Laboratory Rearing of Culicoides stellifer (Diptera: Ceratopogonidae), a Suspected Vector of Orbiviruses in the United States

Epizootic hemorrhagic disease virus oral infection affects midge reproduction and is vertically transmitted to offspring in Culicoides sonorensis

Epizootic hemorrhagic disease virus (EHDV: Reoviridae: Orbivirus) is a Culicoides-borne pathogen that affects a variety of ruminants, causing significant economic losses and/or ecological impacts in animal agriculture/wildlife populations worldwide. In this study, we examined the effect of EHDV serotype-2 oral infection on the survival and reproduction of Culicoides sonorensis Wirth and Jones (a confirmed vector of EHDV in North America), and the potential vertical transmission of EHDV-2 (from infected female to its offspring) in this midge species. Culicoides sonorensis females were fed on defibrinated bovine blood mixed with EHDV-2 (5.5 log10 PFU/ml) or without EHDV-2 (control). Adult survival/longevity, oviposition rates, number of eggs deposited, egg hatch rates (fertility), larval survival, larval stage duration, eclosion rates, and sex-ratios of the progeny were recorded and compared between the two groups. In addition, the progeny (eggs and F1 generation adults) of EHDV-2 fed females were processed for viral detection through RT-qPCR and plaque assays. Survival/longevity of the blood-fed adults, oviposition rates, number of eggs deposited, larval stage duration, eclosion rates, and sex-ratios were not significantly different between the two groups. However, egg hatch rates were significantly lower in the EHDV-2 fed group (35.8 ± 5.2%) than the control group (74.5 ± 6.8%), but larval survival rates were higher in the EHDV-2 fed group (59.8 ± 4.9%) compared to the control group (34.1 ± 6.5%). EHDV-2 (Ct < 35) was detected in the eggs (3.4%, 1/29 females tested, Ct = 22.1 [4.9 log10 PFUe/ml]) and F1 adult progeny (1.7%, 1/58 adults tested, Ct = 23.5 [4.5 log10 PFUe/ml]) of the orally exposed females through RT-qPCR as well as through plaque assays. Our findings suggest that EHDV-2 infection has no major impact on C. sonorensis survival/longevity or oviposition but has a significant negative effect on midge fecundity/fertility. Our study also provides evidence for the vertical transmission of EHDV-2 from an infected adult female to its offspring in C. sonorensis. However, salivary transmission of EHDV-2 from the vertically infected progeny and its significance in the epidemiology of hemorrhagic disease are currently unknown and remain to be examined in further studies. Overall, these findings collectively indicate that Orbivirus infection can negatively affect vector reproduction, and that vertical transmission is a probable mechanism of overwintering of EHDV in North America.

First record of bacterial communities within defecated contents and gut of post-defecated females of Culicoides peregrinus Kieffer and Culicoides oxystoma Kieffer (Diptera: Ceratopogonidae), vectors of bluetongue virus

Defecation is one of the posterior-station transmission routes for pathogens in haematophagous insects. Culicoides peregrinus Kieffer and Culicoides oxystoma Kieffer (Diptera: Ceratopogonidae) are the proven vectors of many arboviruses, most importantly bluetongue virus, protozoa, and filarial nematodes of livestock. Duration of blood feeding and defecation vary according to species. Culicoides females take blood from their hosts to acquire additional protein to develop their eggs. This study investigates the bacterial communities in defecated contents and gut of the field-collected post-defecated females of C. peregrinus and C. oxystoma. To observe the defecation period and pathogenic bacteria in their defecated contents, engorged females of both species were investigated. The females were transferred to the glass vials containing moistened cotton beds at the bottom and kept in an environmental test chamber. The females defecated within 48 h of post-blood meal intake. The defecated contents discharged by C. peregrinus contained the following bacterial species: Bacillus cereus, Bacillus flexus, Enterococcus faecium, Proteus vulgaris, and C. oxystoma: B. cereus, E. faecium, and Alcaligenes faecalis. Bacillus cereus, B. flexus, Paenibacillus sp., E. faecium, A. faecalis, and Brevundimonas sp. were obtained from the gut of post-defecated females of C. peregrinus, and B. cereus, Lysinibacillus sp., and Paenibacillus sp. were identified from the gut contents of post-defecated females of C. oxystoma. Within the defecated contents, the following pathogenic bacteria, B. cereus, P. vulgaris, and A. faecalis, were detected, which raises the chances of zoonotic posterior transmission to their hosts that should be investigated.

Unraveling the relationships between midge abundance and incidence, microbial communities, and soil and water properties in a protected natural tallgrass prairie

BACKGROUND

Biting midges (Culicoides spp.) are small blood-feeding flies (Diptera: Ceratopogonidae) that transmit numerous pathogens that impact animal and human health. The larvae of several Culicoides spp., including vectors, are often found in organically enriched, moist soil habitats. However, the influence of biotic (e.g., cohabiting fauna, potential prey taxa) and abiotic factors (e.g., soil or water properties, time) on abundance and incidence of larval Culicoides in natural habitats is not well understood. This study evaluated the relationships between bacterial and protistan communities, soil and water physicochemical properties, and the abundance and incidence of Culicoides species in larval habitats at the Konza Prairie Biological Station in Kansas.

METHODS

Soil and water samples were collected monthly from March 2021 to February 2022 from four midge larval habitat sites, including three grazed (low-production cattle-grazed (LPCG), high-production cattle-grazed (HPCG), and bison-grazed sites) and one formally ungrazed (i.e., no managed large mammals) site. Midge incidence and abundance were evaluated using emergence assays, which assessed the number of adults emerging from collected soil samples, and bacterial and protistan communities in these samples were characterized through amplicon sequencing of the 16S and 18S rRNA genes. Physicochemical properties of water and soil were also analyzed.

RESULTS

Irrespective of site, the highest midge abundance was reported in warmer months between March and September, except June. Moreover, the greatest midge abundance, incidence, and prevalence occurred at the HPCG and bison-grazed sites, which had a persistent water source. Specific lineages of bacterial and protistan communities, soil texture, organic matter, and total dissolved solids in water samples were directly associated with the abundance of Culicoides spp. that emerged from soil samples.

CONCLUSIONS

Both biotic (bacterial and protistan communities, presence of host animals), and abiotic (soil and water properties, season) factors affected the abundance and incidence of Culicoides spp. in natural habitats. The results presented in this study expand our understanding of the ecological and environmental factors influencing larval ecology of biting midges in natural developmental substrates. These insights have important implications for identifying potential developmental sites, which can be used for targeted management of Culicoides.

Elucidating the life history parameters of Culicoides oxystoma (Diptera: Ceratopogonidae) under varied substrate compositions and temperatures

A comprehensive study was conducted on the life history parameters of an important vector Culicoides oxystoma Kieffer (Diptera: Ceratopogonidae), to standardize potential rearing procedures. Data on life history traits and rearing conditions are crucial for establishing laboratory colony and conducting vector competence-based studies utilizing specimens with a known rearing history. Six different substrate compositions were used to rear the larvae: S1: habitat mud containing cattle manure + nutrient broth + yeast, S2: yeast, S3: habitat mud containing cattle manure + nutrient broth, S4: nutrient broth, S5: sterile (habitat mud consisting cattle manure + nutrient broth + yeast) and S6: tap water. Gravid females preferred ovipositing on beds moistened with tap water compared to distilled water. Egg hatching recorded minimal (3%) in the sterile substrate (S5), hinting at the role of live microbial load. Progression of larval instars got disrupted at 1st instars in S5 and S6. Larval survival and adult emergence were the highest in S1 and the lowest in S4, indicating that S1 is highly effective in the rearing of this species. The life cycle parameters and duration between transitional stages were evaluated at 15 °C, 20 °C, 26 °C, 30 °C, and 35 °C using rearing substrate S1. The highest larval survival (>70%) and adult emergence (69%) were achieved at 26 °C. The duration from egg to adult was 16 to 20 d at 35 °C, 18 to 24 d at 26 °C, but up to 36 d at 15 °C. Elucidating the effective rearing conditionalities of this important vector species will be helpful to study the transmission cycles of pathogens.

Isolation and comparative analysis of culturable bacterial communities associated with life stages, breeding and rearing substrates of Culicoides oxystoma Kieffer (Diptera: Ceratopogonidae) vector of bluetongue virus

Culicoides oxystoma Kieffer (Diptera: Ceratopogonidae) has been vectoring several arboviruses, protozoa and nematodes, leading to mortality and morbidity of livestock and wild ruminants in the tropics and subtropics. Insight into the bacterial communities associated with the vector species must be worked out. This work tries to inventorize the bacterial communities associated with this important vector species. Acquisition of gut microbiota may be the parental origin, while some are obtained through feeding during larval stages. Culicoides oxystoma possesses semi-aquatic life cycle strategies for egg-laying and larval survival. The bacteria associated with C. oxystoma were compared throughout (i) life stages: egg, larval instars, pupa, adult: male and female obtained from laboratory colony; (ii) field-collected adult: male and age-graded females; and (iii) natural breeding substrate and artificial rearing substrate. The culture-dependent bacteria were identified by Sanger sequencing of 16S rRNA, and haemolytic bacteria were screened on blood agar. Results show that Firmicutes and Proteobacteria are the predominant Phyla, of which Bacillus spp. was the most abundant across the life stages. Across the life history, Bacillus cereus, Bacillus pumilus, Bacillus tropicus, Lysinibacillus sp. and Paenibacillus sp. were retrieved routinely. Bacillus cereus and Alcaligenes faecalis were detected in the lab-reared specimens and shared between the natural breeding site and rearing medium. From the adults trapped across two locations, B. cereus, Bacillus flexus, A. faecalis, Enterococcus faecium and Pseudomonas sp. were isolated. The bacterial species associated with this vector may influence various physiological traits, such as vectorial capacity, digestion and larval development, which need further investigation.

In vitro biochemical characterization and identification of hemolytic bacteria associated with life history of Culicoides peregrinus (Diptera: Ceratopogonidae), a vector of bluetongue virus

Gut bacterial communities in insects provide several beneficial roles like nutrition, digestion, fecundity, and survival of the host. The microbial communities of Culicoides spp. (Diptera: Ceratopogonidae) vary with parity, developmental stages, and environmental factors. Previous studies have revealed the presence of hemolytic bacteria in adult Culicoides peregrinus Kieffer (Diptera: Ceratopogonidae), an important vector of bluetongue virus (BTV). Our objectives were (i) to identify bacterial communities with hemolytic activities associated with all life stages and (ii) to compare between reared and field-collected adults including age graded females. Bacterial identification followed Sanger sequencing of 16S rRNA. In vitro biochemical characterizations including antibiotic sensitivity tests were also done. The majority of bacterial species were beta hemolytic with one, Alcaligenes faecalis, showing alpha hemolysis. Most bacterial species were observed in field-collected adults except Proteus spp. Throughout the life history of the vector, Bacillus cereus (CU6A, CU1E) and Paenibacillus sp. (CU9G) were detected indicating their possible role in blood digestion within the gut of this vector species. In vivo hemolytic activities of these culturable bacterial communities within this vector may be addressed in future. These hemolytic bacterial communities may be targeted to develop novel and effective strategies for vector control.

A Metagenomic Based Approach on Abundance and Diversity of Bacterial Communities Across the Life Stages of Culicoides peregrinus (Diptera: Ceratopogonidae) a Vector of Bluetongue Virus

During larval rearing of Culicoides peregrinus Kieffer (Diptera: Ceratopogonidae) it was obligatory to add a small quantity of mud from larval habitat to nutrient broth in culture plates. This initiated microbial growth in rearing plates which facilitated growth and development of immature. The primary aim was to enumerate gut microbial communities across the different life stages of C. peregrinus. Amplicon sequencing of the V3-V4 hypervariable region (16S rDNA) was done on Illumina Miseq platform to detect gut bacterial communities at different life stages, while ITS regions (18S rRNA) were targeted for fungal communities of the 4th instar larvae. The major findings were: 1) Phylum Proteobacteria and Firmicutes were the most abundant throughout the life stages, along with the highest bacterial alpha diversity in the egg, 2) bacterial compositions were similar to laboratory reared and field collected adults, and 3) abundant fungal phyla associated with the larval gut were Ascomycota and Basidiomycota. Furthermore, analyses of the gut microbiome with METAGENassist might be indicative of their likely function in the natural habitat. Abundant gut-associated bacteria and/or fungal genera detected in the present study could be used as dietary supplements to establish laboratory colonies for further vectorial research. While, individual roles of the bacteria or fungi in paratransgenesis are warned for their possible utilization to frame the management strategy in upcoming works.

Habitat type and host grazing regimen influence the soil microbial diversity and communities within potential biting midge larval habitats

BACKGROUND

Biting midges (Culicoides spp.) are important vectors of diverse microbes such as viruses, protozoa, and nematodes that cause diseases in wild and domestic animals. However, little is known about the role of microbial communities in midge larval habitat utilization in the wild. In this study, we characterized microbial communities (bacterial, protistan, fungal and metazoan) in soils from disturbed (bison and cattle grazed) and undisturbed (non-grazed) pond and spring potential midge larval habitats. We evaluated the influence of habitat and grazing disturbance and their interaction on microbial communities, diversity, presence of midges, and soil properties.

RESULTS

Bacterial, protistan, fungal and metazoan community compositions were significantly influenced by habitat and grazing type. Irrespective of habitat and grazing type, soil communities were dominated by phyla Acidobacteria, Actinobacteria, Bacteroidetes, Chloroflexi, Firmicutes, Proteobacteria (Bacteria); Apicomplexa, Cercozoa, Ciliophora, Ochrophyta (Protists); Chytridiomycota, Cryptomycota (Fungi) and Nematoda, Arthropoda (Metazoa). The relative abundance of Acidobacteria, Actinobacteria, Bacteroidetes, Chloroflexi, Firmicutes, Proteobacteria, Verrucomicrobia (Bacteria); Apicomplexa, Lobosa (Protists); Ascomycota, Blastomycotina, Cryptomycota (Fungi); and Platyhelminthes (Metazoa) were significantly affected by grazing type. Of note, midge prevalence was higher in grazed sites (67-100%) than non-grazed (25%). Presence of midges in the soil was negatively correlated with bacterial, protistan, fungal and metazoan beta diversities and metazoan species richness but positively correlated with protistan and fungal species richness. Moreover, total carbon (TC), nitrogen (TN) and organic matter (OM) were negatively correlated with the presence of midges and relative abundances of unclassified Solirubrobacterales (Bacteria) and Chlamydomonadales (Protists) but positively with Proteobacteria and unclassified Burkholderiales (Bacteria).

CONCLUSIONS

Habitat and grazing type shaped the soil bacterial, protistan, fungal and metazoan communities, their compositions and diversities, as well as presence of midges. Soil properties (TN, TC, OM) also influenced soil microbial communities, diversities and the presence of midges. Prevalence of midges mainly in grazed sites indicates that midges prefer to breed and shelter in a habitat with abundant hosts, probably due to greater accessibility of food (blood meals). These results provide a first glimpse into the microbial communities, soil properties and prevalence of midges in suspected midge larval habitats at a protected natural prairie site.

Field Comparison of Removed Substrate Sampling and Emergence Traps for Estimating Culicoides Orbivirus Vectors in Northern Florida

The larval ecology of Culicoides (Diptera: Ceratopogonidae) influences their spatial distributions and the pathogens they transmit. These features are of special concern for deer farmers in Florida where epizootic hemorrhagic disease virus (EHDV) is a major source of mortality in captive herds. Rarity of larval morphological expertise leads many researchers to study larval ecology by quantifying emergence, either with field emergence traps or removing substrate from the field for observation under laboratory conditions. We investigated the comparability of these methods in Florida seepages where two recently implicated EHDV vectors, Culicoides stellifer Coquillett and Culicoides venustus Hoffman, are common. We compared the abundance and composition of emerging Culicoides collected from emergence traps with removed substrate samples (soil plugs) at three seepages. Soil plugs were sampled adjacent to the emergence trap and from underneath the trap footprint, and then monitored under laboratory conditions for 11-13 wk to compare the methods and to assess the role of incubation period for removed substrate samples. Emergence traps and removed substrate sampling largely agreed on community compositions and trends within different seepages. However, comparatively large numbers of C. stellifer emerged later than expected and well into the incubation period with emergence still occurring after 13 wk (90 d). Removed substrate samples were more similar to emergence traps at shorter incubation times. The importance of time for the capture of Culicoides in removed substrate sampling was more pronounced than we anticipated and is important from both a methodological and biological perspective.

Host Bloodmeal Source Has No Significant Effect on the Fecundity and Subsequent Larval Development Traits of the Progeny in Culicoides furens Poey (Diptera: Ceratopogonidae)

Culicoides Latreille species (Diptera: Ceratopogonidae) are insects of significant medical and veterinary importance worldwide because their bites can cause major annoyance, allergic reactions, and/or pathogen transmission to vertebrates, including humans. In this study, we examined the effect of host bloodmeal source on the fecundity and subsequent larval development traits of the progeny of Culicoides furens Poey, a nuisance species in coastal Florida. Field-collected females were fed on two different classes of hosts: birds (chicken) or mammals (human). Fecundity outcomes of the females and larval developmental traits of the progeny were recorded and compared between the two groups. The percentage of females that developed eggs, percentage of gravid females that deposited eggs, number of eggs produced per female, number of eggs deposited per female, egg hatch rates, larval survival rates, time to pupation, pupal sex-ratios, and adult eclosion rates were not significantly different between the two groups. Our results demonstrate that the host bloodmeal source has no significant effect on the fecundity and subsequent larval developmental life-history traits of the progeny in C. furens. Previous studies reported C. furens to be a generalist feeder that shows no host preference for birds or mammals. Collectively, these findings suggest that C. furens is well adapted, not just behaviorally, but also physiologically to efficiently utilize blood meals from avian and mammalian hosts, a quality that offers a major evolutionary advantage to the success of this midge species as a generalist feeder.

Oviposition of Culicoides insignis (Diptera: Ceratopogonidae) under laboratory conditions with notes on the developmental life history traits of its immature stages

BACKGROUND

Culicoides insignis is a confirmed vector of bluetongue virus (BTV) throughout the American tropics and a possible vector of epizootic hemorrhagic disease virus (EHDV) in Florida. Despite its importance, fundamental information on the biology and ecology of this vector species is lacking. In this study, we examined the oviposition of C. insignis under laboratory conditions, monitored the development of immature stages and attempted colonization of this species.

METHODS

Live C. insignis females were collected from the field using CDC-UV-LED traps, allowed to blood-feed on live chicken and given various natural substrates for oviposition in two-choice assays. The eggs deposited were transferred to 0.3% agar slants, and the hatched larvae were provided a diet of Panagrellus redivivus Linnaeus nematodes and the development of all immature stages was monitored.

RESULTS

Culicoides insignis females exhibited an overall oviposition preference for dishes containing mud from their larval habitat as gravid females deposited a significantly higher number of eggs on these dishes (35.3 eggs/female) than on controls (17.7 eggs/female). The ovipositing females also deposited a higher percentage of eggs on substrates with habitat mud and other organically enriched muds (≥ 75.2%) compared to controls (31.0%). The larvae developed successfully to adulthood on the nematode diet, exhibiting high overall larval survival rates (85.0%). Sex ratios of the F1 generation were male biased, approximately 3:1 (male:female). Captive mating could not be induced in the F1 adults.

CONCLUSIONS

Mud from the larval habitat and other organically enriched muds provide strong oviposition cues to C. insignis under laboratory conditions. Further studies will be needed to identify the key biotic/abiotic factors influencing midge oviposition in the field. The agar/nematode method is effective for the rearing of C. insignis larvae. However, further studies will be needed to address the issue of male-biased sex ratios in the progeny and to examine the mating habits/cues of C. insignis in nature, which may provide clues towards inducing captive mating in the F1 adults.

Identifying potential candidate Culicoides spp. for the study of interactions with Candidatus Cardinium hertigii

Culicoides biting midges (Diptera: Ceratopogonidae) are vectors responsible for the transmission of several viruses of veterinary importance. Previous screens of Culicoides have described the presence of the endosymbiont Candidatus Cardinium hertigii (Bacteroidetes). However, any impacts of this microbe on vectorial capacity, akin to those conferred by Wolbachia in mosquitoes, are yet to be uncovered and await a suitable system to study Cardinium-midge interactions. To identify potential candidate species to investigate these interactions, accurate knowledge of the distribution of the endosymbiont within Culicoides populations is needed. We used conventional and nested PCR assays to screen Cardinium infection in 337 individuals of 25 Culicoides species from both Palearctic and Afrotropical regions. Infections were observed in several vector species including C. imicola and the Pulicaris complex (C. pulicaris, C. bysta, C. newsteadi and C. punctatus) with varying prevalence. Phylogenetic analysis based on the Gyrase B gene grouped all new isolates within 'group C' of the genus, a clade that has to date been exclusively described in Culicoides. Through a comparison of our results with previous screens, we suggest C. imicola and C. sonorensis represent good candidates for onward study of Cardinium-midge interactions.

Temperature and food sources influence subadult development and blood-feeding response of Culicoides obsoletus (sensu lato) under laboratory conditions

BACKGROUND

Culicoides obsoletus (s.l.) is the most abundant Culicoides species in northern Europe and an important vector of bluetongue virus and Schmallenberg virus. Nevertheless, information on its subadult life stages remains scarce and no laboratory-reared colony exists.

METHODS

C. obsoletus (s.l.) adults were collected in Belgium and transferred to the laboratory in an attempt to establish a laboratory-reared colony. C. obsoletus (s.l.) were reared from eggs to adults at different temperatures (28 °C, 24 °C, 20/16 °C) and under different food regimes.

RESULTS

The most suitable temperature for rearing seemed to be 24 °C for most developmental parameters, but resulted in a biased 3:1 male/female sex ratio. The latter could be optimized to a 1:1 sex ratio when a 20/16 °C day/night temperature gradient was applied, but rearing at these low temperature conditions resulted in significantly lower egg hatching and pupation rates and a longer subadult development time. Independent of the rearing temperature, adding dung as an additional food source during larval development resulted in a significantly higher adult emergence rate and a decrease in subadult development time. Furthermore, blood-feeding rates of field-collected C. obsoletus (s.l.) were compared for different blood sources and feeding systems. The overall blood-feeding success was low and only successful with cotton pledgets (2.7% blood-fed midges) and through a membrane system with chicken skin (3.5% blood-fed midges). Higher feeding rates were obtained on cattle blood compared to sheep blood.

CONCLUSIONS

These results will help us to determine the necessary conditions to rear a viable laboratory colony of this important vector species, although further optimization is still required.

Development and lifespan of Culicoides obsoletus s.s. (Meigen) and other livestock-associated species reared at different temperatures under laboratory conditions

Culicoides Latreille (Diptera: Ceratopogonidae) transmit arboviruses affecting wild and domestic ruminants such as bluetongue (BTV) and Schmallenberg virus (SBV). The sub-adult development and lifespan of Culicoides obsoletus s.s. (Meigen), Culicoides circumscriptus Kieffer and Culicoides paolae Boorman were examined at three different temperatures under laboratory conditions. Insects were collected from field between spring and autumn 2015 in two livestock farms located in Majorca (Spain). Gravid females were held individually at 18, 25 or 30 °C. Low temperatures increased the adult lifespan, time to oviposit and rate of development, whereas high temperatures increased the number of eggs, successful pupation and adult emergence as well as the larvae growth rate. The results showed that C. obsoletus s.s. have optimum development at 18 °C, whereas the optimal rearing temperature for C. circumscriptus and C. paolae was under warmer conditions of 25-30 °C. Variations in temperature/humidity and assays with different materials and substrates for oviposition should be considered in future studies. Understanding the requirements of the different species of Culicoides optimizing the results should be of special interest for predicting environmental change effects on these species, in addition to determining the rearing conditions for candidate Culicoides vectors.

Next-generation tools to control biting midge populations and reduce pathogen transmission

Biting midges of the genus Culicoides transmit disease-causing agents resulting in a significant economic impact on livestock industries in many parts of the world. Localized control efforts, such as removal of larval habitat or pesticide application, can be logistically difficult, expensive and ineffective if not instituted and maintained properly. With these limitations, a population-level approach to the management of Culicoides midges should be investigated as a means to replace or supplement existing control strategies. Next-generation control methods such as Wolbachia- and genetic-based population suppression and replacement are being investigated in several vector species. Here we assess the feasibility and applicability of these approaches for use against biting midges. We also discuss the technical and logistical hurdles needing to be addressed for each method to be successful, as well as emphasize the importance of addressing community engagement and involving stakeholders in the investigation and development of these approaches.

Tracking Community Timing: Pattern and Determinants of Seasonality in Culicoides (Diptera: Ceratopogonidae) in Northern Florida

Community dynamics are embedded in hierarchical spatial–temporal scales that connect environmental drivers with species assembly processes. Culicoides species are hematophagous arthropod vectors of orbiviruses that impact wild and domestic ruminants. A better sense of Culicoides dynamics over time is important because sympatric species can lengthen the seasonality of virus transmission. We tested a putative departure from the four seasons calendar in the phenology of Culicoides and the vector subassemblage in the Florida panhandle. Two years of weekly abundance data, temporal scales, persistence and environmental thresholds were analyzed using a tripartite Culicoides β-diversity based modeling approach. Culicoides phenology followed a two-season regime and was explained by stream flow and temperature, but not rainfall. Species richness fit a nested pattern where the species recruitment was maximized during spring months. Midges were active year-round, and two suspected vectors species, Culicoides venustus and Culicoides stellifer, were able to sustain and connect the seasonal modules. Persistence suggests that Orbivirus maintenance does not rely on overwintering and that viruses are maintained year-round, with the seasonal dynamics resembling subtropical Culicoides communities with temporal-overlapping between multivoltine species. Viewing Culicoides-borne orbiviruses as a time-sensitive community-based issue, our results help to recommend when management operations should be delivered.