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At least 253 records · Page 14Linked to original sources
PubMed1962

The identification of infective filarial larvae in Simuliidae.

Although it is recognized that the presence of animal filariae can lead to confusion in the interpretation of infection rates in mosquito vectors of filariasis, the filariae found in man-biting simuliids are usually assumed to be Onchocerca volvulus. The authors of this paper emphasize that it is unwise to calculate transmission indices from infection rates in man-biting simuliids unless there is confidence in the identification of the filarial larvae. In this respect they cite their observations on Mount Elgon in Uganda which show that the majority of the filarial larvae in Simulium neavei-the local vector of onchocerciasis-are of species that do not affect man.To assist in the correct interpretation of infection rates in the vectors the authors made a detailed study of the morphological character of O. volvulus infective larvae and established criteria for distinguishing O. volvulus from other filariae known to be transmitted by simuliids.

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PubMed1992

Efficacy of Bacillus thuringiensis var. israelensis against larvae of the southern buffalo gnat, Cnephia pecuarum (Diptera: Simuliidae), and the influence of water temperature.

Susceptibility of southern buffalo gnat larvae to Bacillus thuringiensis var. israelensis (B.t.i.) was studied during 1986-88. Tests were conducted using Vectobac 12AS in a mini-gutter aquatic bioassay system. Mini-gutter tests using a 4.5 ppm B.t.i. concentration and a 10 min exposure period confirmed a positive correlation between water temperature and B.t.i. effectiveness. Significantly lower larval mortality occurred as water temperature decreased below 9 degrees C, indicating that proper timing of B.t.i. application is essential to maximize larval control. Even with this temperature limitation, larval control using B.t.i. should provide an economically effective means of preventing outbreaks of the southern buffalo gnat.

Animals↗
PubMed1992

An episode of resistance to permethrin in larvae of Simulium squamosum (Diptera: Simuliidae) from Cameroon, after 3 1/2 years of control.

Because of the biting nuisance from females of Simulium squamosum, a 30 km section of the Sanaga River (Cameroon) was treated since 1987 with permethrin for the control of larval populations. In 1990, resistance to permethrin occurred in a small proportion of the larvae, with a resulting 2-4x increase of the LC95 for dead larvae (moribund larvae considered as live). In 1991, after a 6-month interruption of the treatments, susceptibility to permethrin returned to the initial level, and was similar to the susceptibility of S. squamosum larvae from a non-treated section of the Sanaga. In the context of a small-scale control program, resistance to permethrin can be reversible, and it can be avoided by rotation with other types of insecticides such as Bacillus thuringiensis serovar, israelensis.

Animals↗
PubMed1992

New self-marking device for dispersal studies of black flies (Diptera: Simuliidae).

An effective and inexpensive device is described for marking newly emerged black flies with fluorescent dust. Survival of marked adults of Simulium venustum s.l. and Stegopterna mutata s.l. did not differ significantly from unmarked individuals over a 5-day period. Marked individuals were attracted to human hosts in landing biting tests, and the portions of the self-marking trap lying just above the water surface did not appear to significantly hamper black fly emergence success.

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PubMed2004

Distribution and seasonal abundance of Cnephia pecuarum (Diptera: Simuliidae) in Arkansas.

Studies were conducted during 1990-92 to determine the distribution and abundance of the southern buffalo gnat (Cnephia pecuarum) in Arkansas. Field collection of adults near streams throughout Arkansas demonstrated adult occurrence in 24 counties. Abundance studies were conducted by using tent traps baited with dry ice in 3 counties in southeastern Arkansas. In 1990, studies were conducted in Bayou Meto (Ashley County); Seven Devils Swamp (Drew County); and Crocketts Bluff, Bayou Meto, and Little LaGrue Bayou (Arkansas County). During 1991 and 1992, abundance studies were limited to Arkansas County. Results and previous field observations suggest 3 distinct populations in Arkansas (southwestern, southeastern, and central). Seasonal occurrence extended from December to April but varied by location and year. Abundance studies indicated variation in both seasonal occurrence and adult density by year and trap location. Although investigations during 1990-91 showed similar seasonal occurrence trends (peaking in early March), higher adult densities were noted during 1990. In contrast, peak adult density during 1992 occurred in late January. Greatest adult density during the course of these investigations was 7,160 gnats/24 h during 1990 at Crocketts Bluff (Arkansas County). Results suggest that additional studies are warranted to determine the impact of environmental and river factors on seasonal occurrence and abundance of this pest.

Animals↗
PubMed2004

Testing hypotheses on egg number and size in black flies (Diptera: Simuliidae).

Field-collected gravid females were used to test a series of inter- and intraspecific hypotheses on egg size and number in 23 species of black flies. Qualitative differences between bird and mammal blood did not result in significant differences with respect to fecundity properties. The five species with overwintering larvae produced more eggs than did the 18 species with overwintering eggs. Contrary to prediction, egg size was correlated significantly with body size in only two of 17 examined species; indeed, in three species this relationship was negative. However, the association between female size and egg number within species was positive. Strong support was found for a tradeoff between egg size and number across species but not within species. The present study shows similarities with other dipterans but also substantial variability, probably reflecting a high degree of flexibility. The results are primarily discussed in an evolutionary context, but they also provide useful information for black fly management.

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PubMed1992

Impact of the black fly (Diptera: Simuliidae) control agent Bacillus thuringiensis var. israelensis on chironomids (Diptera: Chironomidae) and other nontarget insects: results of ten field trials.

Except for moderate mortality among filter-feeding chironomids, Rheotanytarsus spp., the results of 10 field trials with Bacillus thuringiensis var. israelensis (B.t.i.) indicated a wide margin of safety to the chironomid community and other stream nontarget insects. Mayflies, caddisflies and 2 other types of chironomids, i.e., tube-dwelling (Chironominae) and surface-dwelling, caseless larvae (mix of Chironominae, Diamesinae, Orthocladiinae, Tanypodinae), did not appear to be affected. The susceptibility of filter-feeding chironomids was considerably less than black flies; for example, 4 months of data collected during an operational black fly control program indicated a mean (+/- 95% CI) mortality among Rheotanytarsus larvae of 23 (15-32)% vs. 98 (97-99)% among black flies. Although clearly demonstrating the potential of adverse impact on filter-feeding chironomids in operational black fly programs, these trials also confirmed the narrow impact of B.t.i. on the overall stream insect community.

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