oldest description of an invasion of Simulidae on the present territory of Romania, containing unique data for the history of parasitology in the Danube valley, has been discovered by the author in an anonymous chronicle "Istoria Tării Româneşti de la Octombrie 1688 până la Martie 1717 (History of Wallachia from October 1688 to March 1717), written at the Court of the Prince of Wallachia, Constantin Brâncoveanu. In the last decade of the XVIIth ctry, the Prince, at the head of his army, had to march in order to defend the Wallachian Danube border in the area of its gorges. The chronicle describes the delay caused on the way by an invasion of "poisonous" flies, attacking both animals and people. This description is detailed enough to establish that it is regarding an invasion of Simulium columbaczense, insect present in the area even nowadays. The development of these insects is favourised by numerous rivulets coming down mountain slopes of the Danube.

Animals↗
PubMedDate not supplied

[Results of a karyological study of blood-sucking flies (Diptera: Simuliidae) of Armenia].

Karyotypes of 31 species of black flies belonging to 11 genera have been examined. The morphology of polytene chromosomes from salivary glands of larvae and mitotic chromosomes of gonads and ganglia have been studied. It was found that most species have 2n = 6, except the Eusimulium species, which have 2n = 4. Each species is characterised by a specific pattern of polytene chromosomes. It was found that widely spread species are polymorphic in heterozygous inversions and additional B-chromosomes. The use of karyological studies in taxonomic diagnostics of black flies, especially in the cases when species are similar morphologically, was shown to be expedient.

Animals↗
PubMed2003

Susceptibility of black fly larvae (Diptera: Simuliidae) to lawn-care insecticides individually and as mixtures.

Urban and suburban watersheds have the potential to be highly impacted by chemicals, especially insecticides to control insect pests on lawns, ornamental plants, and home gardens. Three of the most common lawn-care insecticides detected in urban watersheds, carbaryl, chlorpyrifos, and malathion, have been evaluated using an acute orbital shaker toxicity test to determine their respective concentrations that produce 50% mortality (LC50) in Simulium vittatum Zetterstedt cytospecies IS-7 larvae. Results of the 48-h LC50 tests show chlorpyrifos to be the most toxic to black fly larvae (LC50 = 0.28 microg/L) followed by carbaryl (LC50 = 23.72 microg/L) and malathion (LC50 = 54.20 microg/L). These insecticides were also tested as binary and ternary mixtures using the toxic unit (TU) approach. Toxicity was shown to be greater than additive for the ternary mixture of chlorpyrifos-carbaryl-malathion (LC50 = 0.56 TU) and the binary mixtures of chlorpyrifos-malathion (LC50 = 0.72 TU) and carbaryl-malathion (LC50 = 0.78 TU). The binary combination of chlorpyrifos and carbaryl was shown to be additive (LC50 = 0.98 TU). These results indicate that aquatic invertebrate populations in urban and suburban streams may experience a higher-than-expected increase in toxicity-related effects when all three chemicals are present in the waterway.

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PubMedDate not supplied

[An analysis of the morphometric traits of the pupae of 3 populations of Testisimulium kondici (Diptera: Simuliidae)].

In the pupae of three populations of Testisimulium kondici (Bar.) the variations of nine quantitative characters are determined. The discrepancies between these populations are analyzed. With the help of statistical indices the specific distinctions of one of the studied populations from two others, which are not essentially different, is established. Earlier (Kachvorian, 1989; Kachvorian and Tonoian, 1990) karyological and phenotypical differences between the larvae of these populations were found. Considering that the isolated population develops under anthropogenic influence a link between the above discrepancies and this influence is assumed to exist.

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