Female Tabanus Research Articles

Guidelines for user-friendly iconographic description of hematophagous flies' external morphology; application to the identification of Tabanus rubidus (Wiedemann, 1821) (Diptera: Tabanidae)

Abstract Background The main hematophagous flies acting as mechanical vectors of pathogens in mammals are tabanids, stomoxyine flies and some hematophagous Musca spp. Species-identification using dichotomous keys is based on external morphology of the flies. Their proper use requires specific skills and confirmation by shipment of specimens to specific taxonomic area specialists. Although potentially very high (especially in tabanids: 4400 species), the species-diversity of biting flies in livestock is generally limited in a given area (on average 5–10 species). A quick and user-friendly identification would be useful to veterinary technicians to fill gaps in their knowledge and support any control program. Method Based on the facilities brought by numeric photography and the most frequent criteria used in the dichotomous entomologic keys, we generated guidelines to easily create a complete illustration of hematophagous flies external morphology, including dorsal, ventral and lateral views of whole body, head, antenna, thorax, wings, abdomen, legs and some other details, when necessary. Results Application was made through a series of 32 pictures allowing user-friendly description and identification of the female Tabanus rubidus, a common mechanical vector of pathogens in Asia. Conclusion These guidelines will help generating illustrated descriptions of hematophagous flies, which will ease their identification, even at distance. Further on, genotyping of the insects might be a nice complement. Once adopted, these guidelines might be a basis for a better knowledge of the identity, biology and ecology of the hematophagous flies encountered in livestock, and thus, for the development of adapted control measures.

An insight into the sialome of the horse fly, Tabanus bromius

Blood feeding animals face their host's defenses against tissue injury and blood loss while attempting to feed. One adaptation to surmount these barriers involves the evolution of a salivary potion that disarms their host's inflammatory and anti-hemostatic processes. The composition of the peptide moiety of this potion, or sialome (from the Greek sialo = saliva), can be deducted in part by proper interpretation of the blood feeder’ sialotranscriptome. In this work we disclose the sialome of the blood feeding adult female Tabanus bromius. Following assembly of over 75 million Illumina reads (101 nt long) 16,683 contigs were obtained from which 4078 coding sequences were extracted. From these, 320 were assigned as coding for putative secreted proteins. These 320 contigs mapped 85% of the reads. The antigen-5 proteins family was studied in detail, indicating three Tabanus specific clades with and without disintegrin domains, as well as with and without leukotriene binding domains. Defensins were also detailed; a clade of salivary tabanid peptides was found lacking the propeptide domain ending in the KR dipeptide signaling furin cleavage. Novel protein families were also disclosed. Viral transcripts were identified closely matching the Kotonkan virus capsid proteins. Full length Mariner transposases were also identified. A total of 3043 coding sequences and their protein products were deposited in Genbank. Hyperlinked excel spreadsheets containing the coding sequences and their annotation are available at http://exon.niaid.nih.gov/transcriptome/T_bromius/Tbromius-web.xlsx (hyperlinked excel spreadsheet, 11 MB) and http://exon.niaid.nih.gov/transcriptome/T_bromius/Tbromius-SA.zip (Standalone excel with all local links, 360 MB). These sequences provide for a platform from which further proteomic studies may be designed to identify salivary proteins from T. bromius that are of pharmacological interest or used as immunological markers of host exposure.

Alighting of Tabanidae and muscids on natural and simulated hosts in the Sudan

Alighting of horse flies (Diptera: Tabanidae) and non-biting muscids (Diptera: Muscidae) was studied at Khartoum, Sudan, using black cylindrical models mimicking a goat, calf and cow. Flies were intercepted by attaching electrocution grids or clear adhesive film to models. Alighting sites and defensive behaviour were also documented on hosts through observation. Female Tabanus sufis (Jennicke), T. taeniola (Palisot) and Atylotus agrestis (Wiedemann) were the main tabanids captured. Muscids landed in equal numbers on all sizes of models. They had a strong preference for the upper portions of both models and hosts. Landings of T. taeniola and A. agrestis increased with model size, but not so for T. sufis. T. taeniola and A. agrestis scarcely alighted on the legs of models whereas 60-78% of T. sufis did so. Landings of T. sufis on artificial legs did not vary with model size. Landings of all tabanids on the lower and upper portions of a model increased with model size. For both hosts and models, most tabanids (88-98%) alighted on the lower half and legs. Most muscids (63-89%) alighted on the upper half. Landing of tabanids on the cow was 34.9 and 69.3 times greater than that on the calf and goat, respectively. These results are discussed in relation to strategies for the control of blood-sucking flies associated with farm animals using either insecticide-treated live baits or their mimics.

Factors Affecting Engorgement Behavior in the Salt Marsh Horse Fly, Tabanus nigrovittatus Macquart (Diptera: Tabanidae)

Female Tabanus nigrovittatus were field collected and used in laboratory experimentation to explore physiological and behavioral factors that affect engorgement. Previous studies showed sulfakinins act as feeding satiety factors in insects. This study demonstrates that sulfakinins have differing effects on engorgement that is dependent on the feeding technique used in the laboratory. The satiety effect of sulfakinin on flies engorging using the blood-soaked Kimwipe® feeding technique is not in agreement with previous experiments using an alternate feeding technique with artificial membranes. This study is the first to demonstrate that the temperature of blood is a significant factor for engorgement in this species. Also, the percentage of flies engorging is significantly different depending on the feeding technique used.

Effect of Octenol on Engorgement by Tabanus nigrovittatus (Diptera: Tabanidae)

Adult female Tabanus nigrovittatus Macquart (Diptera: Tabanidae) were field collected from a salt marsh in Essex County, Massachusetts. The horse flies were transported back to and tested in the laboratory to determine the effects of octenol (1-octen-3-ol) on engorgement. Flies exposed to octenol strips had a significantly higher engorgement response compared with control flies. To our knowledge, this is the first study to demonstrate an important link between an odor stimulus and the feeding response in Tabanidae. Research examining the link between odor attractants and repellents on the engorgement response is lacking or limited in most hematophagous Diptera. Understanding the role odors have on ingestion is essential to knowing how to interrupt feeding behavior of blood-feeding arthropods, especially for important vectors.

Effect of Octenol on Engorgement by <I>Tabanus nigrovittatus</I> (Diptera: Tabanidae)

Adult female Tabanus nigrovittatus Macquart (Diptera: Tabanidae) were field collected from a salt marsh in Essex County, Massachusetts. The horse flies were transported back to and tested in the laboratory to determine the effects of octenol (1-octen-3-ol) on engorgement. Flies exposed to octenol strips had a significantly higher engorgement response compared with control flies. To our knowledge, this is the first study to demonstrate an important link between an odor stimulus and the feeding response in Tabanidae. Research examining the link between odor attractants and repellents on the engorgement response is lacking or limited in most hematophagous Diptera. Understanding the role odors have on ingestion is essential to knowing how to interrupt feeding behavior of blood-feeding arthropods, especially for important vectors.

Tabanus importunus, vecteur mécanique expérimental deTrypanosoma vivaxen Guyane Française

The pathogen of american bovine trypanosomiasis Trypanosoma vivax was transmitted between zebu bull calves by blood meal interruption and immediate resumption of female Tabanus importunus horse flies. Transmission was achieved by 44 transfers from the donor animal to the recipient animal carried out from 8 to 10 days after experimental inoculation of the donor animal. Parasitemia was detected in the recipient animal 10 days after transfer beginning.

Feeding responses of the horsefly, Tabanus nigrovittatus (Diptera; Tabanidae) to purinergic phagostimulants

Each year in late June, 1982–1986, the phagostimulatory potencies of purinergic compounds (ATP and derivatives of ATP) were tested on wild-caught female Tabanus nigrovittatus. In all, 15 compounds were investigated. They were dissolved in 0.15 M sodium chloride solution and presented at 37°C in an artificial feeding apparatus in which the flies fed upward through a Parafilm M ® membrane. Potencies ranked, ATP > ADP > 2′dATP > ATP-γ-S = 2′dADP > AMP-PCP = AtetraP > AMP-PNP = 2′3′dd-ATP = AMP = APS. 3′dATP, Ara-ATP, and Ado were very weak phagostimulants and c-AMP induced no gorging at 1 mM. Previous work that reported ADP > ATP was an error. The average ED 50 for ATP is 21.2 μM and ADP is 39.3 μM. Any changes in the phosphate chain of ATP caused a significant reduction in potency. Removal of the oxygen at the 3′ position on the ribose reduced potency much more than its removal at the 2′ position. Substitution of solvents other than the sodium chloride solution changed ED 50 values for ATP and ADP. Addition of 5% bovine albumin and 10 mM sodium bicarbonate to the 0.15 M sodium chloride increases the potency of ATP nearly 3-fold and the potency of ADP by more than 7-fold. ADP dissolved in choline chloride was as potent as ADP in sodium chloride solution. Addition of calcium ions to the solvent reduced the potency of ADP, probably because of the activation of apyrase enzymes. The potency of ADP was determined each year as an indicator of seasonal variability. Its ED 50 values ranged from 33.3 μM in 1982 to 45.7 μM in 1983. June 1985 was unusually cold and the ED 50 value for ADP was 92.7 μM. Data from 1985 were segregated from the other data. Seasonal effects must be considered when field-collected insects are used.

Electrophysiological Recordings from the Taste Chemosensilla of Tabanus nigrovittatus (Diptera: Tabanidae) and Determination of Behavioral Tarsal Acceptance Thresholds

A modified behavioral test for determining the median tarsal acceptance thresholds of field-collected, female Tabanus nigrovittatus Macquart to sugars showed that flies were sensitive to the three major nectar sugars (fructose, sucrose, and glucose, in that order of decreasing sensitivity) whereas galactose, a nonnectar sugar, was not comparably stimulating. Comparisons of various treatment effects on the median tarsal acceptance thresholds showed that for future studies, flies should be fed 10% sucrose before testing, should be starved for 24 h before testing, and they do not have to be pretested for a water response. Electrophysiological recordings showed that gustatory chemosensilla were located on the labellum, tip of labrum, labral food canal, foretarsi, tibia, and antennae. All chemosensilla responded to sugar and salt, whereas only those chemosensilla at the tip of the labrum and those lining the food canal, which normally contact the blood meal, responded to sera and plasma.

Activities and physiological states of male and femaleTabanus sackeni

Male and female Tabanus sackeni Fairchild (Diptera: Tabanidae) were collected on a road, dipping at pools of water on a road, and at uv-light traps; females were also caught in Malaise traps. Most males at uv-light traps were collected just before sunrise. Most females at uv-light traps were collected in the evening and most had recently taken a bloodmeal. Malaise-trapped females showed a distinct crepuscular peak of host-seeking activity. Crop volumes were variable in these host-seeking females; many had large crops. Crop volumes were small in individuals of both sexes collected dipping or on the road. Many dipping females were gravid. By examining how physiological states and the behaviour of individuals changed according to trap type, we are able to make inferences about the timing and importance of a number of unobserved activities. A link between uptake of water and sugar feeding was apparent and we postulate that mating takes place in the early morning, just before sunrise.

Genetic and Morphometric Discrimination of Coastal and Inland Tabanus lineola (Diptera: Tabanidae)

A population-genetic study of adult female Tabanus lineola F. from New Jersey and Louisiana determined that the coastal and inland “varieties” T. lineola hinellus Philip and T. lineola lineola F. are reproductively isolated and represent distinct species. Diagnostic differences were found at 4 of 11 gene loci surveyed. Nine individuals were genetically distinct from all other specimens and may represent a third cryptic species. Stepwise discriminant analysis was used to produce a taxonomic key for separation of the coastal and inland species based on four easily measured morphological characters. The degree of separation achieved was greater for specimens collected in Louisiana.

The importance of pattern in visual attraction of Tabanus nigrovittatus Macquart (Diptera: Tabanidae)

Host-seeking female Tabanus nigrovittatus Macquart primarily use visual cues to locate hosts and host mimics. The importance of various attributes of patterns to this behavior was examined in the field using black and white two-dimensional panels. Panels with a square, circle, or star of equal size were equally attractive as were panels with stars with increasingly complex edges. In a series of panels with black circles of increasing size, attraction increased as the size of the circles increased. High contour density was not important in series of panels with increasing size and decreasing number of patterns (squares or circles), and large patterns with simple edges were most attractive. Both light objects against a dark background and dark objects against a light background were highly attractive. The response of flies to objects with stripes indicated that stripes decreased attraction, possibly as a result of shape disruption. These results indicate that solid, compact, large objects with high contrast against the background were the most attractive to host-seeking flies and that fine pattern detail was not important.

Destination of the Meal and the Effect of a Previous Sugar or Blood Meal on Subsequent Feeding Behavior in Female Tabanus nigrovittatus (Diptera: Tabanidae)1

The crop was the main destination for 1 M sucrose, whereas blood ingested from a restrained rat or water fed alone and at room temperature was directed to the midgut in female Tabanus nigrovittatus Macquart. These results are consistent with previous reports for other dipteran species and for field-collected female T. nigrovittatus. Satiation on a previous meal failed to inhibit the immediate response to stimuli associated with feeding on the other substance. When two meals were taken, regardless of the sequence, the total amount ingested remained the same.

Comparative Study of the Mouthparts and Associated Sensilla of Adult Male and Female Tabanus Nigrovittatus (Diptera: Tabanidae)1

Comparisons between the mouthparts and associated sensilla of male and female Tabanus nigrovittatus showed distinct sexual dimorphism for most, but not all, structures related to the feeding habits of the sexes. In males the reduced number of sensilla and absence of denticles on the apex of the labrum, absence of mandibles, failure of salivary duct to open at the tip of the hypopharynx, and lack of retrorse teeth on the lacinia of the maxilla all correlate with the non-blood-feeding habit. In both sexes sensilla were found on all the mouthparts except the hypopharynx and maxillary lacinia. Structures previously unreported on the mouthparts of tabanids are the 2 campaniform sensilla on each mandible of the female and pseudotracheal connectors on the labium of both sexes.

Large Scale Use of Box Traps to Study and Control Saltmarsh Greenhead Flies (Diptera: Tabanidae) on Cape Cod, Massachusetts

During May and June 1970–79, ca. 300–730 box traps painted with light or dark colors were placed around the perimeters of Cape Cod salt marshes to capture green head flies ( Tabanus lineola and T. nigrovittatus ) which emerge during July and Aug. Yearly fluctuations in the average counts from a sample of 33 box traps visited weekly, generally correlated with average counts from unpainted, adhesive-smeared, square, masonite traps located at 6 sites in the experimental and 2 sites in the control marshes. These data and annual counts from ca. 40 additional box traps indicated that trap catches were related to annual variations in greenhead populations, marsh size, random movement of flies, and weather conditions rather than to the box trap colors. Over the 10- yr. period, a noticeable and measurable decrease in the nuisance level of the flies occurred around the perimeters of all marshes containing box traps. Samples of Tabanus taken from the traps were identified as 95.9% T. nigrovittatus) females, 3.6% T. lineola females, 0.4% T. lineola males, and small numbers of T. atratus females, T. nigrovittatus males, and other T. spp. None of the trapped female Tabanus which were killed and examined internally contained blood in the digestive tract, and almost 100% were parous. A list of other insects found in the box traps is given.

Further notes on Oriental Tabanidae (Diptera) V. New species of Tabanus from Southeast Asia.

Described as new from Southeast Asia are the following female Tabanus : from Viet Nam, T. perileucus, T. albocreus and T. maurus ; from Thailand, T. admelanopygus and T. cnecus ; and from Mindanao, Philippine Is., T. caligneus .

Emergence and Flight Activity of Salt-Marsh Horse Flies and Deer Flies1,2

Bionomics of 4 common Tabanidae (Diptera) was studied by use of emergence traps, Manitoba fly traps, and insect sweep-net collections. Emergence locations and sex ratios are presented. Female Tabanus nigrovittatus Macquart predominated on a New Jersey salt marsh near an upland area, apparently being concentrated by southeast breezes. The tall, dense, marsh-upland border vegetation apparently presented a geographical barrier to flight farther inland and formed an environmental trap at some locations. Aggregation to geographically pronounced locations occurred on the marsh. Many female Chrysops atlanticus Pechuman sought a blood meal on the marsh during the period of adult emergence, but those seeking blood shifted entirely from the marsh to the upland, about 150 yards from the marsh edge soon after adults had ceased emerging.