Seasonal and diurnal biting activities and zoonotic filarial infections of two Simulium species (Diptera: Simuliidae) in northern Thailand

The possible role of haematophagous flies in the incidence of bovine teat papillomatosis

The relationship between the incidence of bovine teat papillomatosis and the activity of haematophagous flies was investigated in Japan. A total of 15,737 flies consisting of 33 species were collected by dry ice-baited mosquito net (DMN) trap and a sweep net from udders of cattle. Simulium aokii (Takahasi) of Simuliidae (black flies) was the predominant species, followed by S. tobetsuense Ono and S. iwatense (Shiraki). Simulium aokii had the highest peak in October, followed by September. Numbers of blood spots from the bites per teat in nulliparous cattle were significantly correlated with numbers of S. aokii collected by DMN trap. Numbers of teats with warts and spots of blood from the bites per teat were significantly more abundant in anterior teats than posterior teats. The average incidence of teat papillomatosis in nulliparous cattle was significantly higher than that in parous cattle, and the highest incidence by month was in May, followed by April. Although bovine papillomavirus (BPV) DNA was not detected in flies examined, the presence of black flies and blood spots from their bites were associated with subsequent high incidence of growing warts. In particular, it would pay to give attention to species such as S. aokii that severely attack udders in the present locality. Further investigations for the detection of BPV DNA from flies parasitizing on teats are needed.

Discovery of the Larvae and Pupae of the Black Fly Simulium (Gomphostilbia) khelangense and Breeding Habitats of Potential Pest Species of the S. (G.) chumpornense Subgroup (Simuliidae)

Two species of black flies (Simuliidae) in Thailand, Simulium chumpornense Takaoka and Kuvangkadilok, 2000, and S. khelangense Takaoka, Srisuka & Saeung, 2022, are potent vectors of avian blood protozoa of the genera Leucocytozoon and Trypanosoma and are pests of domestic avian species. Although the adults are abundant throughout Thailand, information on their breeding habitats is limited, and the immature stages of S. khelangense are unknown. We collected the larvae and pupae of S. khelangense from the Mekong River, the first-ever record of Simuliidae from this large continental river. Mitochondrial cytochrome c oxidase I and internal transcribed spacer 2 were used to associate the larvae and pupae with known adults. Both genetic markers strongly supported their identity as S. khelangense. The larvae and pupa of S. khelangense are described. The pupal gill filaments, larval abdominal protuberances, and setae distinguish this species from other members of the S. varicorne species group. The immature stages of S. chumpornense inhabit a wide variety of flowing waters, from small streams (3 m wide) to enormous continental rivers (400 m wide); thus, S. chumpornense is a habitat generalist. In contrast, S. khelangense was found only in the large Mekong River and is, therefore, a habitat specialist. Both species can exploit their principal habitats and produce abundant adult populations.

Diversity, Distribution and Host Blood Meal Analysis of Adult Black Flies (Diptera: Simuliidae) from Thailand

Understanding the factors associated with the species diversity and distribution of insect vectors is critically important for disease epidemiology. Black flies (Diptera: Simuliidae) are significant hematophagous insects, as many species are pests and vectors that transmit pathogens to humans and other animals. Ecological factors associated with black fly species distribution have been extensively examined for the immature stages but are far less well explored for the adult stage. In this study, we collected a total of 7706 adult black fly specimens from various locations in forests, villages and animal shelters in Thailand. The integration of morphology and DNA barcoding revealed 16 black fly taxa, including Simulium yvonneae, a species first found in Vietnam, which is a new record for Thailand. The most abundant species was the Simulium asakoae complex (n = 5739, 74%), followed by S. chumpornense Takaoka and Kuvangkadilok (n = 1232, 16%). The Simulium asakoae complex was dominant in forest (3786 of 4456; 85%) and village (1774 of 2077; 85%) habitats, while S. chumpornense predominated (857 of 1175; 73%) in animal shelter areas. The Simulium asakoae complex and S. nigrogilvum Summers, which are significant pests and vectors in Thailand, occurred at a wide range of elevations, although the latter species was found mainly in high (>1000 m) mountain areas. Simulium chumpornense, S. nodosum Puri and the S. siamense Takaoka and Suzuki complex occurred predominately in low (<800 m)-elevation areas. Simulium furvum Takaoka and Srisuka; S. phurueaense Tangkawanit, Wongpakam and Pramual; and S. nr. phurueaense were only found in high (>1000 m) mountain areas. A host blood meal analysis revealed that the S. asakoae; S. chamlongi Takaoka and Suzuki; S. nigrogilvum; S. chumpornense; and the S. striatum species group were biting humans. This is the first report of the latter two species biting humans. We also found that S. chumpornense was biting turkeys, and S. chamlongi was biting chickens, which are new host blood sources recorded for these species. In addition, we found that the S. feuerborni Edwards complex was biting water buffalo, which is the first report on the biting habits of this species.

Fast-evolving nuclear genes as barcoding markers for black flies (Diptera: Simuliidae) in Thailand

Rapid and accurate identification is a prerequisite for the study of all aspects of species, particularly for pests and vectors. Black flies are economically significant blood-sucking insects, as many species are pests and vectors that transmit parasites to humans and other animals. We examined the efficiency of two fast-evolving nuclear genes, elongator complex protein 1 (ECP1) and big zinc finger (BZF), for identifying 13 nominal species in three species-groups of black flies, the Simulium multistriatum, S. striatum, and S. tuberosum groups, in Thailand where the mitochondrial cytochrome c oxidase I (COI) gene has not been successful for differentiating many nominal species. ECP1 gene sequences were highly effective for identification, with >96% (181 of 188) of the specimens correctly identified. Unsuccessful identifications based on ECP1 were between S. nakhonense and S. chiangmaiense, which are members of the S. striatum species-group, whereas all identifications of nominal species of the S. multistriatum and S. tuberosum species-groups were successful. In contrast, BZF had successful rates for the S. striatum species-group, with >93% (71 of 76) of the specimens correctly identified. This gene also successfully assigned unknown larvae of the S. striatum group to species. Phylogenetic analyses and molecular species delimitations based on the BZF gene uncovered cryptic diversity in two nominal species, S. nakhonense and S. wangkwaiense, which will require resolution through further study.

From bites to barcodes: uncovering the hidden diversity of black flies (Diptera: Simuliidae) in Vietnam

BACKGROUND

Prompt and precise identification of black flies (Simuliidae) is crucial, given their biting behaviour and significant impact on human and animal health. To address the challenges presented by morphology and chromosomes in black fly taxonomy, along with the limited availability of molecular data pertaining to the black fly fauna in Vietnam, this study employed DNA-based approaches. Specifically, we used mitochondrial and nuclear-encoded genes to distinguish nominal species of black flies in Vietnam.

METHODS

In this study, 135 mitochondrial cytochrome c oxidase subunit I (COI) sequences were established for 45 species in the genus Simulium in Vietnam, encompassing three subgenera (Gomphostilbia, Nevermannia, and Simulium), with 64 paratypes of 27 species and 16 topotypes of six species. Of these COI sequences, 71, representing 27 species, are reported for the first time.

RESULTS

Combined with GenBank sequences of specimens from Malaysia, Myanmar, Thailand, and Vietnam, a total of 234 DNA barcodes of 53 nominal species resulted in a 71% success rate for species identification. Species from the non-monophyletic Simulium asakoae, S. feuerborni, S. multistriatum, S. striatum, S. tuberosum, and S. variegatum species groups were associated with ambiguous or incorrect identifications. Pairwise distances, phylogenetics, and species delimitation analyses revealed a high level of cryptic diversity, with discovery of 15 cryptic taxa. The current study also revealed the limited utility of a fast-evolving nuclear gene, big zinc finger (BZF), in discriminating closely related, morphologically similar nominal species of the S. asakoae species group.

CONCLUSION

This study represents the first comprehensive molecular genetic analysis of the black fly fauna in Vietnam to our knowledge, providing a foundation for future research. DNA barcoding exhibits varying levels of differentiating efficiency across species groups but is valuable in the discovery of cryptic diversity.

Discovery of a new black fly species in the Simulium (Simulium) striatum species-group (Diptera: Simuliidae) from northeastern Thailand and its phylogenetic relationships with seven Thai related species

The female, male, pupa and mature larva of Simulium (Simulium) poolpholi sp. nov. collected from a large and seasonal stream in northeastern Thailand are described. This new species is placed in the S. striatum species-group by the female sternite 8 concave posteromedially in form of the inverted-U shape, ovipositor valve with a ventrally produced process along its inner margin, male ventral plate saddle-shaped, style with a basal protuberance, and pupal gill with 10 filaments. It is morphologically similar to S. (S.) phraense Takaoka, Srisuka & Saeung from northern Thailand by lacking annular ridges on the surface of pupal gill filaments but it is distinguished from the latter species by the arrangement of pupal gill filaments. Molecular analysis using the fast-evolving nuclear big zinc finger (BZF) gene shows that S. (S.) poolpholi sp. nov. formed a distinct clade, being separated from the seven other Thai species of this species-group by a genetic distance of 1.84-4.55%. Our discovery increases the number of species in the S. striatum species-group in Thailand to nine.

DNA barcoding of tropical black flies (Diptera: Simuliidae) in Thailand: One decade of progress

Black flies (Diptera: Simuliidae) are important blood sucking insects because they are the vectors of disease agents transmitted to human and other animals. Rapid and correct species identifications are necessary for all aspects of the study of black flies. DNA barcodes based on mitochondrial cytochrome c oxidase I (COI) have been effectively used for the determination of black fly species. However, the success of this method requires a large and reliable COI sequence library. In this study, 171 DNA barcoding sequences from 17 black fly species were added to NCBI GenBank database, six of these species were reported for the first time. Efficacy of DNA barcodes for species identification was examined using 1,286 sequences representing 89 nominal species of black flies in Thailand. A considerable level of success (90%) was achieved but efficiency of COI sequences for species identification was very low in the following species-groups; Simulium asakoae, S. feuerborni, S. multistriatum and S. striatum. Incomplete lineage sorting or inadequate variation of this genetic marker for differentiation of recently diverged species are the more likely explanations, and thus, more variable genetic markers are needed. Other reasons for unsuccessful DNA barcoding are imperfect taxonomy and the misidentification of sources of reference sequences. Because many new black fly species in Thailand were described recently, a reassessment of the COI sequences reported previously is necessary.

Diversity of nematodes infecting the human-biting black fly species, Simulium nigrogilvum (Diptera: Simuliidae) in central Thailand

Black flies (Diptera: Simuliidae) are known as vectors of disease agents in humans and livestock, with some species being vectors of Onchocerca volvulus, the filarial nematode that is the causative agent of human onchocerciasis. Nematode infections in adult female black flies have been reported from some areas in northern and western Thailand, but not from other regions of Thailand. In this study, wild-caught adult female black flies from the central region of Thailand were examined for infections with nematodes. Collections of adult females were carried out at Khlong Lan district, Kamphaeng Phet province, central Thailand. A molecular approach, based on the mitochondrial (cox1, 12S rRNA) and nuclear (18S rRNA) genes, was used to identify the species of nematodes recovered from the specimens collected. A total of 911 wild-caught adult black flies were collected. Simulium nigrogilvum was the most abundant species (n = 708), followed by S. doipuiense complex (n = 179), S. chamlongi (n = 11), S. umphangense (n = 10), S. chumpornense (n = 1), S. multistriatum species-group (n = 1), and S. maewongense (n = 1). Nematode infections were detected in nine specimens of S. nigrogilvum, of which two were positive for filarial worms (one worm each, infection rate 0.28%) and seven were positive for non-filarial nematodes (11 worms in total, infection rate 0.99%). The two filarial nematodes (third-stage larvae) were identified molecularly as Onchocerca species type I, while the 11 non-filarial nematodes were classified into ascaridoid (n = 2), tylenchid (n = 6) and mermithid (n = 3) nematodes. The results of this study demonstrated that adult female S. nigrogilvum were parasitized with diverse nematodes (filarial and non-filarial). Detection of the infective larvae of Onchocerca sp. type I in S. nigrogilvum confirms that occurrence of zoonotic onchocerciasis is highly possible in Thailand. Additional in-depth investigation of the morphology, life cycle and host-parasite relationship of nematodes that parasitized this black fly host is still needed.

Simulium (Gomphostilbia) aziruni: First record of a black fly (Diptera: Simuliidae) attracted to a human in Malaysia

Most female black flies in the genus Simulium are blood-sucking flies and they can cause various parasitic diseases in human and animal. A total of 94 species of black flies have been reported in Malaysia, however, their biting behavior and role as vector of infectious agents remain understudied. To fill in this knowledge gap, we attempted to survey adult black flies from field populations in Peninsular Malaysia. In a survey carried out in 2017 at Tasik Kenyir, Terengganu, three females were caught while attracted and landed on human skin. Further morphological and molecular analyses showed that the specimens were identical to Simulium (Gomphostilbia) aziruni Takaoka, Hashim & Chen of the Simulium gombakense species-group. This is the first report on a black fly species attracted to human in Malaysia which serves as a steppingstone towards in-depth studies for black flies in this region.

Community Structure, Biodiversity and Spatiotemporal Distribution of the Black Flies (Diptera: Simuliidae) Using Malaise Traps on the Highest Mountain in Thailand

Simple Summary

Black flies, also known as buffalo gnats, are major pests to humans and animals. Females of some black fly species serve as vectors for transmitting several pathogens (i.e., filarial nematodes, blood protozoa, viruses, and bacteria) to humans and animals via their bites. In Thailand, some human-biting species are considered as natural vectors of zoonotic onchocerciasis. This study was the first to contribute baseline data on the community structure, biodiversity and spatial and temporal distribution of adult black flies in tropical forests of the highest mountain in northern Thailand, Doi Inthanon National Park, by using malaise traps. Adult black flies were captured monthly at low to high elevation sites, using malaise traps across three seasons during a one-year period. A total of 44 species were identified among 9406 specimens. It was found that species richness was greatest at the mid elevation. Black fly populations peaked in the rainy season at all elevation sites. The findings of this study showed that varied elevations and seasons are important factors that influence the distribution and abundance of black flies in this region.

Abstract

Black flies form a group of small blood-sucking insects of medical and veterinary importance. This study aimed to investigate the community structure, biodiversity and spatial and temporal distribution of adult black flies in tropical rain forests, by using malaise traps in Doi Inthanon National Park, northern Thailand. Malaise traps were placed along six elevational gradients (400 m to 2500 m, above sea level) at Doi Inthanon National Park, Chiang Mai province, from December 2013 to November 2014. A total of 9406 adult female black flies belonging to five subgenera—Daviesellum (2%), Gomphostilbia (23%), Montisimulium (11%), Nevermannia (16%) and Simulium (48%)—were collected. Among 44 taxa found, S. tenebrosum complex had the highest relative abundance (11.1%), followed by the S. asakoae species-group (9.6%), the S. striatum species-group (7.7%), S. inthanonense (6.6%), S. doipuiense complex (6.4%), S. chomthongense complex (5.3%), S. chumpornense (5.1%) and S. nigrogilvum (4.1%). Two human-biting species—S. nigrogilvum and species in the S. asakoae species-group—were found in all of the collection sites with 100% species occurrence. Species richness was highest at mid elevation (1400 m), which is represented by 19 black fly species. The peak and lowest seasonal abundance was observed in the rainy and hot season, respectively. Seasonal species richness was highest in the cold season, except for that from elevation sites at 700 m, 1700 m and 2500 m. This study revealed that the malaise trap is effective in providing important data for further monitoring of the effects of environmental changes and conservation planning on the biodiversity of black flies in Doi Inthanon National Park.

Seasonal population dynamics and a role as natural vector of Leucocytozoon of black fly, Simulium chumpornense Takaoka & Kuvangkadilok

The black fly, Simulium chumpornense Takaoka & Kuvangkadilok, is suspected to be a natural vector of Leucocytozoon. In this study, seasonal variation in abundance of the adult fly and molecular detection of Leucocytozoon in S. chumpornense and in domestic chicken was investigated in northeastern Thailand. A total of 10,416 female adults were obtained by monthly collection for one year at six sampling sites. There was a peak of abundance in the dry season (March - May) when more than 74% of the specimens were collected. An increased number of suitable habitats for immature stages during the dry season is potentially a factor driving dry season abundance. Molecular genetic investigations revealed that S. chumpornense harbored the infectious stage of Leucocytozoon sp. indicating that it is a natural vector of this parasite. Blood smear screening for the parasite in domestic chickens found a considerable prevalence (52%) of Leucocytozoon spp. infections. The cytochrome b sequences of this parasite in domestic chickens comprised two lineages. One lineage was closely related to Leucocytozoon sp. found in S. chumpornense and another matched with L. schoutedeni. Therefore, S. chumpornense is a vector of Leucocytozoon sp. while L. schoutedeni is possibly transmitted by other ornithophilic black fly species.

DNA Barcoding of Simulium asakoae (Diptera: Simuliidae) From Northern Thailand

Previous studies suggested the presence of species complex in the so-called Simulium asakoae Takaoka & Davies (Diptera: Simuliidae) in Thailand due to its high morphological variability and genetic divergence. To investigate whether the true S. asakoae is present in Thailand, we performed a detailed morphological identification of S. asakoae and compared its DNA barcodes with the morphospecies S. asakoae from Myanmar and the typical S. asakoae from Malaysia. Phylogenetic analysis revealed the Thai materials analyzed in this study were indeed genetically similar with those from Myanmar and Malaysia, though genetic distances 0-2.27% were observed. We tentatively regard this divergence as intraspecific variation, and the automatic barcode gap discovery analysis further supports them as a single species.

Seasonal Filarial Infections and Their Black Fly Vectors in Chiang Mai Province, Northern Thailand

The transmission of zoonotic filarial parasites by black flies has so far been reported in the Chiang Mai and Tak provinces, Thailand, and the bites of these infected black flies can cause a rare disease—human zoonotic onchocerciasis. However, species identification of the filarial parasites and their black fly vectors in the Chiang Mai province were previously only based on a morphotaxonomic analysis. In this study, a combined approach of morphotaxonomic and molecular analyses (mitochondrial cox1, 12S rRNA, and nuclear 18S rRNA (SSU HVR-I) genes) was used to clarify the natural filarial infections in female black flies collected by using human and swine baits from two study areas (Ban Lek and Ban Pang Dang) in the Chiang Mai province from March 2018 to January 2019. A total of 805 and 4597 adult females, belonging to seven and nine black fly taxa, were collected from Ban Lek and Ban Pang Dang, respectively. At Ban Lek, four of the 309 adult females of Simulium nigrogilvum were positive for Onchocerca species type I in the hot and rainy seasons. At Ban Pang Dang, five unknown filarial larvae (belonging to the same new species) were detected in Simulium sp. in the S. varicorne species-group and in three species in the S. asakoae species-group in all seasons, and three non-filarial larvae of three different taxa were also found in three females of the S. asakoae species-group. This study is the first to molecularly identify new filarial species and their vector black fly species in Thailand.

Natural infections with larvae of Onchocerca species type I in the human-biting black fly, Simulium nigrogilvum (Diptera: Simuliidae), in western Thailand

Zoonotic onchocerciasis is a human infection caused by Onchocerca species of animal origins and transmitted by black fly vectors. The reported incidence of this disease has increased throughout the world. This study aims to clarify the vectorial roles of black fly species in zoonotic filarial transmission in Tak province, western Thailand. The integrated approach of morphological and DNA sequence-based analyses was used to identify species of both wild-caught female black flies and infective filarial larvae found in the infected black flies. All of 494 female black flies captured were identified as Simulium nigrogilvum, through scanning electron microscopy (SEM) and DNA sequence analyses based on the cytochrome c oxidase subunit I (COI) and subunit II (COII), and the fast-evolving nuclear elongation complex protein 1 (ECP1) genes. Four females of S. nigrogilvum harbored one to three third-stage larvae (infective larvae) in their thoraces, with an infection rate of 0.81% (4/494). All infective larvae were similar in morphology and size to one another, being identified as Onchocerca species type I (= O. sp. type A), a bovine filaria, originally reported from Japan, and also as O. sp. found in S. nodosum in Thailand, based on their body lengths and widths being 1,068-1,346 µm long by 25-28 µm wide, and morphological characters. Comparisons of cytochrome c oxidase subunit I (COI) and 12S rRNA sequences of mitochondrial DNA (mtDNA) and phylogenetic analyses with those of previous reports strongly supported that all larvae were O. sp. type I. This report is the first indicating the presence of O. sp. type I in Thailand and its vector being S. nigrogilvum.

Diversity and ecology of black flies in tea plantation area of Puncak Bogor, Indonesia

Black flies fauna in Indonesia has been studied extensively, however their ecology is still remaining unexplored. The study was carried out by collecting the larvae and pupae black flies in tea plantation area, Puncak Bogor. The collection sites were the streams located in 3 differents type of altitude, i.e. (1) the natural forest area (1200 m above the sea level) (P1); (2) the tea plantation area (900-1200 m asl) (P2); and (3) the housing area of the official tea plantation (900 m asl) (P3). The collection of black flies were done beweekly from July 2012 to April 2013. The result showed that 12 species of black flies were recorded which belong to one genus, Simulium s.l. and three subgenera (Nevermannia, Gomphostilbia and Simulium s.str). In P1, the area with high elevation (natural forest), it was found the most number of black flies species (11 species). In the streams around and in the tea plantation area (P2), it was found 7 species, and in P3, the official housing area, it was recorded 8 species. The analysis satistically showed that P1 was dominated by larvae and pupae of S. (S.) argyrocinctum, P2 by larvae and pupae of S. (N.) feuerborni, and P3 by S. (S.) argyrocinctum and S. (N.) feuerborni. The distribution of these species was different according to the elevation of the areas.

Characterization of IgE-binding proteins in the salivary glands of Simulium nigrogilvum (Diptera: Simuliidae)

Simulium dermatitis is an IgE-mediated skin reaction in animals and humans caused by the bites of black flies. Although Simulium nigrogilvum has been incriminated as the main human-biting black fly species in Thailand, information on its salivary allergens is lacking. Salivary gland extract of S. nigrogilvum females was subjected to sodium dodecylsulfate-polyacrylamide gel electrophoresis, and the separated components were applied onto nitrocellulose membranes for immunoblotting, which was performed by probing the protein blots with sera from 17 individuals who were allergic to the bites of S. nigrogilvum. IgE-reactive protein bands were characterized further by liquid chromatography-mass spectrometry (LC-MS/MS) analysis. Nine protein bands (79, 42, 32, 25, 24, 22, 15, 13, and 11 kDa) were recognized in the serum of the subjects. Four of the nine protein bands (32, 24, 15, and 11 kDa) showed IgE reactivity in all (100%) of the tested sera, and they were identified as salivary secreted antigen 5-related protein, salivary serine protease, erythema protein, and hypothetical secreted protein, respectively. Three other proteins, salivary serine protease (25 kDa), salivary D7 secreted protein (22 kDa), and hypothetical protein (13 kDa), reacted with > 50% of the sera. The relevance of the identified protein bands as allergens needs to be confirmed by using pure recombinant proteins, either in the in vivo skin prick test or in vitro detection of the specific IgE in the serum samples of allergic subjects. This will be useful for the rational design of component-resolved diagnosis and allergen immunotherapy for the allergy mediated by the bites of black flies.

Proteomes of the female salivary glands of Simulium nigrogilvum and Simulium nodosum, the main human-biting black flies in Thailand

Although several studies have reported pharmacological and immunological activity, as well as the role of black flies in transmitting pathogens to vertebrate hosts through salivary glands (SG) during blood feeding, SG proteomes of the anthropophilic black flies in Thailand have never been reported. Therefore, this study determined the SG proteomes of female S. nigrogilvum and S. nodosum. Sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE) and two-dimensional (2-DE) gels containing separated SG proteins of individual species were subjected to liquid chromatography-tandem mass spectrometry (LCMS/MS) and an orthologous protein search from eukaryotic organism, nematocera and simuliidae databases for total protein identification. SDS-PAGE and protein staining revealed at least 13 and 9 major protein bands in the SGs of female S. nigrogilvum and S. nodosum, respectively, as well as several minor ones. The 2-DE demonstrated a total of 56 and 41 protein spots for S. nigrogilvum and S. nodosum, respectively. Most of the proteins obtained in both species were enzymes involved in blood feeding, including proteases, apyrases, hyaluronidases, aminopeptidase and elastase. The results obtained in this study provided a new body of knowledge for a better understanding on the role of salivary gland proteins in these black fly species in Thailand.

Determining the Number of Instars in Simulium quinquestriatum (Diptera: Simuliidae) Using k-Means Clustering via the Canberra Distance

Simulium quinquestriatum Shiraki (Diptera: Simuliidae), a human-biting fly that is distributed widely across Asia, is a vector for multiple pathogens. However, the larval development of this species is poorly understood. In this study, we determined the number of instars in this pest using three batches of field-collected larvae from Guiyang, Guizhou, China. The postgenal length, head capsule width, mandibular phragma length, and body length of 773 individuals were measured, and k-means clustering was used for instar grouping. Four distance measures-Manhattan, Euclidean, Chebyshev, and Canberra-were determined. The reported instar numbers, ranging from 4 to 11, were set as initial cluster centers for k-means clustering. The Canberra distance yielded reliable instar grouping, which was consistent with the first instar, as characterized by egg bursters and prepupae with dark histoblasts. Females and males of the last cluster of larvae were identified using Feulgen-stained gonads. Morphometric differences between the two sexes were not significant. Validation was performed using the Brooks-Dyar and Crosby rules, revealing that the larval stage of S. quinquestriatum is composed of eight instars.

Five new species of the Simulium decuplum subgroup of the Simulium (Gomphostilbia) batoense species-group (Diptera: Simuliidae) from Thailand and their phylogenetic relationships

Five new species of black flies, Simulium (Gomphostilbia) chiangraiense, S. (G.) huaikaeoense, S. (G.) khaokhoense, S. (G.) maeklangense, and S. (G.) pamiangense, are described based on adults, pupae and mature larvae from Thailand. These five species are similar to one another and are placed in the S. decuplum subgroup of the S. batoense species-group by having the male fore coxae darkened, ventral plate flat and transverse; pupal gill with 10 short filaments; and larval postgenal cleft deep approaching or reaching the posterior margin of the hypostoma. Simulium (G.) chiangraiense sp. nov. and S. (G.) pamiangense sp. nov. differ from the three other new species by the much longer pupal gill filaments and darkened dorsal surface of abdominal segments 1 and 2. Taxonomic notes are provided to distinguish these five new species from five other related species. The phylogenetic positions of these new species in the S. decuplum subgroup are presented based on the mitochondrial COI gene. Simulium (G.) pamiangense sp. nov. and S. (G.) huaikaeoense sp. nov. are highly similar to each other genetically, showing a sister relationship, though they are clearly different morphologically. On the contrary, S. (G.) khaokhoense sp. nov. is distantly positioned from S. (G.) huaikaeoense nov., though it is almost indistinguishable morphologically from the latter.

New records of 13 species of black flies (Diptera: Simuliidae) from Myanmar

A faunistic survey of black flies in Shan State, central Myanmar, was carried out in 2013. A total of 16 species were collected, of which 13 species are newly recorded from Myanmar. Among 13 newly recorded species, S. (S.) chiangmaiense Takaoka & Suzuki varied in the number of pupal gill filaments from eight to 10. This survey increases the number of species of black flies from Myanmar from 8 to 23. They are classified in five subgenera of the genus Simulium: one in Asiosimulium, seven in Gomphostilbia, one in Montisimulium, two in Nevermannia and 12 in Simulium.

A new black fly species of the Simulium (Gomphostilbia) epistum species-group (Diptera: Simuliidae) from Thailand

A new species of black fly, Simulium (Gomphostilbia) isanense, is described based on females, males, pupae and mature larvae from Thailand. This new species is placed in the Simulium epistum species-group of the subgenus Gomphostilbia Enderlein. It is characterized by the pupal gill with eight filaments arranged as 3+3+2 from dorsal to ventral, of which an inner filament of the ventral pair is slightly longer than its counter filament. Taxonomic notes are provided to distinguish this new species from S. (G.) angulistylum Takaoka & Davies from Peninsular Malaysia, and three other related species. The difference between this new species and S. (G.) angulistylum is supported by genetic distances using the mitochondrial COI gene.

Two new species of Simulium (Gomphostilbia) (Diptera: Simuliidae) from Myanmar, and their phylogenetic relationships with related species in the S. asakoae species-group

Two new species of Simulium (Gomphostilbia), S. (G.) myanmarense and S. (G.) monglaense, are described from females, males, pupae and larvae from Myanmar. The two new species are placed in the S. asakoae species-group, and are similar to each other in the female and male but distinguished in the pupa by the presence or absence of an anterodorsal projection of the cocoon, and in the larva by a unique pattern of colored markings on the abdomen. Taxonomic notes are given to separate these species from related species. The COI gene sequences of both species are compared with those of eight species of the S. asakoae species-group and three species of the S. ceylonicum species-group. Both new species are most closely related to each other, further supporting their morphological classification in the S. asakoae species-group.

Biodiversity, seasonal abundance, and distribution of blackflies (Diptera: Simuliidae) in six different regions of Thailand

BACKGROUND

Blackflies are an important medical and veterinary group of small blood-sucking insects. Ninety-three blackfly species have been reported in Thailand. However, information on their biodiversity and population dynamics in each region is lacking. The main aim of this study was to assess the regional biodiversity, seasonal abundance and distribution of blackflies in six eco-geographically different regions in the country.

METHODS

Blackfly larvae and pupae were sampled monthly from 58 sites between May 2011 and April 2013. Diversity parameters, seasonal abundance, regional distribution and frequency of species occurrence in stream sites were analyzed.

RESULTS

A total of 19,456 mature larvae representing 57 species, and belonging to six subgenera in the genus Simulium Latreille (s.l.), were found. The five predominant taxa were S. fenestratum (8.6%), the S. asakoae complex (8.3%), S. nakhonense (7.5%), the S. siamense complex (7.4%) and the S. doipuiense complex (6.7%). The most frequent taxa at all sites were the S. asakoae complex (84.5%), followed by S. fenestratum (82.8%), the S. siamense complex (75.9%), S. decuplum (60.3%), S. nakhonense (58.6%) and the S. tani complex (48.3%). The richness of regional species was highest (40 species) in the north and predominated in the cold season. However, blackflies in the south predominated during the hot season. The highest numbers of blackflies collected from central, northeastern, eastern and western regions of the country were observed in the rainy season. Overall, the mean number of blackflies collected across the six regions during the rainy and cold season had no statistically significant difference, but it differed significantly in the hot season.

CONCLUSIONS

Blackflies in Thailand were surveyed in all three seasons across six geographical regions. These findings demonstrated that blackfly communities at each stream site varied with seasonality, and the regional relative abundance of blackflies differed markedly in the hot season. It was also found that the occurrence and distribution of blackflies in each region were associated strongly with elevation.

A New Black Fly Species of Simulium (Gomphostilbia) (Diptera: Simuliidae) From Thailand

Simulium (Gomphostilbia) fukudae sp. nov. is described based on females, males, pupae, and larvae from Thailand. This new species is placed in the Simulium batoense species-group of Simulium (Gomphostilbia). It is characterized by the female frons almost bare, male paramere covered with minute setae, pupal gill composed of six slender filaments, pupal terminal hooks cone-shaped, and cocoon with an anterodorsal projection. Taxonomic notes are given to separate this new species from the most similar species, Simulium (G.) sextuplum Takaoka & Davies and Simulium (G.) paukatense Takaoka, both from Malaysia.

Descriptions of the female and larva of Simulium (Gomphostilbia) udomi (Diptera: Simuliidae) from Thailand, and its transfer to the Simulium asakoae species-group

The female and larva of Simulium (Gomphostilbia) udomi Takaoka & Choochote from Thailand are described for the first time. The female of this species is similar to those of S. (G.) asakoae Takaoka & Davies from Peninsular Malaysia, Thailand, Hong Kong and Vietnam, and S. (G.) chiangdaoense Takaoka & Srisuka from Thailand. The larva of this species is similar to S. (G.) curtatum Jitklang et al. and S. (G.) nr. asakoae 2 from Thailand in having a medium-long postgenal cleft. Taxonomic notes are given to separate this species from these related species. The COI gene sequence of S. (G.) udomi is compared with those of eight species of the S. asakoae species-group and three species of the S. ceylonicum species-group. This species is transferred from the S. ceylonicum species-group to the S. asakoae species-group based on the adult female and male morphological characters, comparisons of the genetic distances and phylogenetic relationships inferred from the COI gene sequences.

A New Human-Biting Black Fly Species of Simulium (Simulium) (Diptera: Simuliidae) From Thailand

Simulium (Simulium) umphangense, a new human-biting species of black fly, is described based on females captured while attacking humans in western and central Thailand. The female of this new species is similar to those of S. (S.) indicum Becher, S. (S.) nigrogilvum Summers, and S. (S.) vanellum Huang et al. in the Simulium griseifrons species-group of the subgenus Simulium Latreille in having the frons densely covered with golden-yellow short hairs, a character rarely found in the subgenus Simulium. This new species is readily distinguished from the three related species by having a darkened fore tibia, a bare subcosta (or rarely with a few hairs), and an ovipositor valve not protruded posteriorly. Additional diagnostic characters of this new species are noted. This is the seventh human-biting species of black fly in Thailand.

Two New Species of Simulium (Gomphostilbia) (Diptera: Simuliidae) From Flores, Indonesia

Two new species, Simulium (Gomphostilbia) sunapii and S. (G.) rangatense, are described based on adults, pupae, and mature larvae from Flores, in the eastern part of the Sunda Archipelago, Indonesia. Simulium (G.) sunapii sp. nov. is placed in the S. asakoae species-group, representing the easternmost geographical record for the group in this archipelago. It is characterized by a small number of male upper-eye large facets in eight or nine vertical columns and 12 horizontal rows. Simulium (G.) rangatense sp. nov. is placed in the S. ceylonicum species-group and is characterized by the pupal gill with six filaments. This new species, together with two related species of the S. ceylonicum species-group in Flores, suggests the species radiation of this species-group might have been accompanied by a reduction of the number of pupal gill filaments from eight to four through six. Taxonomic notes are provided to distinguish these two new species from related species.

Simulium maleewongae, a New Species of Simulium (Gomphostilbia) (Diptera: Simuliidae) From Thailand

Simulium (Gomphostilbia) maleewongae sp. nov. is described based on the adult males and females, their pupal exuviae, and larvae from Thailand. This new species is placed in the Simulium gombakense species-group of Simulium (Gomphostilbia). It is characterized by the female cibarium with a cup-like appendage, male ventral plate deeply depressed ventromedially, pupal gill composed of an inflated structure and eight slender filaments, cone-shaped pupal terminal hooks, and cocoon with an anterodorsal projection. Taxonomic notes are given to separate this new species from 10 other species of the same species-group known from China, India, Malaysia, Thailand, Nepal, and Vietnam. Keys to identify all 11 species of the S. gombakense species-group are provided for females, males, pupae, and larvae.

DNA barcoding of human-biting black flies (Diptera: Simuliidae) in Thailand

Black flies (Diptera: Simuliidae) are important insect vectors and pests of humans and animals. Accurate identification, therefore, is important for control and management. In this study, we used mitochondrial cytochrome oxidase I (COI) barcoding sequences to test the efficiency of species identification for the human-biting black flies in Thailand. We used human-biting specimens because they enabled us to link information with previous studies involving the immature stages. Three black fly taxa, Simulium nodosum, S. nigrogilvum and S. doipuiense complex, were collected. The S. doipuiense complex was confirmed for the first time as having human-biting habits. The COI sequences revealed considerable genetic diversity in all three species. Comparisons to a COI sequence library of black flies in Thailand and in a public database indicated a high efficiency for specimen identification for S. nodosum and S. nigrogilvum, but this method was not successful for the S. doipuiense complex. Phylogenetic analyses revealed two divergent lineages in the S. doipuiense complex. Human-biting specimens formed a separate clade from other members of this complex. The results are consistent with the Barcoding Index Number System (BINs) analysis that found six BINs in the S. doipuiense complex. Further taxonomic work is needed to clarify the species status of these human-biting specimens.

Population genetic structure and demographic history of the black fly vector, Simulium nodosum in Thailand

An understanding of the genetic structure and diversity of vector species is crucial for effective control and management. In this study, mitochondrial DNA sequences were used to examine the genetic structure, diversity and demographic history of a black fly vector, Simulium nodosum Puri (Diptera: Simuliidae), in Thailand. A total of 145 sequences were obtained from 10 sampling locations collected across geographical ranges in the country. Low genetic diversity was found in populations of S. nodosum that could be explained by the recent population history of this species. Demographic history analysis revealed a signature of demographic expansion dating back to only 2600-5200 years ago. Recent population expansion in S. nodosum possibly followed an increase in agriculture that enabled its hosts', humans and domestic animals, densities to increase. Alternatively, the Thai populations could be a derivative of an older expansion event in the more northern populations. Mitochondrial DNA genealogy revealed no genetically divergent lineages, which agrees with the previous cytogenetic study. Genetic structure analyses found that only 27% of the pairwise comparisons were significantly different. The most likely explanation for the pattern of genetic structuring is the effect of genetic drift because of recent colonization.

Breeding habitat preference of preimaginal black flies (Diptera: Simuliidae) in Peninsular Malaysia

To investigate the breeding habitat preference of black flies, a comprehensive black fly survey was conducted for the first time in Peninsular Malaysia. Preimaginal black flies (pupae and larvae) were collected manually from 180 stream points encompassing northern, southern, central and east coast of the Peninsular Malaysia. A total of 47 black fly species were recorded in this study. The predominant species were Simulium trangense (36.7%) and Simulium angulistylum (33.3%). Relatively common species were Simulium cheongi (29.4%), Simulium tani (25.6%), Simulium nobile (16.2%), Simulium sheilae (14.5%) and Simulium bishopi (10.6%). Principal Component Analysis (PCA) of all stream variables revealed four PCs that accounted for 69.3% of the total intersite variance. Regression analysis revealed that high species richness is associated with larger, deeper, faster and higher discharge streams with larger streambed particles, more riparian vegetation and low pH (F=22.7, d.f.=1, 173; P<0.001). Relationship between species occurrence of seven common species (present in >10% of the sampling sites) was assessed. Forward logistic regression analysis indicated that four species were significantly related to the stream variables. S. nobile and S. tani prefer large, fast flowing streams with higher pH, large streambed particles and riparian trees. S. bishopi was commonly found at high elevation with cooler stream, low conductivity, higher conductivity and more riparian trees. In contrast, S. sheilae was negatively correlated with PC-2, thus, this species commonly found at low elevation, warmer stream with low conductivity and less riparian trees. The results of this study are consistent with previous studies from other geographic regions, which indicated that both physical and chemical stream conditions are the key factors for black fly ecology.

A multi-locus approach resolves the phylogenetic relationships of the Simulium asakoae and Simulium ceylonicum species groups in Malaysia: evidence for distinct evolutionary lineages

A multi-locus approach was used to examine the DNA sequences of 10 nominal species of blackfly in the Simulium subgenus Gomphostilbia (Diptera: Simuliidae) in Malaysia. Molecular data were acquired from partial DNA sequences of the mitochondria-encoded cytochrome c oxidase subunit I (COI), 12S rRNA and 16S rRNA genes, and the nuclear-encoded 18S rRNA and 28S rRNA genes. No single gene, nor the concatenated gene set, resolved all species or all relationships. However, all morphologically established species were supported by at least one gene. The multi-locus sequence analysis revealed two distinct evolutionary lineages, conforming to the morphotaxonomically recognized Simulium asakoae and Simulium ceylonicum species groups.

Seasonal biodiversity of black flies (Diptera: Simuliidae) and evaluation of ecological factors influencing species distribution at Doi Pha Hom Pok National Park, Thailand

This is the first study on the seasonal biodiversity of black flies and evaluation of ecological factors influencing their distribution at Doi Pha Hom Pok National Park, northern Thailand. Larvae were collected from six fixed-stream sites in relation to altitude gradients from May 2011 to April 2013. The water temperature, water pH, conductivity, total dissolved solids (TDS), salt, water velocity, stream width and depth, streambed particle sizes, riparian vegetation, and canopy cover were recorded from each site. Monthly collections from the six sites yielded 5475 last-instar larvae, belonging to 29 black fly species. The most frequently found species from all sites were Simulium asakoae (100%) followed by Simulium yuphae (83.3%), and Simulium chiangdaoense, Simulium gombakense, Simulium phahompokense, Simulium fruticosum, Simulium maeaiense and Simulium fenestratum (66.6%). Of the 5475 last-instar larvae, S. maeaiense (19.3%), S. chiangdaoense (15.8%) and S. asakoae (14.8%), were the three most abundant species. The Shannon diversity index (H) at the six sites with different altitudes of 2100m, 2000m, 1500m, 1400m, 700m, and 500m above mean sea level, were 2.042, 1.832, 2.158, 2.123, 1.821 and 1.822, respectively. The Shannon index and number of taxa in the cold season were higher than those in the rainy and hot seasons. Principal component analysis (PCA) indicated that at least three principal components have eigen values >1.0 and accounted for 93.5% of the total variability of ecological factors among sampling sites. The Canonical correspondence analyses (CCA) showed that most species had a trend towards altitude, canopy cover, riparian vegetation and water velocity.

A transmission model for the ecology of an avian blood parasite in a temperate ecosystem

Most of our knowledge about avian haemosporidian parasites comes from the Hawaiian archipelago, where recently introduced Plasmodiumrelictum has contributed to the extinction of many endemic avian species. While the ecology of invasive malaria is reasonably understood, the ecology of endemic haemosporidian infection in mainland systems is poorly understood, even though it is the rule rather than the exception. We develop a mathematical model to explore and identify the ecological factors that most influence transmission of the common avian parasite, Leucocytozoonfringillinarum (Apicomplexa). The model was parameterized from White-crowned Sparrow (Zonotrichialeucophrys) and S. silvestre / craigi black fly populations breeding in an alpine ecosystem. We identify and examine the importance of altricial nestlings, the seasonal relapse of infected birds for parasite persistence across breeding seasons, and potential impacts of seasonal changes in black fly emergence on parasite prevalence in a high elevation temperate system. We also use the model to identify and estimate the parameters most influencing transmission dynamics. Our analysis found that relapse of adult birds and young of the year birds were crucial for parasite persistence across multiple seasons. However, distinguishing between nude nestlings and feathered young of the year was unnecessary. Finally, due to model sensitivity to many black fly parameters, parasite prevalence and sparrow recruitment may be most affected by seasonal changes in environmental temperature driving shifts in black fly emergence and gonotrophic cycles.

Simulium (Asiosimulium) furvum, a new species of black fly (Diptera: Simuliidae) from Thailand

Simulium (Asiosimulium) furvum sp. nov. (Diptera: Simuliidae) is described from female, male, pupal, and larval specimens collected from Maewa National Park, Lampang Province, Thailand. This new species represents the fourth member of the subgenus Asiosimulium Takaoka & Chochoote, one of two small black fly subgenera endemic in the Oriental Region. It is characterized by a pear-shaped spermatheca in the female; a ventral plate in the male with a laterally compressed median keel directed ventrally and with a deep notch posteromedially, and aedeagal membrane with stout spines; and by 22 gill filaments in the pupa. Taxonomic notes are provided to separate this new species from three known species, Simulium (Asiosimulium) oblongum Takaoka & Choochote and Simulium (Asiosimulium) wanchaii Takaoka & Choochote, both from Thailand, and Simulium (Asiosimulium) suchitrae Takaoka from Nepal.