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Bioassay of some Egyptian isolates of Bacillus thuringiensis against Culex pipiens (Diptera: Culicidae).

Some Egyptian isolates of Bacillus thuringiensis (BT) were grown on economic media contain 4% of fodder yeast in tap water and incubated under shaking conditions for four days. The biological activities of these isolates against Culex pipiens (Diptera: Culicidae) were carried out to determine their effectiveness against field and laboratory strains of 3rd larval instar. All isolates of BT were more pathogenic to laboratory strain. causing up to 84% larval mortality. The insecticidal activities of these isolates were extended to the pupal stage causing a significant effect on pupal mortality in both strains tested. A pronounced effect on adult emergence was noticed with remarkable adult malformations especially in the case of the isolate No. 2. The reproductivety of females was affected significantly by all isolates applied.

Animals↗

[Chromosomal polymorphism of the unique Baikal deep-water population of Sergentia flavodentata (Diptera, Chironomidae) from the region of hydrothermal venting].

The subject of this study is chromosomal polymorphism of a population of Baikal endemic species Sergentia flavodentata (Diptera, Chironomidae) from the Frolikh Bay region of hydrothermal venting at a depth of 420-430 m. In 35-67% of larvae, six heterozygous inversions were found to be preserved for 13 years (materials of 1991, 1994, 1996, 1999, 2003). The number of zygotic combinations reached 14; 0.5-0.7 inversions per individual was observed. It is suggested that stable chromosomal polymorphism characteristic of this species is nonrandom, being a mechanism of the population adaptation to the specific conditions of hydrothermal venting community based on bacterial biochemosynthesis.

Adaptation, Physiological↗

Evaluation of the naturally-derived insecticide spinosad against Culex pipiens L. (Diptera: Culicidae) larvae in septic tank water in Antalya, Turkey.

The naturally-derived insecticide spinosad (Conserve SC) was evaluated against larval Culex pipiens L. (Diptera: Culicidae) under laboratory and field conditions in Antalya, Turkey. Laboratory bioassays showed that the 24 h LC50 and LC90 against late 3rd and early 4th instars were estimated at 0.027 and 0.111 parts per million, respectively, while adult emergence was eliminated at concentrations above 0.06 ppm. Larval mortality from septic tanks that were treated with spinosad at rates of 25, 50, 100, and 200 g ai/ha ranged between 22 to 78% 1 day after application. At 7 days post-treatment, larval mortality ranged from 2 to 50% and at 14 days mortality was <10% for all treatments. Larval bioassays of the water from those septic tanks treated at 100 and 200 g ai/ha resulted in an elimination of Cx. pipiens larvae 7 days after treatment. After this time, larval reduction declined to 79 and 83%, respectively, 14 days after treatment. Larval reduction in septic tanks treated at the two lowest rates (i.e. 25 and 50 g ai/ha) ranged from 14 to 74% during the 14-day study. These results indicated that spinosad can be considered an effective larvicide for treatment of septic tanks against Cx. pipiens.

Animals↗

[Population dynamics of Bactrocera dorsalis (Diptera: Tephritidae) in Xishuangbanna of Southern Yunnan].

In the study, an all year round monitoring through lure-traps in 1997, 2000 and 2003 was conducted on the population dynamics of oriental fruit fly, Bactrocera dorsalis (Diptera: Tephritidae) in Xishuangbanna of Southern Yunnan, and the factors in relation with its population fluctuation, including temperature, rainfall, and host species were analyzed. The fruit fly occurred year-round in Xishuangbanna, with a low population level from November to February, and increased steadily from March to July or August. An increasing peak appeared in July or August, depending on the rainfall amount in that year. Afterwards, the fly population declined markedly until to October. Temperature, rainfall, and host fruits were supposed to be the major factors affecting the population fluctuation. The monthly average temperature in Xishuangbanna was in the ranges suitable for the development and reproduction of the fly, but the monthly average minimum temperature from December to February appeared to be lower than the suitable temperature, which was suggested to be responsible for the low populations in the winter months. Rainfall was another essential factor affecting population fluctuation. The population was depressed when the monthly rainfall amount was lower than 50 mm, but increased when the amount ranged between 100 and 200 mm. Under conditions the monthly rainfall amount was higher than 250 mm, the fruit fly population was reduced markedly, which explained the decreasing population in July or August when the heavy rain occurred. Mango, orange, pear, longan, and peach were the main host species of the fly, among which, mango and longan were most preferred by the fly. Therefore, their planted area, fruiting period and productivity exerted essential effects on the fly population fluctuation, and regarded as another major factor affecting the fly population in this area.

Animals↗

[New evidence for mass reproduction of midges (Diptera, Simuliidae) in the Voronezh Region].

In the forest-steppe zones, the bloodsucking dipterans--midges (Diptera, Simuliidae)--tend to drastically increase in size, which poses medical and veterinary problems (the toxic saliva administered into the victim's body on blood sucking causes diseases in man, disability, and even animals' death). According to our data, the role of dominating bloodsuckers varies in different districts of the Voronezh Region, depending on their Iocal conditions (the types of water systems and landscapes).

Animals↗

Relative abundance of mosquito species (Diptera: Culicidae) on Big Pine Key, Florida, U.S.A.

Species diversity of mosquito (Diptera: Culicidae) collections in carbon dioxide-baited light traps was investigated on Big Pine Key, Florida, from 2000 - 2004. Twenty species of mosquitoes were collected during this study, the most commonly collected being Anopheles atropos, Culex bahamensis, Deinocerites cancer, and Ochlerotatus taeniorhynchus. Ochlerotatus taeniorhynchus is the dominant species at this location. For most of the mosquito species, more individuals were collected during the "high season" months (June to September) than in the "low season" months (January to March). During most years more mosquito species were collected in the high season than in the low season. Rank order of species collected was significantly correlated between low and high season. Species composition at this site appears to be relatively stable from year to year and from season to season.

Animals↗

Laboratory estimation of degree-day developmental requirements of Phlebotomus papatasi (Diptera: Psychodidae).

Cutaneous leishmaniasis is one of the most important vector-borne endemic diseases in Turkey. The main objective of this study was to evaluate the influence of temperature on the developmental rates of one important vector of leishmaniasis, Phlebotomus papatasi (Scopoli, 1786) (Diptera: Psychodidae). Eggs from laboratory-reared colonies of Phlebotomus papatasi were exposed to six constant temperature regimes from 15 to 32 degrees C with a daylength of 14 h and relative humidity of 65-75%. No adult emergence was observed at 15 degrees C. Complete egg to adult development ranged from 27.89 +/- 1.88 days at 32 degrees C to 246.43 +/- 13.83 days at 18 degrees C. The developmental zero values were estimated to vary from 11.6 degrees C to 20.25 degrees C depending on life stages, and egg to adult development required 440.55 DD above 20.25 degrees C.

Animals↗

Isolation of Tahyna virus from biting midges (Diptera, Ceratopogonidae) in Czecho-Slovakia.

A total of 14,250 haematophagous biting midges (genus Culicoides, Diptera: Ceratopogonidae) were collected in June 1986 in the mountains Ceskomoravská vysocina (about 600 m above sea level); from these 2 strains of Tahyna virus (serogroup California, Bunyaviridae) were isolated. To our knowledge this is the first isolation of a California serogroup virus from the species of family Ceratopogonidae as well as the first report of arbovirus isolation from biting midges in Europe.

Animals↗

Molecular phylogeny of the subfamily Tephritinae (Diptera: Tephritidae) based on mitochondrial 16S rDNA sequences.

The phylogeny of the subfamily Tephritinae (Diptera: Tephritidae) was reconstructed from mitochondrial 16S ribosomal RNA gene sequences using 53 species representing 11 currently recognized tribes of the Tephritinae and 10 outgroup species. The minimum evolution and Bayesian trees suggested the following phylogenetic relationships: (1) monophyly of the Tephritinae was strongly supported; (2) a sister group relationship between the Tephritinae and Plioreocepta was supported by the Bayesian tree; (3) the tribes Tephrellini, Myopitini, and Terelliini (excluding Neaspilota) were supported as monophyletic groups; (4) the non-monophyletic nature of the tribes Dithrycini, Eutretini, Noeetini, Tephritini, Cecidocharini, and Xyphosiini; and (5) recognition of 10 putative tribal groups, most of which were supported strongly by the statistical tests of the interior branches. Our results, therefore, convincingly suggest that an extensive rearrangement of the tribal classification of the Tephritinae is necessary. Since our sampling of taxa heavily relied on the current accepted classification, some lineages identified by the present study were severely under-sampled and other possible major lineages of the Tephritinae were probably not even represented in our dataset. We believe that our results provide baseline information for a more rigorous sampling of additional taxa representing all possible major lineages of the subfamily, which is essential for a comprehensive revision of the tephritine tribal classification.

Animals↗

Effect of abiotic factors on seasonal population dynamics of Lutzomyia longipalpis (Diptera: Psychodidae) in northeastern Brazil.

The resurgence of visceral leishmaniasis in Brazil increases the need for studies to elucidate the spatial and temporal dynamics of Lutzomyia longipalpis (Lutz and Neiva) (Diptera: Psychodidae), the vector of Leishmania infantum, the causative agent of visceral leishmaniasis in Brazil. Sand flies were captured in peridomestic habitats biweekly for 3 yr. Cross-correlation tests and spectral analysis were used to analyze the simultaneous and lag-time correlations between Lu. longipalpis population densities and abiotic factors of temperature, relative humidity, wind velocity, and rainfall. Distinct seasonal patterns were observed for males and females, with intervals of 6 mo between population peaks for males and 12 mo for females. Peak female population densities lagged 3 mo behind the maximum annual temperature. Female population density was negatively correlated with relative humidity. An increase in average wind velocity was followed by a decrease in the number of females for 2 wk. Understanding the relationship between the seasonal population dynamics of Lu. longipalpis and abiotic factors will contribute to the design of better control measures to decrease transmission of L. infantum and consequently the incidence of leishmaniasis.

Animals↗

Naive and conditioned responses of Culex pipiens pipiens biotype molestus (Diptera: Culicidae) to flower odors.

Flower odors are important signals for chemical communication between plants and flower visitors. Here, we studied the naive responses of Culex pipiens pipiens biotype molestus Forskal 1775 (Diptera: Culicidae) to typical flower odors and assessed the learning capacity of mosquitoes to floral volatiles. The odor compounds used in the bioassay, phenyl acetaldehyde, veratrole, and 2-methoxyphenol, are typically found in the floral odor of Silene otites (L.) Wibel, a plant that is pollinated by nectar-drinking mosquitoes and moths, and/or in other closely related Silene species. Wind tunnel bioassays with a mixture of these compounds revealed that attraction of mosquitoes to odors was positively correlated with time passed since the last feeding. In single component bioassays, mosquitoes showed strong innate responses to phenyl acetaldehyde and only moderate or weak responses to veratrole and 2-methoxyphenol. Furthermore, in comparison with naive mosquitoes, conditioned mosquitoes were significantly more attracted to the mixture and single volatiles. These results indicate that naive mosquitoes are effectively attracted by appropriate floral scent compounds and that learning can increase the attractiveness of these compounds.

Acetaldehyde↗

Selection of insensitive acetylcholinesterase as a resistance mechanism in Aedes aegypti (Diptera: Culicidae) from Santiago de Cuba.

A sample of Aedes aegypti (L.) (Diptera: Culicidae) from Santiago de Cuba, Cuba, with a high level of propoxur resistance compared with the reference susceptible Rockefeller strain (12.60 x at the 50% lethal concentration [LC50] and 18.08 at the 90% lethal concentration [LC90]), with a 4.3% frequency of insensitive acetylcholinesterase (AChE) frequency, was subjected to propoxur selection for 13 successive generations to increase the frequency of this resistance mechanism in Ae. aegypti. High resistance to propoxur was developed during this selection (41.73-fold), and the frequency of insensitive AChE mechanism was increased 13.25-fold. Other mechanisms (overproduced esterases, glutathione transferases, or monooxygenases) were not detected in the propoxur-selected strain. The selection of an insensitive AChE resistance mechanism in Ae. aegypti has important implications and will be a valuable resource for genetic studies and molecular characterization of the ace gene mutation(s) associated with insecticide resistance in Ae. aegypti.

Acetylcholinesterase↗

The spermatozoon of Phlebotominae sandflies (Diptera, Psychodidae).

Spermatozoa of Sergentomyia minuta Rondani were examined by light, scanning and transmission electron microscopy. The spermatozoon was seen to have a head and a tail. The first was characterized by an acrosomal complex with a thin space containing granular material which was interpreted as a perforatorium. The tail contained a 9+9+0 axoneme and one mitochondrial derivative. These results were compared with the sperm ultrastructure of other Diptera, particularly Psychodidae.

Animals↗

[Entomological survey of sandflies (Diptera, Psychodidae) in the province of L'Aquila (Abruzzo)].

A survey on phlebotomine sandflies (Diptera, Psychodidae) was carried out in the province of L'Aquila, Abruzzo region (Italy). Ten collecting sites at altitudes between 700 and 1,070 m a.s.l., produced a total of 324 specimens (81.1% males), 72.86% being Phlebotomus perniciosus, 3.08% P. mascittii, 0.30% P. papatasi and 23.76% Sergentomyia minuta. The collecting sites at 1,070, 950 and 775 m a.s.l. are the highest levels recorded in Italy for P. perniciosus, P. mascittii and P. papatasi, respectively. P. perfiliewi, the proven vector of cutaneous leishmaniasis (CL) in the Abruzzo region (Maroli et al., 1987) was absent. The probable role of P. perniciosus in the transmission of the sporadic CL cases reported from the area is discussed.

Animals↗

Separation of female Psychodopygus wellcomei and P. complexus (Diptera: Psychodidae) by cuticular hydrocarbon analysis.

Psychodopygus wellcomei (Diptera: Psychodidae), vector of Leishmania braziliensis braziliensis - causative agent of cutaneous leishmaniasis in Brazil, cannot be distinguished from sympatric P. complexus either by morphometrics or isoenzyme profiles. We report here the use of cuticular hydrocarbon analysis in the successful separation of individual female P. wellcomei and P. complexus. This technique involves the use of gas liquid chromatography and discriminant function analysis.

Animals↗

[Effect of delta-endotoxin of Bacillus thuringiensis israëlensis on biochemical functional relationships in Diptera Aedes aegypti].

A study of the action of very low doses of the delta-endotoxin of Bacillus thuringiensis israëlensis on the larvae of Aedes aegypti (Diptera) gave evidence for peculiar properties of the dose/effect relations based on the variations of the regression slopes of functional relationships between the pairs cysteine/serine and fatty acids/histidine, by contrast with the pair fatty acids/glucose which exhibited a classical shaped relation. This indicates "crypto-toxicological" processes, not lethal by themselves and without pathological symptoms, but able to initiate "pathogen-chaining" mechanisms leading, at the end, to a lethal secondary syndrome.

Aedes↗