Culicoides Brevitarsis Research Articles

The potential for bluetongue virus serotype 16 to cause disease in sheep in New South Wales, Australia.

BLUETONGUE VIRUS SEROTYPE 16 DETECTION IN NSW: In coastal New South Wales (NSW), bluetongue virus (BTV) serotypes 1 and 21 are endemic and transmitted in most years without evidence of disease. However, serotype 16 (BTV-16) infection was detected for the first time in NSW in November 2016 in cattle undergoing testing for export. Retrospective testing of blood samples collected from sentinel cattle as part of the National Arbovirus Monitoring Program (NAMP) established that the first detected transmission of BTV-16 in NSW occurred in April 2016 in sentinel cattle on the NSW North Coast. Subsequently, until 2022, BTV-16 has been transmitted in most years and was the predominant serotype in the 2018-2019 transmission season. The data available suggests that BTV-16 may have become endemic in NSW. EXPERIMENTAL STUDIES: During experimental infection studies with BTV-16, all sheep were febrile, with the peak of viremia occurring 6-10 days after inoculation. There was nasal and oral hyperaemia in most sheep with several animals developing a nasal discharge and nasal oedema. All sheep developed coronitis of varying severity, with most also developing haemorrhages along the coronary band. There was a high incidence of haemorrhage in the pulmonary artery, epicardial petechiae, extensive pericardial haemorrhages and moderate body cavity effusions including pericardial effusions. CONCLUSION: Overall, experimental pathogenicity findings suggest moderate disease may occur in sheep in the field. These findings, when combined with climatic variability that could result in an expansion of the range of Culicoides brevitarsis into major sheep-producing areas of the state, suggest that there is an increasing risk of bluetongue disease in NSW.

Spatial and temporal distribution of Culicoides species in the New England region of New South Wales, Australia between 1990 and 2018.

Culicoides are one of the smallest hematophagous flies measuring 1–5 mm in size with only females seeking blood for egg development. The present study investigated spatio-temporal distribution of Culicoides species trapped between 1990 and 2018 at 13 sites in the New England region of NSW, Australia using automated light traps. Trapping locations were divided into three subregions (tablelands, slopes and plains). Nineteen Culicoides species were identified. Culicoides marksi and C. austropalpalis were the most abundant and widespread species. Culicoides brevitarsis, the principal vector of livestock diseases in New South Wales comprised 2.9% of the total catch and was detected in 12 of the 13 locations in the study. Abundance as determined by Log10 Culicoides count per trapping event for the eight most abundant species did not vary significantly with season but trended towards higher counts in summer for C. marksi (P = 0.09) and C. austropalpalis (P = 0.05). Significant geographic variation in abundance was observed for C. marksi, C. austropalpalis and C. dycei with counts decreasing with increasing altitude from the plains to the slopes and tablelands. Culicoides victoriae exhibited the reverse trend in abundance (P = 0.08). Greater abundance during the warmer seasons and at lower altitudes for C. marksi and C. austropalpalis was indicative of temperature and rainfall dependence in this region with moderate summer dominance in rainfall. The Shannon-Wiener diversity index of species was higher on the tablelands (H = 1.59) than the slopes (H = 1.33) and plains (H = 1.08) with evenness indices of 0.62, 0.46 and 0.39 respectively. Culicoides species on the tablelands were more diverse than on the slopes and plains where C. marksi and C. austropalpalis dominated. The temporal and spatial variation in abundance, diversity and evenness of species reported in this diverse region of Australia provides additional insight into Culicoides as pests and disease vectors and may contribute to future modelling studies.

Application of an embryonated chicken egg model to assess the vector competence of Australian Culicoides midges for bluetongue viruses.

Culicoides biting midges (Diptera: Ceratopogonidae) are vectors of a number of globally important arboviruses that affect livestock, including bluetongue virus (BTV), African horse sickness virus and the recently emerged Schmallenberg virus. In this study, a model using embryonated chicken eggs (ECEs) was utilized to undertake vector competence studies of Australian Culicoides spp. for 13 laboratory-adapted or wild-type virus strains of BTV. A total of 7393 Culicoides brevitarsis were reared from bovine dung, and 3364 Culicoides were induced to feed from ECEs infected with different strains of BTV. Of those, 911 (27%) survived the putative extrinsic incubation period of 9-12 days. In some trials, virus was also transmitted onward to uninfected ECEs, completing the transmission cycle. This model does not rely on the use of colonized midges and has the capacity to assess the vector competence of field-collected insects with strains of virus that have not previously been passaged in laboratory culture systems. There is also potential for this model to be used in investigations of the competence of Culicoides spp. for other arboviruses.

Genotyping of whole genome amplified reduced representation libraries reveals a cryptic population of Culicoides brevitarsis in the Northern Territory, Australia.

BackgroundThe advent of genotyping by Next Generation Sequencing has enabled rapid discovery of thousands of single nucleotide polymorphism (SNP) markers and high throughput genotyping of large populations at an affordable cost. Genotyping by sequencing (GBS), a reduced representation library sequencing method, allows highly multiplexed sequencing of genomic subsets. This method has limitations for small organisms with low amounts of genomic DNA, such as the bluetongue virus (BTV) vectors, Culicoides midges.ResultsThis study employed the GBS method to isolate SNP markers de novo from whole genome amplified Culicoides brevitarsis genomic DNA. The individuals were collected from regions representing two different Australian patterns of BTV strain distribution: the Northern Territory (NT) and the east coast.We isolated 8145 SNPs using GBS. Phylogenetic analysis conducted using the filtered 3263 SNPs revealed the presence of a distinct C. brevitarsis sub-population in the NT and this was confirmed by analysis of mitochondrial DNA. Two loci showed a very strong signal for selection and were unique to the NT population. Bayesian analysis with STRUCTURE indicated a possible two-population cluster.ConclusionsThe results suggest that genotyping vectors with high density markers in combination with biological and environmental data is useful. However, more extensive sampling over a wider spatial and temporal range is needed. The presence of sub-structure in populations and loci under natural selection indicates the need for further investigation of the role of vectors in shaping the two Australian systems of BTV transmission. The described workflow is transferable to genotyping of small, non-model organisms, including arthropod vectors of pathogens of economic and medical importance.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-3124-1) contains supplementary material, which is available to authorized users.

Population Genetic Structure and Potential Incursion Pathways of the Bluetongue Virus Vector Culicoides brevitarsis (Diptera: Ceratopogonidae) in Australia.

Culicoides brevitarsis is a vector of the bluetongue virus (BTV), which infects sheep and cattle. It is an invasive species in Australia with an assumed Asian/South East Asian origin. Using one mitochondrial marker (i.e., part of the cytochrome oxidase subunit I gene) and six nuclear markers, we inferred population genetic structure and possible incursion pathways for Australian C. brevitarsis. Nine mitochondrial haplotypes, with low nucleotide sequence diversity (0.0–0.7%) among these, were identified in a sample of 70 individuals from seven sites. Both sets of markers revealed a homogeneous population structure, albeit with evidence of isolation by distance and two genetically distinct clusters distributed along a north-to-south cline. No evidence of a cryptic species complex was found. The geographical distribution of the mitochondrial haplotypes is consistent with at least two incursion pathways into Australia since the arrival of suitable livestock hosts. By contrast, 15 mitochondrial haplotypes, with up to four times greater nucleotide sequence diversity (0.0–2.9%) among these, were identified in a sample of 16 individuals of the endemic C. marksi (sampled from a site in South Australia and another in New South Wales). A phylogenetic tree inferred using the mitochondrial marker revealed that the Australian and Japanese samples of C. brevitarsis are as evolutionarily different from one another as some of the other Australian species (e.g., C. marksi, C. henryi, C. pallidothorax) are. The phylogenetic tree placed four of the species endemic to Australia (C. pallidothorax, C. bundyensis, C. marksi, C. henryi) in a clade, with a fifth such species (C. bunrooensis) sharing a common ancestor with that clade and a clade comprising two Japanese species (C. verbosus, C. kibunensis).

Assessment of population genetic structure in the arbovirus vector midge, Culicoides brevitarsis (Diptera: Ceratopogonidae), using multi-locus DNA microsatellites.

Bluetongue virus (BTV) is a major pathogen of ruminants that is transmitted by biting midges (Culicoides spp.). Australian BTV serotypes have origins in Asia and are distributed across the continent into two distinct episystems, one in the north and another in the east. Culicoides brevitarsis is the major vector of BTV in Australia and is distributed across the entire geographic range of the virus. Here, we describe the isolation and use of DNA microsatellites and gauge their ability to determine population genetic connectivity of C. brevitarsis within Australia and with countries to the north. Eleven DNA microsatellite markers were isolated using a novel genomic enrichment method and identified as useful for genetic analyses of sampled populations in Australia, northern Papua New Guinea (PNG) and Timor-Leste. Significant (P < 0.05) population genetic subdivision was observed between all paired regions, though the highest levels of genetic sub-division involved pair-wise tests with PNG (PNG vs. Australia (FST = 0.120) and PNG vs. Timor-Leste (FST = 0.095)). Analysis of multi-locus allelic distributions using STRUCTURE identified a most probable two-cluster population model, which separated PNG specimens from a cluster containing specimens from Timor-Leste and Australia. The source of incursions of this species in Australia is more likely to be Timor-Leste than PNG. Future incursions of BTV positive C. brevitarsis into Australia may be genetically identified to their source populations using these microsatellite loci. The vector’s panmictic genetic structure within Australia cannot explain the differential geographic distribution of BTV serotypes.Electronic supplementary materialThe online version of this article (doi:10.1186/s13567-015-0250-8) contains supplementary material, which is available to authorized users.

Factors affecting the distribution of Culicoides spp. (Diptera: Ceratopogonidae) vectors of bluetongue virus (BTV) in Australia

AbstractThis study examined environmental and geographical factors affecting the distribution of the bluetongue virus vectors Culicoides brevitarsis Kieffer, C. actoni Smith, C. fulvus Sen and Das Gupta and C. wadai Kitaoka in Australia using graphical analysis. Calculations and mapping were carried out in the R programming environment using freely available data. Average low temperatures of 13.5°C in June and in September were estimated as thresholds and expressed as contours at which C. brevitarsis activity ceases and then recommences during and after winter, respectively. The June threshold also designated areas where populations would be unable to survive the winter. There was substantial variability in the contours between years, around which the activity of C. brevitarsis would be correspondingly dynamic. Culicoides wadai, C. actoni and C. fulvus appeared to be less tolerant of low temperatures. A high temperature limit was proposed at a maximum 35°C during summer. Culicoides brevitarsis was found in areas above and below this temperature, while C. actoni, C. fulvus and C. wadai occurred mainly in coastal environments at maximum temperatures of less than 35°C. Possible effects of global warming were considered with 1°C or 2°C rises in temperature. Changes to low temperature thresholds could expose greater areas of southern Australia to vector activity, while temperature rises in the north could increase the size of areas in which temperatures are lethal to the vectors. Rainfall had no apparent effect on C. brevitarsis during the northern wet and dry seasons. Distributions of C. brevitarsis and cattle overlapped until both ended with the climatic change to desert, which formed a physical barrier preventing C. brevitarsis movement to the south. Temperature restricted associations between C. brevitarsis and sheep. The other Culicoides spp. were found outside major cattle and sheep production areas. Apart from seasonal and dynamic activity around the contours, cattle and sheep in areas below a June average temperature of 13.5°C should remain vector free at current climatic temperatures.

Evaluation of Metarhizium anisopliae for the control of Culicoides brevitarsis Kieffer (Diptera: Ceratopogonidae), the principal vector of bluetongue virus in Australia.

Four isolates of the entomopathogenic fungus Metarhizium anisopliae were tested for their potential to control the biting midge Culicoides brevitarsis, the principal vector of bluetongue virus in Australia. Adult C. brevitarsis died three to eight days after walking on paper substrate treated with 0.7 g/m(2) conidia of any of the isolates, indicating that M. anisopliae has potential as a surface treatment or topical application control strategy. Incorporation of the fungus into freshly excreted cattle dung at rates of between 0.25 and 1 g conidia/kg reduced the emergence of adult midges by up to 98.5% compared to untreated dung indicating that M. anisopliae has the potential to control C. brevitarsis larvae in cattle dung. Three of the isolates produced similar mortality rates on adult and immature C. brevitarsis while the fourth isolate produced lower, but still significant, mortality rates on adult and immature stages.

Molecular Identification of Field-CollectedCulicoidesLarvae in the Southern Part of Japan

Although Culicoides biting midges act as a vector of important human and domestic animal diseases, their ecology is poorly understood. The lack of proper identification systems of Culicoides larvae is one of the main obstacles to progress in research. Based on mitochondrial sequences of 19 Japanese Culicoides species, we designed a universal primer set to amplify the partial sequence of the mitochondrial cytochrome c oxidase I (cox 1). The polymerase chain reaction product amplified from extracted DNA of Culicoides larvae using the primer set was directly sequenced, and species identification based on the variation at cox1 was conducted. Using the molecular identification system, we sorted 243 specimens of field-collected larvae from the southern part of Japan into 10 species including Culicoides arakawae (Arakawa), Culicoides oxystoma Kieffer, and Culicoides brevitarsis Kieffer, which are regarded as vectors of important livestock animal diseases. Eight species of Culicoides larvae, including C. arakawae and C. oxystoma, were recovered from active paddy fields and an abandoned paddy field. The result suggests that paddy fields contribute to breeding a variety of Culicoides species and maintenance and spread of Culicoides-borne pathogens. In contrast, larvae of C. brevitarsis were collected from cattle dung in pastures. The molecular identification system described herein using nucleotide sequences successfully achieved larval identification and will be useful for a better understanding of larval habitats of Culicoides biting midges.

Malakal virus from Africa and Kimberley virus from Australia are geographic variants of a widely distributed ephemerovirus

Kimberley virus (KIMV) is an arthropod-borne rhabdovirus that was isolated in 1973 and on several subsequent occasions from healthy cattle, mosquitoes (Culex annulirostris) and biting midges (Culicoides brevitarsis) in Australia. Malakal virus (MALV) is an antigenically related rhabdovirus isolated in 1963 from mosquitoes (Mansonia uniformis) in Sudan. We report here the complete genome sequences of KIMV (15442 nt) and MALV (15444 nt). The genomes have a similar organisation (3′-l-N-P-M-G-GNS-α1-α2-β-γ-L-t-5′) to that of bovine ephemeral fever virus (BEFV). High levels of amino acid identity in each gene, similar gene expression profiles, clustering in phylogenetic analyses of the N, P, G and L proteins, and strong cross-neutralisation indicate that KIMV and MALV are geographic variants of the same ephemerovirus that, like BEFV, occurs in Africa, Asia and Australia.

Tibrogargan and Coastal Plains rhabdoviruses: genomic characterization, evolution of novel genes and seroprevalence in Australian livestock

Tibrogargan virus (TIBV) and Coastal Plains virus (CPV) were isolated from cattle in Australia and TIBV has also been isolated from the biting midge Culicoides brevitarsis. Complete genomic sequencing revealed that the viruses share a novel genome structure within the family Rhabdoviridae, each virus containing two additional putative genes between the matrix protein (M) and glycoprotein (G) genes and one between the G and viral RNA polymerase (L) genes. The predicted novel protein products are highly diverged at the sequence level but demonstrate clear conservation of secondary structure elements, suggesting conservation of biological functions. Phylogenetic analyses showed that TIBV and CPV form an independent group within the 'dimarhabdovirus supergroup'. Although no disease has been observed in association with these viruses, antibodies were detected at high prevalence in cattle and buffalo in northern Australia, indicating the need for disease monitoring and further study of this distinctive group of viruses.

Detection of Culicoides brevitarsis Activity in Kyushu

Culicoides brevitarsis transmits important ruminant arboviruses, such as Akabane, Aino and bluetongue viruses. The presence of this species has so far been recognized primarily in Okinawa, the southernmost prefecture of Japan. In entomological surveys in 2008 and 2009, C. brevitarsis was collected at 8 sites throughout Nagasaki, Kumamoto and Kagoshima Prefectures. The collection sites are all located near pastures, where the larvae of C. brevitarsis can grow in cattle dung left in the field. C. brevitarsis was confirmed at the same sites in two consecutive years, suggesting that it overwinters in Kyushu. Given the risk of arbovirus transmission, the ecology of C. brevitarsis in Japan, such as its distribution range, seasonal abundance and larval breeding sites, should be investigated in more detail.

Attraction of Culicoides brevitarsis Kieffer (Diptera: Ceratopogonidae) and Culex annulirostris Skuse (Diptera: Culicidae) to simulated visual and chemical stimuli from cattle

Abstract Different host‐seeking responses to cattle by Culicoides brevitarsis and Culex annulirostris were found using two‐dimensional cattle‐shapes and simulated stimuli. Culicoides brevitarsis was attracted to the respiratory chemicals CO2 and CO2 + octenol but not to octenol alone. It was attracted to cattle‐shape when CO2 + octenol was also present and when the shape was enhanced with visible and infrared light. Culex annulirostris was attracted to each chemical treatment but not to any visual stimuli. Orientation of the host, possibly in relation to wind direction, may also be important but requires further consideration. The detection of behavioural differences between the species was dependent on the positioning of attractants and traps in relation to the host image. Responses by C. brevitarsis to CO2 + octenol and the basic shape were only recorded in sticky traps. Contact with the shape was recorded initially on the shape head but preference was shown later to be for the ridge‐line of the back. The response by Cx. annulirostris to CO2 + octenol was only recorded in light traps placed centrally and above the shape. It is proposed that the initial location of hosts by C. brevitarsis is by visual stimuli. Attraction to CO2 + octenol is secondary and probably only occurs close to the host. The chemicals help the midge to recognise and come to the potential host where landing is induced visually near the interface between the backline of the host and the background. The primary response by Cx. annulirostris is to CO2 and octenol although these did not appear to bring this insect on to the host. Covers could be used to protect cattle from C. brevitarsis (but not Cx. annulirostris) by blocking the visual stimuli.

Comparative descriptions of the pupae of five species of the &lt;i&gt;Culicoides imicola complex&lt;/i&gt; (Diptera, Ceratopogonidae) from South Africa

The viruses causing the economically important livestock diseases of African horse sickness (AHS) and bluetongue (BT) are transmitted by biting midges of the genus Culicoides (Diptera, Ceratopogonidae). In the Old World the most important vectors of these diseases are Culicoides imicola Kieffer, 1913, Culicoides brevitarsis Kieffer, 1917 and Culicoides bolitinos Meiswinkel, 1989. All three of these vectors belong to the Imicola complex of the subgenus Avaritia Fox, 1955. This species complex now comprises 12 sibling species; ten occur in sub-Saharan Africa and are difficult to identify (based mostly on subtle variations in the wing latterns) and so additional methods of reliable identification are needed. The pupal exuviae of the five commonest sibling species (C. imicola, C. bolitinos, Culicoides loxodontis Meiswinkel, 1992, Culicoides tuttifrutti Meiswinkel, Cornet & Dyce, 2003 and Culicoides sp. # 107) harvested from a variety of large herbivore dung types and from decaying fruits, are described and illustrated in detail. It is shown that they can be differentiated clearly on a number of morphological characters and, furthermore, are separable into two distinct groups based (principally) on the shape of the respiratory organ. A key for identifying and differentiating these five pupae is provided. Also, the pupa of the Oriental-Australasian C. brevitarsis was compared with its allopatric sister taxon, C. bolitinos. Because they share a common larval habitat (cattle and buffalo dung) and are almost inseparable in the adult phenotype, the question of their possible synonymy is raised. However, their respective pupae could not be differentiated on gross morphology and so it is argued that this unresolved problem requires a molecular solution.

Light trapping of biting midges Culicoides spp. (Diptera: Ceratopogonidae) with green light‐emitting diodes

Abstract A study of responses by Culicoides spp. to light traps with light‐emitting diodes (LEDs) confirmed that the livestock virus vector, Culicoides brevitarsis Kieffer, was preferentially attracted to green light. Four species shown previously to respond to blue light exhibited significantly higher responses to ultraviolet (UV) light. Field trials comparing green LEDs with incandescent lights in New South Wales, Northern Territory and East Timor confirmed the superiority of green LEDs for catching C. brevitarsis. The green LED traps also had a significant advantage over incandescent traps for a wide range of Culicoides species. These included: species whose ultimate preference was for UV, most species that are proven or potential vectors of viruses affecting Australian livestock and native animals and the main species affecting humans in northern Australia. Use of green LEDs has been adopted for trapping C. brevitarsis, especially in its marginal and low‐density areas, and for detecting incursions of new Culicoides spp. into Australia. Use could be possible for species in other insect Orders.

Effects of altitude, distance and waves of movement on the dispersal in Australia of the arbovirus vector, Culicoides brevitarsis Kieffer (Diptera: Ceratopogonidae)

The dispersal of the biting midge and arbovirus vector Culicoides brevitarsis in the Bellinger, Macleay and Hastings river valleys and up the escarpment of the great dividing range (GDR) of mid-northern coastal New South Wales, Australia, from 1995 to 2003 was studied. The midge moved up these valleys from the endemic coastal plain in at least two waves between October and May, and both waves were modelled. Dispersal time can be explained by direct distance from the coast and the altitude of the sites. Dispersal times due to distance were similar at 18.2 ± 2.2 (S.D.) and 15.9 ± 2.6 weeks per 100 km for first- and second-occurrences at fixed altitude. Time of the first wave was extended 0.48 ± 0.22 weeks for every 100-m rise in altitude and the second by 1.14 ± 0.24 weeks for every 100-m rise for a set distance. Although C. brevitarsis can move up the escarpment of the GDR (and possibly transmit virus), vector dispersal, survival and establishment at and beyond the top of the range are limited. A third model showed that previously described slower movement of C. brevitarsis up the more-southerly Hunter valley relative to movements down the coastal plain also was related to increasing altitude.

Response of Culicoides spp. (Diptera: Ceratopogonidae) to light‐emitting diodes

Abstract Light traps with incandescent globes are used in a national monitoring program to detect the presence of Culicoides spp. responsible for the transmission of viruses to livestock and native animals. Recent events have suggested that the efficiency of these traps should be reconsidered and possibly improved. Subsequently, the response of eight species of Culicoides to light‐emitting diodes (LEDs) was determined at two locations in New South Wales. Culicoides austropalpalis Lee &amp; Reye, C. bunrooiensis Lee &amp; Reye and C. marksi Lee &amp; Reye were attracted to blue light. Responses to blue and green light could not be separated for C. bundyensis Lee &amp; Reye, C. dycei Lee &amp; Reye, C. nattiensis Lee &amp; Reye and C. victoriae Macfie. Culicoides brevitarsis Kieffer was significantly attracted to green light. This species is the major vector of Akabane and bluetongue viruses in Australia. These responses were all significantly greater than the responses to the incandescent lights currently used in the light traps. The response to red light was less than the response to incandescent light for all species. Catches of C. brevitarsis were also related to the intensity of the green LEDs. These were more effective than the currently used incandescent globes at intensities between 46% and 142% of the incandescent intensity.

Models for the dispersal in Australia of the arbovirus vector, Culicoides brevitarsis Kieffer (Diptera: Ceratopogonidae)

Culicoides brevitarsis is the main biting midge responsible for the transmission of bluetongue and Akabane viruses to livestock in Australia. Models are given for its dispersal after winter from endemic areas at the southern limit of its distribution in New South Wales (NSW); the models might also be applicable elsewhere. Model 1 shows that dispersal can be explained by distance from a key point just outside the endemic area in mid-northern/northern coastal NSW. The model provides probability data for times of first occurrence at sites within regions down the southern coastal plain or up the Hunter Valley towards (but rarely reaching) the western slopes and tablelands. Model 2 shows that the movement depends on temperature and wind speed from northerly and easterly directions. Preliminary data also are given to suggest a relationship between density in the endemic area and the maximum distance that C. brevitarsis can travel in a given year. The models can be linked to other information which in combination can provide probabilities for winter survival outside the endemic area, times of occurrence at sites where it cannot survive winter and times when activity ceases naturally at these sites at the end of the season. This information can be used to predict the potential for virus transmission and indicate zones of seasonal freedom from both vector and virus for the export of livestock.

Moon phase and other factors affecting light-trap catches of Culicoides brevitarsis Kieffer (Diptera: Ceratopogonidae)

Light-trap catches of Culicoides brevitarsis were affected by the phase of the moon with least being caught at the full moon. Seasonal catches were also influenced by temperature and windspeed. Conversely, changes in moonlight overnight at the full moon had no obvious effect on the species capture in light traps. Nightly catches were mainly influenced by temperature when the effect of windspeed was negated. Differences related to moon phase were most likely the result of alterations to the effective limit of attraction of traps induced by competition with moonlight. This and the other factors would make it difficult to interpret and compare numbers of C. brevitarsis caught in light traps at different times and locations.

Factors affecting numbers of Culicoides in truck traps in coastal Queensland.

Truck trap collections of Ceratopogonidae were made over a period of 27 months (November 1973-February 1976) at Tingalpa Creek, in southeast Queensland, Australia. Six collections were made on each of 95 days, giving 570 observations and a total of 29,378 Culicoides. Two collections were made before, one at, and three after sunset. Separate analyses were made of the catches of thirteen entities: male and female C. austropalpalis, C. brevitarsis, C. marksi, C. marmoratus and C. victoriae, female C. henryi and C. longior, and total C. bundyensis. Catches were dominated by C. brevitarsis (35.2%) and C. marmoratus (32.3%) and, with C. victoriae, were taken on almost every collecting day over all seasons. Sex ratios (M:F) varied from 0:100 for C. longior to 130:100 for C. marksi. Collections of all entities, except female C. henryi, were greatest (50-70% of the daily catch) at sunset. In winter there was substantial activity in the hour before sunset. Time of day was the most important variable, accounting for 15-45% of the observed variation. Between-day differences were significant for all except C. austropalpalis, C. victoriae and male C. marksi. Culicoides brevitarsis, C. bundyensis and C. longior had highly significant annual cycles, C. victoriae and female C. austropalpalis had significant lunar cycles, and C. longior had a significant tidal cycle. Logarithms of catches of female C. austropalpalis, C. brevitarsis, C. henryi, C. marmoratus, and female and male C. victoriae were inversely related to linear wind speed. Log catches of female C. austropalpalis, C. brevitarsis, C. marmoratus and C. victoriae, and male C. marksi and C. victoriae were positively related to temperature (quadratic).