Interactions between dung beetles (Coleoptera: Scarabaeidae) and the arbovirus vector Culicoides brevitarsis Kieffer (Diptera: Ceratopogonidae)

Abstract  The potential for dung beetles to reduce populations of the biting midge and arbovirus vector Culicoides brevitarsis in bovine dung was studied in the Hunter Valley, New South Wales (NSW) between 1999 and 2003 using natural populations of insects. Preliminary work to develop experimental procedures showed that: a few C. brevitarsis could survive in buried dung; dung beetles and C. brevitarsis coming to dung were unaffected by a background of shade-cloth used experimentally to prevent dung burial; the most abundant dung beetle, Onthophagus gazella L. and C. brevitarsis oviposition occurred concurrently in the first 2 d after dung deposition, and the potential for interaction between dung beetles and C. brevitarsis was greatest in open pasture adjacent to trees where cattle congregate at night. Laboratory experiments on dung burial showed that C. brevitarsis numbers decreased as numbers of dung beetles increased or as the dry weight of dung decreased due to burial. This was seldom reflected in the field where, although significant burial occurred experimentally in 9 of 20 trials over 3 years, a significant decline in C. brevitarsis numbers attributable to burial only occurred once. C. brevitarsis numbers in the field were lower in unburied dung in 70% of trials. Differences were significant twice and were considered the result of dung disturbance. In the laboratory, decreasing numbers of C. brevitarsis were related to three characteristics of disturbance: the flattening, spreading and reduction in wet weight of the dung. Evidence of C. brevitarsis activity throughout coastal NSW suggests that, while C. brevitarsis numbers may be modified by dung beetles, the interaction is insufficient to prevent their increase, spread and ability to transmit viruses to livestock.     

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.     

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/m² 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.     

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).     

First Record of Culicoides oxystoma Kieffer and Diversity of Species within the Schultzei Group of Culicoides Latreille (Diptera: Ceratopogonidae) Biting Midges in Senegal

The Schultzei group of Culicoides Latreille (Diptera: Ceratopogonidae) is distributed throughout Africa to northern Asia and Australasia and includes several potential vector species of livestock pathogens. The taxonomy of the species belonging to this species group is confounded by the wide geographical distribution and morphological variation exhibited by many species. In this work, morphological and molecular approaches were combined to assess the taxonomic validity of the species and morphological variants of the Schultzei group found in Senegal by comparing their genetic diversity with that of specimens from other geographical regions. The species list for Senegal was updated with four species: Culicoides kingi, C. oxystoma, C. enderleini and C. nevilli being recorded. This is the first record of C. oxystoma from Africa south of Sahara, and its genetic relationship with samples from Israel, Japan and Australia is presented. This work provides a basis for ecological studies of the seasonal and spatial dynamics of species of this species group that will contribute to better understanding of the epidemiology of the viruses they transmit.     

First report of Culicoides boyi (Diptera: Ceratopogonidae) in France

Culicoides boyi Nielsen, Kristensen & Pape 2015 (Diptera: Ceratopogonidae), described in Denmark in 2015, is reported in France. This species is closely related to Culicoides pulicaris (Linnaeus 1758) and can only be distinguished from this species by a subtle variation in spot wing pattern and by calculation of maxillary palpal ratio.     

Description of the Pupa of Culicoides crucifer Clastrier (Diptera: Ceratopogonidae)

The pupa of Culicoides crucifer Clastrier is described, illustrated and photomicrographed by using binocular microscope and phase-contrast microscopy from material collected in an artificial container in Manaus, Brazil. The pupa shows features typical of pupae occurring in calm and clean waters, and it is compared with its similar congeners of the subgenus Haematomyiidium, Culicoides annuliductus Wirth and Culicoides debilipalpis Lutz.     

山西永济毛蠓一新种的描述(双翅目:蠓科)

2003年8月中旬在晋陕接壤地带进行医学昆虫调查时,在山西永济境内普救寺花园内采集到若干蠓类,经分类研究,发现1毛蠓新种,命名为普寺毛蠓Dasyhelea pusi Yu and Yan sp.nov.,本文描述了该新种两性成虫的形态特征.模式标本收藏于医学昆虫标本馆.     

Effects of seawater components on immature Culicoides molestus (Skuse) (Diptera: Ceratopogonidae)

Abstract Following analysis of beach sites and an indication that seawater components might influence larval occurrence, we studied the impact of increasing salinity and seawater concentration on survival of fourth-instar larvae of the canal biting midge, Culicoides molestus . While NaCl had little effect on immature survival, increasing the concentration of seawater increased mortality prior to the adult stage. Seawater at three and four times the normal concentration killed all immatures. Artificial elevation of seawater concentration in the sandy substrate preferred by larvae, therefore, has the potential to reduce immature midge survival. Diet also affected survival, with higher mortality of immatures that were fed fish-food flakes compared with those that were fed live nematodes.