Biological studies on adult water snipe fly,Atherix ibis (Fabricius, 1798) (Diptera: Athericidae): old myths and new facts

The water snipe fly, Atherix ibis, is known for its eggbearing females aggregating in clusters. They are most frequently found as flat crusts under the outer parts of bridge ceilings above the water. There is no persistent pattern in the cluster distribution either in relation to the current direction or to the sun. Females aggregate in early summer in short periods of warm and calm weather only. Females are attracted to an aggregation site, probably by pheromones. The flies fasten to the surface and to each other by minute Velcro-like structures on their feet. The eggs are shed inside the cluster. After 9–12 days the eggs hatch, and the larvae leave clusters and drop into the water. There is no increased temperature inside the cluster. There are no signs of larval feeding on either dead flies or siblings in the cluster. The majority of larvae leave the cluster during night time, also when the normal day–night rhythm is eliminated by experimental black-out.     

Novel spirochetes isolated from mosquitoes and black flies in the Czech Republic

During the years 1999–2002, a total of 4,898 individuals of 26 species of hematophagous insects (4,149 mosquitoes, 583 black flies, and 166 tabanid flies) was examined for the presence of spirochetes using dark‐field microscopy. There was an overall recovery of spirochetes from the midguts of Culicidae and Simuliidae of 23.5% and 11.4%, respectively. Spirochetes were not detected in Tabanidae. Seven spirochetal strains have been successfully recovered from mosquitoes and black flies: BR149 (Culex pipiens), BR151 (Cx. pipiens), BR173 (Cx. pipiens), BR177 (Cx. pipiens), BR193 (Aedes cinereus), BR208 (Cx. pipiens), and BR231 (Simulium noelleri). The strains have been adapted to laboratory conditions (BSK‐H Complete medium). Their preliminary determination based on 16S rRNA gene sequencing has shown that they differ from the Lyme disease spirochete Borrelia burgdorferi sensu lato as well as other members of the Order Spirochaetales indicating novel bacterial species in the Family Spirochaetaceae.     

EDTA-assisted heavy-metal uptake by poplar and sunflower grown at a long-term sewage-sludge farm

Little information is available concerning the efficacy of chelates applied to biosolids (sewage-sludge)-treated soil for heavy-metal removal. The purpose of the experiment was to determine the availability to sunflower (Helianthus annuus L.) and hybrid poplar (Populus deltoides Marsh. × P. nigra L.) seedlings, of non-essential (Cd, Ni, Pb) and essential heavy metals (Cu, Fe, Mn, Zn) in field soil injected with biosolids since 1976 and treated with ethylenediamine-tetraacetic acid (EDTA) in 2001. Sunflower was grown at two densities, 20000 and 60000 plants/ha, and poplar at 10000 plants/ha. The tetrasodium salt of EDTA was applied at rates of 0, 0.5, 1, and 2 g EDTA salt per kg surface (25-cm depth) soil. The EDTA did not affect uptake by poplar of the three non-essential (Cd, Ni, Pb) and four essential (Cu, Fe, Mn, Zn) heavy metals. For sunflower, the 1.0 g/kg rate of chelate addition resulted in maximal removal of the three non-essential heavy metals (Cd, Ni, Pb). Uptake of the essential heavy metals by sunflower was little affected by the EDTA. At the 20000 plants/ha density, leaves of sunflower grown with 1.0 g EDTA Na₄2H₂O per kg soil accumulated more Cd, Ni, and Pb than leaves of sunflower grown without the EDTA salt. At this density, concentrations of Cd in leaves of sunflower without EDTA and with 1.0 g/kg EDTA salt were 2.2 and 6.5 g/g, respectively; for Ni, they were 6.7 and 19.2 g/g, respectively; and for Pb, they were 15.6 and 46.9 g/g, respectively. At the 60000 plants/ha density, stems of sunflower grown with 1.0 g EDTA Na₄2H₂O per kg soil accumulated more Cd, Ni, and Pb than stems of sunflower grown without the EDTA salt. At this density, concentrations of Cd in stems of sunflower without EDTA and with 1.0 g/kg EDTA salt were 0.6 and 4.6 g/g, respectively; for Ni, they were 1.7 and 17.6 g/g, respectively; and for Pb, they were 5.2 and 42.8 g/g, respectively. Removal of the non-essential heavy metals by sunflower was greater at the higher plant density (60000 plants/ha) compared to the lower one (20000 plants/ha).     

Sexual selection in the gift-giving dance fly, Rhamphomyia sulcata, favors small males carrying small gifts

In some species of insects males transfer a gift to females during courtship or copulation. In the dance flies these nuptial gifts vary from nutritious prey items to inedible tokens such as a leaf, stone, or silk balloon. Nuptial gifts in dance flies are presumed to increase male mating success. We examined the strength and form of sexual selection on male Rhamphomyia sulcata, an empidid in which males provide females with a nutritious prey item as a nuptial gift. We found that whereas large males carried large gifts, neither large males nor gifts were targets of sexual selection. Indeed, correlational selection analysis and nonparametric examination of the fitness surfaces revealed that small males carrying small gifts were the most successful. Males may be more maneuverable or flight efficient with small gifts, or small males with large gifts may be unable to carry both a large gift and a female in the paired descent flight. These results suggest carrying constraints may be an important factor in determining selection on nuptial gift size. The largest target of sexual selection was old males. Old males were also paired with the largest and most fecund females, highlighting the role mate quality can further contribute to selection on males. Correlational selection analysis also revealed selection for an increase in covariance between male wing length and body size, and for an increase in slope between these traits. Males who deviate away from the optimal phenotypic relationship for two tightly related morphological traits, such as tibia and wing length, may have overall reduced performance. These findings highlight the role correlational sexual selection can play in optimizing nonsexual male morphology and scaling relationships. This study questions the role of the nuptial gift in dance flies as a resource for females.     

Microsatellite diversities and gene flow in the tsetse fly,Glossina morsitans s.l

Tsetse flies occupy discontinuous habitats and gene flow among them needs to be investigated in anticipation of area-wide control programs. Genetic diversities were estimated at six microsatellite loci in seven Glossina morsitans submorsitans Newstead (Diptera: Glossinidae) populations and five microsatellite loci in six G. m. morsitans Westwood populations. Nei's unbiased diversities were 0.808 and 76 alleles in G. m. submorsitans and 0.727 and 55 alleles in G. m. morsitans. Diversities were less in three laboratory cultures. Matings were random within populations. Populations were highly differentiated genetically. Populations were strongly subdivided, as indicated by fixation indices (F(ST)) of 0.18 in G. m. morsitans and 0.17 in G. m. submorsitans. 35% of the genetic variance in G. m. submorsitans was attributed to differences between populations from The Gambia and Ethiopia. All available genetic evidence suggests that genetic drift is much greater than gene flow among G. morsitans s.l. populations.     

Mosquito Control Evaluations of an Insect Growth Regulator, Pyriproxyfen against Culex pipiens pattens (Diptera, Culicidae) Larvae in Marsh Area, Korea

ABSTRACT Mosquito control evaluations of the granular formulation of 0.5% pyriproxyfen were undertaken in marshes and a pond in Busan during the period of July through September, 2001. In marsh condition where Culex pipiens pattens were predominantly breeding, the treatment of pyriproxyfen produced over an average of 95% mosquito larval reduction at a concentration of 0.05 mg/1 for the first 4 weeks in spite of heavy precipitation (total 274.4 mm) during the period. Reduction rates of 72.6% and 32.3% appeared in the 5th and 7th weeks probably due to heavy input of sewage and flood. However, the reduction rate increased again at the 8th week, showing a 94.5% reduction, probably because of the slow releasing of pyriproxyfen granular formulation. In the second treatment of pyriproxyfen, complete mortality was obtained at the 1st and 3rd weeks. Also, a satisfactory level of Cx. pipiens larval reduction of 96.6% was observed at the 4th week. In a pond assessment, the treatment of pyriproxyfen at a concentration of 0.05 mg/1 produced a complete reduction of Cx. pipiens pattens from the 1st week through the 4th week after treatment. In the second treatment, 100.0% reduction was obtained at the 1st and 2nd weeks in the same sites. The treatment resulted in 84.4% and 97.9% reduction of mosquitoes at the 3rd and 4th weeks, respectively.     

Classification and ordination of plant formations in the Pantanal of Brazil

Classification and ordination of plant formations are presented for a seasonally flooded plain of the Brazilian Pantanal. Phytosociological data were collected on 10 physiognomically distinct formations during the rainy, flood, and dry seasons. The degree of association among plant species was measured with Jaccard similarity index, and both Jaccard similarity index and Bray Curtis distance index were employed to classify sample units into similar groups. The ordination of plant species and sample units were performed with Correspondence Analysis. Four groups of plant formations were significantly distinct on a quantitative basis: marsh ponds/waterlogged basins, short grasslands, tall grassland/scrub, and forest-edges. These formations were ordered along a gradient of topographic relief from depressions with permanent standing water (marshes) through flats subject to seasonal flooding (grasslands and scrub) and mounds of sandy soil above the flood level (forests). Although hydroperiod appears to be one of the most important variables, the distribution of plant species within wetlands is most probably explained by the interaction of many additional factors. A few plant species could be used as indicators of the local hydrological and edaphic conditions, e.g., Eleocharis elegans, Aeschynomene fluminensis, Hydrolea spinosa, and Hymenachne amplexicaulis for marsh ponds, and Caperonia castaneifolia, Diodia kuntzei, and Eleocharis acutangula for waterlogged basins. The procedure presented in this study could be developed as a tool for the inventory and management of the Pantanal and other palustrine wetland habitats.     

Performance and feeding behavior of Ceratitis capitata: comparison of a wild population and a laboratory population

Experiments were carried out to test the performance and some aspects of feeding behavior in two populations of Ceratitis capitata (a population reared in the laboratory for 16 years, i.e., approximately 160 generations, and a wild one obtained from infested coffee, Coffea arabica grains). Two types of food were used in the experiment: an artificial yeast diet used for laboratory rearing and papaya (Carica papaya), a natural host of the fly. The performance parameters tested were percent emergence, time to emergence, adult female size, and egg production during the pre-oviposition phase (first five days of adult life). The behavioral aspects tested were food preference by newly hatched larvae, induction, estimated ingestion of the two diets, whether the larvae placed on one diet stayed there or moved to the other diet, and acceptance of food for oviposition. The results indicated that the performance of the wild population was superior when the flies fed on papaya, whereas the performance of the laboratory population was similar with the two diets; the wild population showed a strong preference for papaya in all choice experiments, whereas the laboratory population showed no diet preference; the females of the wild population only oviposited on pieces of papaya that had not been peeled, and did not oviposit in the artificial diet; the females of the laboratory population oviposited indiscriminately on unpeeled and peeled papaya and on the artificial diet.     

Factors affecting the efficacy of three commercial formulations of Bacillus thuringiensis var. israelensis against species of European black flies

The efficacy of three commercial formulations of Bacillus thuringiensis var. israelensis against two European black fly species was determined. The effect of seston concentration, temperature and larval size on the efficacy of the formulations was also determined. Teknar‐WDC was found to be almost four times as effective as Bactimos‐WP though only slightly more efficient than Vectobac‐AS against Simulium variegatum gp. larvae. Small larvae ( < 2.5 mm) were more susceptible to both Teknar‐WDC and Vectobac‐AS than large larvae ( > 5 mm) though no difference was seen with Bactimos‐WP. High seston concentrations both before and during bioassays significantly decreased the efficacy of all formulations. Increased temperatures increased the efficacy of all formulations.